Mitotic serine/threonine kinases that contributes to the regulation of cell cycle progression. Associates with the centrosome and the spindle microtubules during mitosis and plays a critical role in various mitotic events including the establishment of mitotic spindle, centrosome duplication, centrosome separation as well as maturation, chromosomal alignment, spindle assembly checkpoint, and cytokinesis. Required for initial activation of CDK1 at centrosomes. Phosphorylates numerous target proteins, including ARHGEF2, BORA, BRCA1, CDC25B, DLGP5, HDAC6, KIF2A, LATS2, NDEL1, PARD3, PPP1R2, PLK1, RASSF1, TACC3, p53/TP53 and TPX2. Regulates KIF2A tubulin depolymerase activity. Required for normal axon formation. Plays a role in microtubule remodeling during neurite extension. Important for microtubule formation and/or stabilization. Also acts as a key regulatory component of the p53/TP53 pathway, and particularly the checkpoint-response pathways critical for oncogenic transformation of cells, by phosphorylating and stabilizating p53/TP53. Phosphorylates its own inhibitors, the protein phosphatase type 1 (PP1) isoforms, to inhibit their activity. Necessary for proper cilia disassembly prior to mitosis.
Aurora-A protein kinase, which is the product of an oncogene, is required for the assembly of a functional mitotic apparatus and the regulation of cell ploidy. Overexpression of Aurora-A in tumour cells has been correlated with cancer susceptibility and poor prognosis. Aurora-A activity is required for the recruitment of CDK1-cyclin B1 to the centrosome prior to its activation and the commitment of the cell to mitosis. In this report, we demonstrate that the CDC25B phosphatase, an activator of cyclin dependent kinases at mitosis, is phosphorylated both in vitro and in vivo by Aurora-A on serine 353 and that this phosphorylated form of CDC25B is located at the centrosome during mitosis. Knockdown experiments by RNAi confirm that the centrosome phosphorylation of CDC25B on S353 depends on Aurora-A kinase. Microinjection of antibodies against phosphorylated S353 results in a mitotic delay whilst overexpression of a S353 phosphomimetic mutant enhances the mitotic inducing effect of CDC25B. Our results demonstrate that Aurora-A phosphorylates CDC25B in vivo at the centrosome during mitosis. This phosphorylation might locally participate in the control of the onset of mitosis. These findings re-emphasise the role of the centrosome as a functional integrator of the pathways contributing to the triggering of mitosis.
Orchestrated remodelling of the cytoskeketon is prominent during neurite extension. In contrast with the extensive characterization of actin filament regulation, little is known about the dynamics of microtubules during neurite extension. Here we identify an atypical protein kinase C (aPKC)-Aurora A-NDEL1 pathway that is crucial for the regulation of microtubule organization during neurite extension. aPKC phosphorylates Aurora A at Thr 287 (T287), which augments interaction with TPX2 and facilitates activation of Aurora A at the neurite hillock, followed by phosphorylation of NDEL1 at S251 and recruitment. Suppression of aPKC, Aurora A or TPX2, or disruption of Ndel1, results in severe impairment of neurite extension. Analysis of microtubule dynamics with a microtubule plus-end marker revealed that suppression of the aPKC-Aurora A-NDEL1 pathway resulted in a significant decrease in the frequency of microtubule emanation from the microtubule organizing centre (MTOC), suggesting that Aurora A acts downstream of aPKC. These findings demonstrate a surprising role of aPKC-Aurora A-NDEL1 pathway in microtubule remodelling during neurite extension.
The Aurora kinases are a family of serine/threonine protein kinases that perform important functions during the cell cycle. Recently, it was shown that Drosophila Aurora A also regulates the asymmetric localization of Numb to the basal and the partitioning-defective (Par) complex to the apical cortex of neuroblasts by phosphorylating Par6. Here, we show that Aurora A is required for neuronal polarity. Suppression of Aurora A by RNA interference results in the loss of neuronal polarity. Aurora A interacts directly with the atypical protein kinase C binding domain of Par3 and phosphorylates it at serine 962. The phosphorylation of Par3 at serine 962 contributes to its function in the establishment of neuronal polarity.
A variety of developmental disorders have been associated with ciliary defects, yet the controls that govern cilia disassembly are largely unknown. Here we report a mouse embryonic node gene, which we named Pitchfork (Pifo). Pifo associates with ciliary targeting complexes and accumulates at the basal body during cilia disassembly. Haploinsufficiency causes a unique node cilia duplication phenotype, left-right asymmetry defects, and heart failure. This phenotype is likely relevant in humans, because we identified a heterozygous R80K PIFO mutation in a fetus with situs inversus and cystic liver and kidneys, and in patient with double-outflow right ventricle. We show that PIFO, but not R80K PIFO, is sufficient to activate Aurora A, a protooncogenic kinase that induces cilia retraction, and that Pifo/PIFO mutation causes cilia retraction, basal body liberation, and overreplication defects. Thus, the observation of a disassembly phenotype in vivo provides an entry point to understand and categorize ciliary disease. AUTHOR AUDIO:
Aurora-A, a member of the Aurora/Ipl1-related kinase family, is overexpressed in various types of cancer and considered to play critical roles in tumorigenesis. To better understand the pathological effect of Aurora-A activation, it is first necessary to elucidate the physiological functions of Aurora-A. Here, we have investigated the roles of Aurora-A in mitotic progression with the small interfering RNA, antibody microinjection, and time lapse microscopy using human cells. We demonstrated that suppression of Aurora-A by small interfering RNA caused multiple events to fail in mitosis, such as incorrect separation of centriole pairs, misalignment of chromosomes on the metaphase plate, and incomplete cytokinesis. Antibody microinjection of Aurora-A into late G2 cells induced dose-dependent failure in separation of centriole pairs at prophase, indicating that Aurora-A is essential for proper separation of centriole pairs. When we injected anti-Aurora-A antibodies into prometaphase cells that had separated their centriole pairs, chromosomes were severely misaligned on the metaphase plate, indicating that Aurora-A is required for proper movement of chromosomes on the metaphase plate. Furthermore, inhibition of Aurora-A at metaphase by microinjected antibodies prevented cells from completing cytokinesis, suggesting that Aurora-A also has important functions in late mitosis. These results strongly suggest that Aurora-A is essential for many crucial events during mitosis and that the phosphorylation of a series of substrates by Aurora-A at different stages of mitosis may promote diverse critical events in mitosis to maintain chromosome integrity in human cells.
Aurora2 is a cell cycle regulated serine/threonine protein kinase which is overexpressed in many tumor cell lines. We demonstrate that Aurora2 is regulated by phosphorylation in a cell cycle dependent manner. This phosphorylation occurs on a conserved residue, Threonine 288, within the activation loop of the catalytic domain of the kinase and results in a significant increase in the enzymatic activity. Threonine 288 resides within a consensus motif for the cAMP dependent kinase and can be phosphorylated by PKA in vitro. The protein phosphatase 1 is shown to dephosphorylate this site in vitro, and in vivo the phosphorylation of T288 is induced by okadaic acid treatment. Furthermore, we show that the Aurora2 kinase is regulated by proteasome dependent degradation and that Aurora2 phosphorylated on T288 may be targeted for degradation during mitosis. Our experiments suggest that phosphorylation of T288 is important for regulation of the Aurora2 kinase both for its activity and its stability.
The microtubule depolymerase Kif2a controls spindle assembly and dynamics and is essential for chromosome congression and segregation. Through a proteomic analysis, we identified Kif2a as a target for regulation by the Polo-like kinase Plk1. Plk1 interacts with Kif2a, but only in mitosis, in a manner dependent on its kinase activity. Plk1 phosphorylates Kif2a and enhances its depolymerase activity in vitro. Inhibition or depletion of Plk1 decreases microtubule-associated Kif2a signals and increases the spindle microtubule intensity in vivo. Interestingly, Aurora A also interacts with and phosphorylates Kif2a. Phosphorylation of Kif2a by Aurora A suppresses its depolymerase activity in vitro, and inhibition of Aurora A increases the microtubule-associated Kif2a signals and reduces the spindle microtubule intensity in vivo. Thus, Kif2a is regulated positively by Plk1 and negatively by Aurora A. We propose that this antagonistic regulation confers differential stability to microtubules in the spindle versus at the pole versus in the cytosol, and that this spatial differential stability is important for spindle assembly and function.
The mammalian cilium protrudes from the apical/lumenal surface of polarized cells and acts as a sensor of environmental cues. Numerous developmental disorders and pathological conditions have been shown to arise from defects in cilia-associated signaling proteins. Despite mounting evidence that cilia are essential sites for coordination of cell signaling, little is known about the cellular mechanisms controlling their formation and disassembly. Here, we show that interactions between the prometastatic scaffolding protein HEF1/Cas-L/NEDD9 and the oncogenic Aurora A (AurA) kinase at the basal body of cilia causes phosphorylation and activation of HDAC6, a tubulin deacetylase, promoting ciliary disassembly. We show that this pathway is both necessary and sufficient for ciliary resorption and that it constitutes an unexpected nonmitotic activity of AurA in vertebrates. Moreover, we demonstrate that small molecule inhibitors of AurA and HDAC6 selectively stabilize cilia from regulated resorption cues, suggesting a novel mode of action for these clinical agents.
Aurora kinase A (also called STK15 and BTAK) is overexpressed in many human cancers. Ectopic overexpression of aurora kinase A in mammalian cells induces centrosome amplification, chromosome instability and oncogenic transformation, a phenotype characteristic of loss-of-function mutations of p53. Here we show that aurora kinase A phosphorylates p53 at Ser315, leading to its ubiquitination by Mdm2 and proteolysis. p53 is not degraded in the presence of inactive aurora kinase A or ubiquitination-defective Mdm2. Destabilization of p53 by aurora kinase A is abrogated in the presence of mutant Mdm2 that is unable to bind p53 and after repression of Mdm2 by RNA interference. Silencing of aurora kinase A results in less phosphorylation of p53 at Ser315, greater stability of p53 and cell-cycle arrest at G2-M. Cells depleted of aurora kinase A are more sensitive to cisplatin-induced apoptosis, and elevated expression of aurora kinase A abolishes this response. In a sample of bladder tumors with wild-type p53, elevated expression of aurora kinase A was correlated with low p53 concentration. We conclude that aurora kinase A is a key regulatory component of the p53 pathway and that overexpression of aurora kinase A leads to increased degradation of p53, causing downregulation of checkpoint-response pathways and facilitating oncogenic transformation of cells.
Aurora-A, a mitotic serine/threonine kinase with oncogene characteristics, has recently drawn intense attention because of its association with the development of human cancers and its relationship with mitotic progression. Using the gene expression profiles of Aurora-A as a template to search for and compare transcriptome expression profiles in publicly accessible microarray data sets, we identified HURP (encodes hepatoma upregulated protein) as one of the best Aurora-A-correlated genes. Empirical validation indicates that HURP has several characteristics in common with Aurora-A. These two genes have similar expression patterns in hepatocellular carcinoma, liver regeneration after partial hepatectomy, and cell cycle progression and across a variety of tissues and cell lines. Moreover, Aurora-A phosphorylated HURP in vitro and in vivo. Ectopic expression of either the catalytically inactive form of Aurora-A or the HURP-4P mutant, in which the Aurora-A phosphorylation sites were replaced with Ala, resulted in HURP instability and complex disassembly. In addition, HURP-wild-type stable transfectants were capable of growing in low-serum environments whereas HURP-4P grew poorly under low-serum conditions and failed to proliferate. These studies together support the view that the ability to integrate evidence derived from microarray studies into biochemical analyses may ultimately augment our predictive power when analyzing the potential role of poorly characterized proteins. While this combined approach was simply an initial attempt to answer a range of complex biological questions, our findings do suggest that HURP is a potential oncogenic target of Aurora-A.
Polo-like kinase-1 (PLK1) is an essential mitotic kinase regulating multiple aspects of the cell division process. Activation of PLK1 requires phosphorylation of a conserved threonine residue (Thr 210) in the T-loop of the PLK1 kinase domain, but the kinase responsible for this has not yet been affirmatively identified. Here we show that in human cells PLK1 activation occurs several hours before entry into mitosis, and requires aurora A (AURKA, also known as STK6)-dependent phosphorylation of Thr 210. We find that aurora A can directly phosphorylate PLK1 on Thr 210, and that activity of aurora A towards PLK1 is greatly enhanced by Bora (also known as C13orf34 and FLJ22624), a known cofactor for aurora A (ref. 7). We show that Bora/aurora-A-dependent phosphorylation is a prerequisite for PLK1 to promote mitotic entry after a checkpoint-dependent arrest. Importantly, expression of a PLK1-T210D phospho-mimicking mutant partially overcomes the requirement for aurora A in checkpoint recovery. Taken together, these data demonstrate that the initial activation of PLK1 is a primary function of aurora A.
Increased Aurora A expression occurs in a variety of human cancers and induces chromosomal abnormalities during mitosis associated with tumor initiation and progression. MLN8054 is a selective small-molecule Aurora A kinase inhibitor that has entered Phase I clinical trials for advanced solid tumors. MLN8054 inhibits recombinant Aurora A kinase activity in vitro and is selective for Aurora A over the family member Aurora B in cultured cells. MLN8054 treatment results in G(2)/M accumulation and spindle defects and inhibits proliferation in multiple cultured human tumor cells lines. Growth of human tumor xenografts in nude mice was dramatically inhibited after oral administration of MLN8054 at well tolerated doses. Moreover, the tumor growth inhibition was sustained after discontinuing MLN8054 treatment. In human tumor xenografts, MLN8054 induced mitotic accumulation and apoptosis, phenotypes consistent with inhibition of Aurora A. MLN8054 is a selective inhibitor of Aurora A kinase that robustly inhibits growth of human tumor xenografts and represents an attractive modality for therapeutic intervention of human cancers.
Aurora kinase-A and -B are key regulators of the cell cycle and tumorigenesis. It has remained a mystery why these 2 Aurora kinases, although highly similar in protein sequence and structure, are distinct in subcellular localization and function. Here, we report the striking finding that a single amino acid residue is responsible for these differences. We replaced the Gly-198 of Aurora-A with the equivalent residue Asn-142 of Aurora-B and found that in HeLa cells, Aurora-A(G198N) was recruited to the inner centromere in metaphase and the midzone in anaphase, reminiscent of the Aurora-B localization. Moreover, Aurora-A(G198N) compensated for the loss of Aurora-B in chromosome misalignment and cell premature exit from mitosis. Furthermore, Aurora-A(G198N) formed a complex with the Aurora-B partners, INCENP and Survivin, and its localization depended on this interaction. Aurora-A(G198N) phosphorylated the Aurora-B substrates INCENP and Survivin in vitro. Therefore, we propose that the presence of Gly or Asn at a single site assigns Aurora-A and -B to their respective partners and thus to their distinctive subcellular localizations and functions.
Various mitotic events are controlled by Cdc2-cyclin B and other mitotic kinases. Aurora/Ipl1-related mitotic kinases were proved to play key roles in mitotic progression in diverse lower organisms. Aurora-A is a mammalian counterpart of aurora/Ipl1-related kinases and is thought to be a potential oncogene. However, the regulation of aurora-A activation and the commitment of aurora-A in the progression of G2-M phase are largely unknown in mammalian cells.
Genetic and biochemical studies in lower eukaryotes have identified several proteins that ensure accurate segregation of chromosomes. These include the Drosophila aurora and yeast Ipl1 kinases that are required for centrosome maturation and chromosome segregation. We have identified two human homologues of these genes, termed aurora1 and aurora2, that encode cell-cycle-regulated serine/threonine kinases. Here we demonstrate that the aurora2 gene maps to chromosome 20q13, a region amplified in a variety of human cancers, including a significant number of colorectal malignancies. We propose that aurora2 may be a target of this amplicon since its DNA is amplified and its RNA overexpressed, in more than 50% of primary colorectal cancers. Furthermore, overexpression of aurora2 transforms rodent fibroblasts. These observations implicate aurora2 as a potential oncogene in many colon, breast and other solid tumors, and identify centrosome-associated proteins as novel targets for cancer therapy.
Breast cancer-associated gene 1 (BRCA1) regulates the duplication and the function of centrosomes in breast cells. We have previously shown that BRCA1 ubiquitin ligase activity directly inhibits centrosome-dependent microtubule nucleation. However, there is a paradox because centrosome microtubule nucleation potential is highest during mitosis, a phase when BRCA1 is most abundant at the centrosome. In this study, we resolve this conundrum by testing whether centrosomes from cells in M phase are regulated differently by BRCA1 when compared with other phases of the cell cycle. We observed that BRCA1-dependent inhibition of centrosome microtubule nucleation was high in S phase but was significantly lower during M phase. The cell cycle-specific effects of BRCA1 on centrosome-dependent microtubule nucleation were detected in living cells and in cell-free experiments using centrosomes purified from cells at specific stages of the cell cycle. We show that Aurora-A kinase modulates the BRCA1 inhibition of centrosome function by decreasing the E3 ubiquitin ligase activity of BRCA1. In addition, dephosphorylation of BRCA1 by protein phosphatase 1 alpha enhances the E3 ubiquitin ligase activity of BRCA1. These observations reveal that the inhibition of centrosome microtubule nucleation potential by the BRCA1 E3 ubiquitin ligase is controlled by Aurora-A kinase and protein phosphatase 1 alpha-mediated phosphoregulation through the different phases of the cell cycle.
Aurora family kinases contribute to regulation of mitosis. Using RNA interference in synchronized HeLa cells, we now show that Aurora-A is required for mitotic entry. We found that initial activation of Aurora-A in late G2 phase of the cell cycle is essential for recruitment of the cyclin B1-Cdk1 complex to centrosomes, where it becomes activated and commits cells to mitosis. A two-hybrid screen identified the LIM protein Ajuba as an Aurora-A binding protein. Ajuba and Aurora-A interact in mitotic cells and become phosphorylated as they do so. In vitro analyses revealed that Ajuba induces the autophosphorylation and consequent activation of Aurora-A. Depletion of Ajuba prevented activation of Aurora-A at centrosomes in late G2 phase and inhibited mitotic entry. Overall, our data suggest that Ajuba is an essential activator of Aurora-A in mitotic commitment.
STK15 is an Aurora/Ipl-1 related serine/threonine kinase that is associated with centrosomes and induces aneuploidy when overexpressed in mammalian cells. It is well known that phosphorylation and dephosphorylation of kinases are important for regulation of their activity. But mechanisms by which STK15 activity is regulated have not been elucidated. We report that STK15 contains two functional binding sites for protein phosphatase type 1 (PP1), and the binding of these proteins is cell cycle-regulated peaking at mitosis. Activated STK15 at mitosis phosphorylates PP1 and inhibits PP1 activity in vitro. In vivo, PP1 activity co-immunoprecipitated with STK15 is also reduced. These data indicate that STK15 inhibits PP1 activity during mitosis. Also, PP1 is shown to dephosphorylate active STK15 and abolish its activity in vitro. Furthermore, we show that non-binding mutants of STK15 for PP1 are superphosphorylated, but their kinase activities are markedly reduced. Cells transfected with these non-binding mutants manifest aberrant chromosome alignment during mitosis. Our results suggest that a feedback regulation through phosphorylation/dephosphorylation events between STK15 kinase and PP1 phosphatase operates through the cell cycle. Deregulation of this balance may contribute to anomalous segregation of chromosomes during mitotic progression of cancer cells.
Aurora-A/BTAK/STK15 localizes to the centrosome in the G(2)-M phase, and its kinase activity regulates the G(2) to M transition of the cell cycle. Previous studies have shown that the BRCA1 breast cancer tumor suppressor also localizes to the centrosome and that BRCA1 inactivation results in loss of the G(2)-M checkpoint. We demonstrate here that Aurora-A physically binds to and phosphorylates BRCA1. Biochemical analysis showed that BRCA1 amino acids 1314-1863 binds to Aurora-A. Site-directed mutagenesis indicated that Ser(308) of BRCA1 is phosphorylated by Aurora-A in vitro. Anti-phospho-specific antibodies against Ser(308) of BRCA1 demonstrated that Ser(308) is phosphorylated in vivo. Phosphorylation of Ser(308) increased in the early M phase when Aurora-A activity also increases; these effects could be abolished by ionizing radiation. Consistent with these observations, acute loss of Aurora-A by small interfering RNA resulted in reduced phosphorylation of BRCA1 Ser(308), and transient infection of adenovirus Aurora-A increased Ser(308) phosphorylation. Mutation of a single phosphorylation site of BRCA1 (S308N), when expressed in BRCA1-deficient mouse embryo fibroblasts, decreased the number of cells in the M phase to a degree similar to that with wild type BRCA1-mediated G(2) arrest induced by DNA damage. We propose that BRCA1 phosphorylation by Aurora-A plays a role in G(2) to M transition of cell cycle.
Human Lats2, a novel serine/threonine kinase, is a member of the Lats kinase family that includes the Drosophila tumour suppressor lats/warts. Lats1, a counterpart of Lats2, is phosphorylated in mitosis and localized to the mitotic apparatus. However, the regulation, function and intracellular distribution of Lats2 remain unclear. Here, we show that Lats2 is a novel phosphorylation target of Aurora-A kinase. We first showed that the phosphorylated residue of Lats2 is S83 in vitro. Antibody that recognizes this phosphorylated S83 indicated that the phosphorylation also occurs in vivo. We found that Lats2 transiently interacts with Aurora-A, and that Lats2 and Aurora-A co-localize at the centrosomes during the cell cycle. Furthermore, we showed that the inhibition of Aurora-A-induced phosphorylation of S83 on Lats2 partially perturbed its centrosomal localization. On the basis of these observations, we conclude that S83 of Lats2 is a phosphorylation target of Aurora-A and this phosphorylation plays a role of the centrosomal localization of Lats2.
The optimization of a series of 5-phenylacetyl 1,4,5,6-tetrahydropyrrolo[3,4-c]pyrazole derivatives toward the inhibition of Aurora kinases led to the identification of compound 9d. This is a potent inhibitor of Aurora kinases that also shows low nanomolar potency against additional anticancer kinase targets. Based on its high antiproliferative activity on different cancer cell lines, favorable chemico-physical and pharmacokinetic properties, and high efficacy in in vivo tumor models, compound 9d was ultimately selected for further development.
Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionUniProtKB
A variety of developmental disorders have been associated with ciliary defects, yet the controls that govern cilia disassembly are largely unknown. Here we report a mouse embryonic node gene, which we named Pitchfork (Pifo). Pifo associates with ciliary targeting complexes and accumulates at the basal body during cilia disassembly. Haploinsufficiency causes a unique node cilia duplication phenotype, left-right asymmetry defects, and heart failure. This phenotype is likely relevant in humans, because we identified a heterozygous R80K PIFO mutation in a fetus with situs inversus and cystic liver and kidneys, and in patient with double-outflow right ventricle. We show that PIFO, but not R80K PIFO, is sufficient to activate Aurora A, a protooncogenic kinase that induces cilia retraction, and that Pifo/PIFO mutation causes cilia retraction, basal body liberation, and overreplication defects. Thus, the observation of a disassembly phenotype in vivo provides an entry point to understand and categorize ciliary disease. AUTHOR AUDIO:
Evidence
2:
Inferred from Physical InteractionIntAct
Elevated Aurora kinase-A expression is correlated with abrogation of DNA damage-induced apoptotic response and mitotic spindle assembly checkpoint (SAC) override in human tumor cells. We report that Aurora-A phosphorylation of p73 at serine235 abrogates its transactivation function and causes cytoplasmic sequestration in a complex with the chaperon protein mortalin. Aurora-A phosphorylated p73 also facilitates inactivation of SAC through dissociation of the MAD2-CDC20 complex in cells undergoing mitosis. Cells expressing phosphor-mimetic mutant (S235D) of p73 manifest altered growth properties, resistance to cisplatin- induced apoptosis, as well as premature dissociation of the MAD2-CDC20 complex, and accelerated mitotic exit with SAC override in the presence of spindle damage. Elevated cytoplasmic p73 in Aurora-A overexpressing primary human tumors corroborates the experimental findings.
Evidence
3:
Inferred from Physical InteractionUniProtKB
Aurora family kinases play pivotal roles in several steps during mitosis. Specifically, Aurora A kinase is an important regulator of bipolar mitotic spindle formation and chromosome segregation. Like other members of the Aurora family, Aurora A kinase is also regulated by post-translational modifications. Here, we show that a previously undescribed E3 ligase component belonging to the SCF (Skp-Cullin1-F-box protein) E3 ligase family, SCFFBXL7, impairs cell proliferation by mediating Aurora A polyubiquitination and degradation. Both Aurora A and FBXL7 co-localize within the centrosome during spindle formation. FBXL7 ectopic expression led to G(2)/M phase arrest in transformed epithelia, resulting in the appearance of tetraploidy and mitotic arrest with circular monopolar spindles and multipolar spindle formation. Interestingly, FBXL7 specifically interacts with Aurora A during mitosis but not in interphase, suggesting a regulatory role for FBXL7 in controlling Aurora A abundance during mitosis.
Evidence
4:
Inferred from Physical InteractionIntAct
Members of sirtuin family regulate multiple critical biological processes, yet their role in carcinogenesis remains controversial. To investigate the physiological functions of SIRT2 in development and tumorigenesis, we disrupted Sirt2 in mice. We demonstrated that SIRT2 regulates the anaphase-promoting complex/cyclosome activity through deacetylation of its coactivators, APC(CDH1) and CDC20. SIRT2 deficiency caused increased levels of mitotic regulators, including Aurora-A and -B that direct centrosome amplification, aneuploidy, and mitotic cell death. Sirt2-deficient mice develop gender-specific tumorigenesis, with females primarily developing mammary tumors, and males developing more hepatocellular carcinoma (HCC). Human breast cancers and HCC samples exhibited reduced SIRT2 levels compared with normal tissues. These data demonstrate that SIRT2 is a tumor suppressor through its role in regulating mitosis and genome integrity.
Evidence
5:
Inferred from Physical InteractionUniProtKB
Aurora kinases have evolved as a new family of mitotic centrosome- and microtubule-associated kinases that regulate the structure and function of centrosomes and spindle. One of its members, Aurora-A, is a potential oncogene. Overexpression of Aurora-A is also implicated in defective centrosome duplication and segregation, leading to aneuploidy and tumorigenesis in various cancer cell types. However, the regulatory pathways for mammalian Aurora-A are not well understood. Exploiting the lethal phenotype associated with the overexpression of Aurora-A in yeast, we performed a dosage suppressor screen in yeast and report here the identification of a novel negative regulator of Aurora-A, named AIP (Aurora-A kinase Interacting Protein). AIP is a ubiquitously expressed nuclear protein that interacts specifically with human Aurora-A in vivo. Ectopic expression of AIP with Aurora-A in NIH 3T3 and COS cells results in the down-regulation of ectopically expressed Aurora-A protein levels, and this down-regulation is demonstrated to be the result of destabilization of Aurora-A through a proteasome-dependent protein degradation pathway. A noninteracting deletion mutant of AIP does not down-regulate Aurora-A protein, suggesting that the interaction is important for the protein degradation. AIP could therefore be a potential useful target gene for anti-tumor drugs.
Evidence
6:
Inferred from Physical InteractionUniProtKB
To assemble mitotic spindles, cells nucleate microtubules from a variety of sources including chromosomes and centrosomes. We know little about how the regulation of microtubule nucleation contributes to spindle bipolarity and spindle size. The Aurora A kinase activator TPX2 is required for microtubule nucleation from chromosomes as well as for spindle bipolarity. We use bacterial artificial chromosome-based recombineering to introduce point mutants that block the interaction between TPX2 and Aurora A into human cells. TPX2 mutants have very short spindles but, surprisingly, are still bipolar and segregate chromosomes. Examination of microtubule nucleation during spindle assembly shows that microtubules fail to nucleate from chromosomes. Thus, chromosome nucleation is not essential for bipolarity during human cell mitosis when centrosomes are present. Rather, chromosome nucleation is involved in spindle pole separation and setting spindle length. A second Aurora A-independent function of TPX2 is required to bipolarize spindles.
Evidence
7:
Inferred from Physical InteractionIntAct
In human neuroblastoma, amplification of the MYCN gene predicts poor prognosis and resistance to therapy. In a shRNA screen of genes that are highly expressed in MYCN-amplified tumors, we have identified AURKA as a gene that is required for the growth of MYCN-amplified neuroblastoma cells but largely dispensable for cells lacking amplified MYCN. Aurora A has a critical function in regulating turnover of the N-Myc protein. Degradation of N-Myc requires sequential phosphorylation by cyclin B/Cdk1 and Gsk3. N-Myc is therefore degraded during mitosis in response to low levels of PI3-kinase activity. Aurora A interacts with both N-Myc and the SCF(Fbxw7) ubiquitin ligase that ubiquitinates N-Myc and counteracts degradation of N-Myc, thereby uncoupling N-Myc stability from growth factor-dependent signals.
Evidence
8:
Inferred from Physical InteractionUniProtKB
Int. J. Oncol. 37, 429-436 (2010)[PubMed:20596670]
Aurora-A is involved in chromosome alignment, centrosome maturation, mitotic spindle assembly and regards to an oncogene. Aurora-A is also known to bind to several other proteins affecting its up-regulation or down-regulation and localization. However, how these different binding signals work together to regulate Aurora-A is not properly known. To explore more Aurora-A interacting proteins, the low-copy yeast two-hybrid screening using Aurora-A as bait protein was performed. One novel gene, AIBp, was demonstrated to associate with Aurora-A by the yeast two-hybrid method and in vitro GST pull-down assay. Molecular characterization showed that AIBp possessed a binding site at the C-terminal with Aurora-A (kinase domain). Interestingly, AIBp also interacts with hNinein at the N-terminal, which overlaps with a previously reported hNinein and GSK3beta binding site. Using a kinase assay, AIBp interacts with the Aurora-A kinase domain functions as a positive regulator, whereas AIBp binding to hNinein appears to block the phosphorylation of hNinein by both Aurora-A and GSK3beta. siRNA-mediated elimination of AIBp from HeLa cells, results in a doughnut-like shape, asymmetrical spindle pole and multiple spindle pole formation. We also demonstrated that both AIBp and Aurora-A are co-overexpressed in various brain tumors. These studies demonstrate that AIBp may not only be required for the dynamic movement of Aurora-A at the centrosomes and spindle apparatus during the cell cycle, but may also be important during brain tumorigenesis.
Evidence
9:
Inferred from Physical InteractionUniProtKB
VX-680, also known as MK-0457, is an ATP-competitive small molecule inhibitor of the Aurora kinases that has entered phase II clinical trials for the treatment of cancer. We have solved the cocrystal structure of AurA/TPX2/VX-680 at 2.3 A resolution. In the crystal structure, VX-680 binds to the active conformation of AurA. The glycine-rich loop in AurA adopts a unique bent conformation, forming a pi-pi interaction with the phenyl group of VX-680. In contrast, in the published AurA/VX-680 structure, VX-680 binds to AurA in the inactive conformation, interacting with a hydrophobic pocket only present in the inactive conformation. These data suggest that TPX2, a protein cofactor, can alter the binding mode of VX-680 with AurA. More generally, the presence of physiologically relevant cofactor proteins can alter the kinetics, binding interactions, and inhibition of enzymes, and studies with these multiprotein complexes may be beneficial to the discovery and optimization of enzyme inhibitors as therapeutic agents.
Evidence
10:
Inferred from Physical InteractionUniProtKB
Polo-like kinase 1 (Plk1) and Aurora A play key roles in centrosome maturation, spindle assembly, and chromosome segregation during cell division. Here we show that the functions of these kinases during early mitosis are coordinated through Bora, a partner of Aurora A first identified in Drosophila. Depletion of human Bora (hBora) results in spindle defects, accompanied by increased spindle recruitment of Aurora A and its partner TPX2. Conversely, hBora overexpression induces mislocalization of Aurora A and monopolar spindle formation, reminiscent of the phenotype seen in Plk1-depleted cells. Indeed, Plk1 regulates hBora. Following Cdk1-dependent recruitment, Plk1 triggers hBora destruction by phosphorylating a recognition site for SCF(Beta-TrCP). Plk1 depletion or inhibition results in a massive accumulation of hBora, concomitant with displacement of Aurora A from spindle poles and impaired centrosome maturation, but remarkably, co-depletion of hBora partially restores Aurora A localization and bipolar spindle formation. This suggests that Plk1 controls Aurora A localization and function by regulating cellular levels of hBora.
Evidence
11:
Inferred from Physical InteractionBHF-UCL
Mutations in protein kinases can drive cancer through alterations of the kinase activity or by uncoupling kinase activity from regulation. Changes to protein expression in Aurora A, a mitotic Ser/Thr kinase, are associated with the development of several human cancers, but the effects of somatic cancer-associated mutations have not been determined. In this study we show that Aurora A kinase activity is altered in different ways in three somatic cancer-associated mutations located within the catalytic domain; Aurora A(V174M) shows constitutively increased kinase activity, Aurora A(S155R) activity is decreased primarily due to misregulation, and Aurora A(S361*) activity is ablated due to loss of structural integrity. These alterations suggest vastly different mechanisms for the role of these three mutations in human cancer. We have further characterized the Aurora A(S155R) mutant protein, found that its reduced cellular activity and mislocalization are due to loss of interaction with TPX2, and deciphered the structural basis of the disruption at 2.5 A resolution. Previous studies have shown that disruption of the Aurora A/TPX2 interaction results in defective spindles that generate chromosomal abnormalities. In a panel of 40 samples from microsatellite instability-positive colon cancer patients, we found one example in which the tumor contained only Aurora A(S155R), whereas the normal tissue contained only wild-type Aurora A. We propose that the S155R mutation is an example of a somatic mutation associated with this tumor type, albeit at modest frequency, that could promote aneuploidy through the loss of regulated interactions between Aurora A and its protein partners.
Evidence
12:
Inferred from Physical InteractionUniProtKB
Aurora-A, a mitotic serine/threonine kinase with oncogene characteristics, has recently drawn intense attention because of its association with the development of human cancers and its relationship with mitotic progression. Using the gene expression profiles of Aurora-A as a template to search for and compare transcriptome expression profiles in publicly accessible microarray data sets, we identified HURP (encodes hepatoma upregulated protein) as one of the best Aurora-A-correlated genes. Empirical validation indicates that HURP has several characteristics in common with Aurora-A. These two genes have similar expression patterns in hepatocellular carcinoma, liver regeneration after partial hepatectomy, and cell cycle progression and across a variety of tissues and cell lines. Moreover, Aurora-A phosphorylated HURP in vitro and in vivo. Ectopic expression of either the catalytically inactive form of Aurora-A or the HURP-4P mutant, in which the Aurora-A phosphorylation sites were replaced with Ala, resulted in HURP instability and complex disassembly. In addition, HURP-wild-type stable transfectants were capable of growing in low-serum environments whereas HURP-4P grew poorly under low-serum conditions and failed to proliferate. These studies together support the view that the ability to integrate evidence derived from microarray studies into biochemical analyses may ultimately augment our predictive power when analyzing the potential role of poorly characterized proteins. While this combined approach was simply an initial attempt to answer a range of complex biological questions, our findings do suggest that HURP is a potential oncogenic target of Aurora-A.
Mutations in protein kinases can drive cancer through alterations of the kinase activity or by uncoupling kinase activity from regulation. Changes to protein expression in Aurora A, a mitotic Ser/Thr kinase, are associated with the development of several human cancers, but the effects of somatic cancer-associated mutations have not been determined. In this study we show that Aurora A kinase activity is altered in different ways in three somatic cancer-associated mutations located within the catalytic domain; Aurora A(V174M) shows constitutively increased kinase activity, Aurora A(S155R) activity is decreased primarily due to misregulation, and Aurora A(S361*) activity is ablated due to loss of structural integrity. These alterations suggest vastly different mechanisms for the role of these three mutations in human cancer. We have further characterized the Aurora A(S155R) mutant protein, found that its reduced cellular activity and mislocalization are due to loss of interaction with TPX2, and deciphered the structural basis of the disruption at 2.5 A resolution. Previous studies have shown that disruption of the Aurora A/TPX2 interaction results in defective spindles that generate chromosomal abnormalities. In a panel of 40 samples from microsatellite instability-positive colon cancer patients, we found one example in which the tumor contained only Aurora A(S155R), whereas the normal tissue contained only wild-type Aurora A. We propose that the S155R mutation is an example of a somatic mutation associated with this tumor type, albeit at modest frequency, that could promote aneuploidy through the loss of regulated interactions between Aurora A and its protein partners.
Aurora-A is an oncogenic kinase essential for mitotic spindle assembly. It is activated by phosphorylation and by the microtubule-associated protein TPX2, which also localizes the kinase to spindle microtubules. We have uncovered the molecular mechanism of Aurora-A activation by determining crystal structures of its phosphorylated form both with and without a 43 residue long domain of TPX2 that we identified as fully functional for kinase activation and protection from dephosphorylation. In the absence of TPX2, the Aurora-A activation segment is in an inactive conformation, with the crucial phosphothreonine exposed and accessible for deactivation. Binding of TPX2 triggers no global conformational changes in the kinase but pulls on the activation segment, swinging the phosphothreonine into a buried position and locking the active conformation. The recognition between Aurora-A and TPX2 resembles that between the cAPK catalytic core and its flanking regions, suggesting this molecular mechanism may be a recurring theme in kinase regulation.
Interacting selectively and non-covalently with a protein kinase, any enzyme that catalyzes the transfer of a phosphate group, usually from ATP, to a protein substrate.
Evidence
1:
Inferred from Physical InteractionUniProtKB
Polo-like kinase-1 (PLK1) is an essential mitotic kinase regulating multiple aspects of the cell division process. Activation of PLK1 requires phosphorylation of a conserved threonine residue (Thr 210) in the T-loop of the PLK1 kinase domain, but the kinase responsible for this has not yet been affirmatively identified. Here we show that in human cells PLK1 activation occurs several hours before entry into mitosis, and requires aurora A (AURKA, also known as STK6)-dependent phosphorylation of Thr 210. We find that aurora A can directly phosphorylate PLK1 on Thr 210, and that activity of aurora A towards PLK1 is greatly enhanced by Bora (also known as C13orf34 and FLJ22624), a known cofactor for aurora A (ref. 7). We show that Bora/aurora-A-dependent phosphorylation is a prerequisite for PLK1 to promote mitotic entry after a checkpoint-dependent arrest. Importantly, expression of a PLK1-T210D phospho-mimicking mutant partially overcomes the requirement for aurora A in checkpoint recovery. Taken together, these data demonstrate that the initial activation of PLK1 is a primary function of aurora A.
Catalysis of the reactions: ATP + a protein serine = ADP + protein serine phosphate; ATP + a protein threonine = ADP + protein threonine phosphate; and ATP + a protein tyrosine = ADP + protein tyrosine phosphate.
The centrosome, also known as the microtubule organizing center of the cell, is a membrane-less organelle composed of a pair of barrel-shaped centrioles surrounded by electron-dense pericentriolar material. The centrosome progresses through the centrosome cycle in step with the cell cycle such that centrosomes are duplicated in time to serve as the spindle poles during mitosis and that each resultant daughter cell contains a single centrosome. Regulation of the centrosome cycle with relation to the cell cycle is an essential process to maintain the ratio of one centrosome per new daughter cell. Numerous mitosis-specific kinases have been implicated in this regulation, and phosphorlyation plays an important role in coordinating the centrosome and cell cycles. Centrosome amplification can occur when the cycles are uncoupled, and this amplification is associated with cancer and with an increase in the levels of chromosomal instability. The aurora kinases A, B, and C are serine/threonine kinases that are active during mitosis. Aurora A is associated with centrosomes, being localized at the centrosome just prior to the onset of mitosis and for the duration of mitosis. Overexpression of aurora A leads to centrosome amplification and cellular transformation. The activity of aurora A is regulated by phosphorlyation and proteasomal degradation.
The progression of biochemical and morphological phases and events that occur in a cell during successive cell replication or nuclear replication events. Canonically, the cell cycle comprises the replication and segregation of genetic material followed by the division of the cell, but in endocycles or syncytial cells nuclear replication or nuclear division may not be followed by cell division.
The molecular mechanisms by which the anti-HER2 antibodies trastuzumab and its murine equivalent 4D5 inhibit tumor growth and potentiate chemotherapy are not fully understood. Inhibition of signaling through the phosphatidylinositol 3-kinase (PI3K)-AKT pathway may be particularly important. Treatment of breast cancer cells that overexpress HER2 with trastuzumab inhibited HER2-HER3 association, decreased PDK1 activity, reduced Thr-308 and Ser-473 phosphorylation of AKT, and reduced AKT enzymatic activity. To place the role of PI3K-AKT in perspective, gene expression was studied by using Affymetrix microarrays and real time reverse transcription-PCR. Sixteen genes were consistently down-regulated 2.0-4.9-fold in two antibody-treated breast cancer cell lines. Fourteen of the 16 genes were involved in three major functional areas as follows: 7 in cell cycle regulation, particularly of the G(2)-M; 5 in DNA repair/replication; and 2 in modifying chromatin structure. Of the 16 antibody-regulated genes, 64% had roles in cell growth/maintenance and 52% contributed to the cell cycle. Direct inhibition of PI3K with an inhibitor markedly reduced expression of 14 genes that were also affected by the antibody. Constitutive activation of AKT1 blocked the effect of the anti-HER2 antibody on cell cycle arrest and on eight differentially expressed genes. The antibody enhanced docetaxel-induced growth inhibition but did not increase the fraction of apoptotic cells induced with docetaxel alone. In contrast, the antibody plus docetaxel markedly down-regulated two genes, HEC and DEEPEST, required for passage through G(2)-M. Thus, anti-HER2 antibody preferentially affects genes contributing to cell cycle progression and cell growth/maintenance, in part through the PI3K-AKT signaling. Transcriptional regulation by anti-HER2 antibody through PI3K-AKT pathway may potentiate the growth inhibitory activity of docetaxel by affecting cell cycle progression.
A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of a prolongation or process extending from a cell, e.g. a flagellum or axon.
A cell cycle process comprising the steps by which the nucleus of a eukaryotic cell divides; the process involves condensation of chromosomal DNA into a highly compacted form. Canonically, mitosis produces two daughter nuclei whose chromosome complement is identical to that of the mother cell.
A series of molecular signals in which a cell uses a phosphatidylinositol-mediated signaling to convert a signal into a response. Phosphatidylinositols include phosphatidylinositol (PtdIns) and its phosphorylated derivatives.
The molecular mechanisms by which the anti-HER2 antibodies trastuzumab and its murine equivalent 4D5 inhibit tumor growth and potentiate chemotherapy are not fully understood. Inhibition of signaling through the phosphatidylinositol 3-kinase (PI3K)-AKT pathway may be particularly important. Treatment of breast cancer cells that overexpress HER2 with trastuzumab inhibited HER2-HER3 association, decreased PDK1 activity, reduced Thr-308 and Ser-473 phosphorylation of AKT, and reduced AKT enzymatic activity. To place the role of PI3K-AKT in perspective, gene expression was studied by using Affymetrix microarrays and real time reverse transcription-PCR. Sixteen genes were consistently down-regulated 2.0-4.9-fold in two antibody-treated breast cancer cell lines. Fourteen of the 16 genes were involved in three major functional areas as follows: 7 in cell cycle regulation, particularly of the G(2)-M; 5 in DNA repair/replication; and 2 in modifying chromatin structure. Of the 16 antibody-regulated genes, 64% had roles in cell growth/maintenance and 52% contributed to the cell cycle. Direct inhibition of PI3K with an inhibitor markedly reduced expression of 14 genes that were also affected by the antibody. Constitutive activation of AKT1 blocked the effect of the anti-HER2 antibody on cell cycle arrest and on eight differentially expressed genes. The antibody enhanced docetaxel-induced growth inhibition but did not increase the fraction of apoptotic cells induced with docetaxel alone. In contrast, the antibody plus docetaxel markedly down-regulated two genes, HEC and DEEPEST, required for passage through G(2)-M. Thus, anti-HER2 antibody preferentially affects genes contributing to cell cycle progression and cell growth/maintenance, in part through the PI3K-AKT signaling. Transcriptional regulation by anti-HER2 antibody through PI3K-AKT pathway may potentiate the growth inhibitory activity of docetaxel by affecting cell cycle progression.
The centrosome, also known as the microtubule organizing center of the cell, is a membrane-less organelle composed of a pair of barrel-shaped centrioles surrounded by electron-dense pericentriolar material. The centrosome progresses through the centrosome cycle in step with the cell cycle such that centrosomes are duplicated in time to serve as the spindle poles during mitosis and that each resultant daughter cell contains a single centrosome. Regulation of the centrosome cycle with relation to the cell cycle is an essential process to maintain the ratio of one centrosome per new daughter cell. Numerous mitosis-specific kinases have been implicated in this regulation, and phosphorlyation plays an important role in coordinating the centrosome and cell cycles. Centrosome amplification can occur when the cycles are uncoupled, and this amplification is associated with cancer and with an increase in the levels of chromosomal instability. The aurora kinases A, B, and C are serine/threonine kinases that are active during mitosis. Aurora A is associated with centrosomes, being localized at the centrosome just prior to the onset of mitosis and for the duration of mitosis. Overexpression of aurora A leads to centrosome amplification and cellular transformation. The activity of aurora A is regulated by phosphorlyation and proteasomal degradation.
The centrosome, also known as the microtubule organizing center of the cell, is a membrane-less organelle composed of a pair of barrel-shaped centrioles surrounded by electron-dense pericentriolar material. The centrosome progresses through the centrosome cycle in step with the cell cycle such that centrosomes are duplicated in time to serve as the spindle poles during mitosis and that each resultant daughter cell contains a single centrosome. Regulation of the centrosome cycle with relation to the cell cycle is an essential process to maintain the ratio of one centrosome per new daughter cell. Numerous mitosis-specific kinases have been implicated in this regulation, and phosphorlyation plays an important role in coordinating the centrosome and cell cycles. Centrosome amplification can occur when the cycles are uncoupled, and this amplification is associated with cancer and with an increase in the levels of chromosomal instability. The aurora kinases A, B, and C are serine/threonine kinases that are active during mitosis. Aurora A is associated with centrosomes, being localized at the centrosome just prior to the onset of mitosis and for the duration of mitosis. Overexpression of aurora A leads to centrosome amplification and cellular transformation. The activity of aurora A is regulated by phosphorlyation and proteasomal degradation.
J. Biol. Chem. 272, 13766-13771 (1997)[PubMed:9153231]
Mutations in Aurora of Drosophila and related Saccharomyces cerevisiae Ipl1 kinase are known to cause abnormal chromosome segregation. We have isolated a cDNA encoding a novel human protein kinase of 402 amino acids with a predicted molecular mass of 45.9 kDa, which shares high amino acid identities with the Aurora/Ipl1 protein kinase family; hence the cDNA is designated as aik (aurora/IPL1-related kinase). Amino acid sequence of C-terminal kinase domain of Aik shares 86, 86, 72, 59, and 49% identity with those of Xenopus XLP46APK and XLP46BPK, mouse STK-1, Aurora of Drosophila, and yeast Ipl1, respectively, whereas N-terminal domain of Aik shares high homology only with those of XLP46APK and XLP46BPK. Northern and Western blotting analyses revealed that Aik is expressed highly in testis and various proliferating cells including HeLa cells. In HeLa cells, the endogenous levels of aik mRNA and protein contents are tightly regulated during cell cycle progression. Both of these levels are low in G1/S, accumulate during G2/M, and reduce rapidly after mitosis. Its protein kinase activity is also enhanced at mitosis as inferred by exogenous casein phosphorylation. Immunofluorescence studies using a specific antibody have shown that Aik is localized to the spindle pole during mitosis, especially from prophase through anaphase. These results strongly suggest that Aik is a novel member of a protein kinase family possibly involved in a centrosome function(s) such as chromosome segregation or spindle formation.
The centrosome, also known as the microtubule organizing center of the cell, is a membrane-less organelle composed of a pair of barrel-shaped centrioles surrounded by electron-dense pericentriolar material. The centrosome progresses through the centrosome cycle in step with the cell cycle such that centrosomes are duplicated in time to serve as the spindle poles during mitosis and that each resultant daughter cell contains a single centrosome. Regulation of the centrosome cycle with relation to the cell cycle is an essential process to maintain the ratio of one centrosome per new daughter cell. Numerous mitosis-specific kinases have been implicated in this regulation, and phosphorlyation plays an important role in coordinating the centrosome and cell cycles. Centrosome amplification can occur when the cycles are uncoupled, and this amplification is associated with cancer and with an increase in the levels of chromosomal instability. The aurora kinases A, B, and C are serine/threonine kinases that are active during mitosis. Aurora A is associated with centrosomes, being localized at the centrosome just prior to the onset of mitosis and for the duration of mitosis. Overexpression of aurora A leads to centrosome amplification and cellular transformation. The activity of aurora A is regulated by phosphorlyation and proteasomal degradation.
Aurora-A, a mitotic serine/threonine kinase with oncogene characteristics, has recently drawn intense attention because of its association with the development of human cancers and its relationship with mitotic progression. Using the gene expression profiles of Aurora-A as a template to search for and compare transcriptome expression profiles in publicly accessible microarray data sets, we identified HURP (encodes hepatoma upregulated protein) as one of the best Aurora-A-correlated genes. Empirical validation indicates that HURP has several characteristics in common with Aurora-A. These two genes have similar expression patterns in hepatocellular carcinoma, liver regeneration after partial hepatectomy, and cell cycle progression and across a variety of tissues and cell lines. Moreover, Aurora-A phosphorylated HURP in vitro and in vivo. Ectopic expression of either the catalytically inactive form of Aurora-A or the HURP-4P mutant, in which the Aurora-A phosphorylation sites were replaced with Ala, resulted in HURP instability and complex disassembly. In addition, HURP-wild-type stable transfectants were capable of growing in low-serum environments whereas HURP-4P grew poorly under low-serum conditions and failed to proliferate. These studies together support the view that the ability to integrate evidence derived from microarray studies into biochemical analyses may ultimately augment our predictive power when analyzing the potential role of poorly characterized proteins. While this combined approach was simply an initial attempt to answer a range of complex biological questions, our findings do suggest that HURP is a potential oncogenic target of Aurora-A.
A process that is carried out at the cellular level which results in the assembly, arrangement of constituent parts, or disassembly of the spindle, the array of microtubules and associated molecules that forms between opposite poles of a eukaryotic cell during DNA segregation and serves to move the duplicated chromosomes apart.
The molecular mechanisms by which the anti-HER2 antibodies trastuzumab and its murine equivalent 4D5 inhibit tumor growth and potentiate chemotherapy are not fully understood. Inhibition of signaling through the phosphatidylinositol 3-kinase (PI3K)-AKT pathway may be particularly important. Treatment of breast cancer cells that overexpress HER2 with trastuzumab inhibited HER2-HER3 association, decreased PDK1 activity, reduced Thr-308 and Ser-473 phosphorylation of AKT, and reduced AKT enzymatic activity. To place the role of PI3K-AKT in perspective, gene expression was studied by using Affymetrix microarrays and real time reverse transcription-PCR. Sixteen genes were consistently down-regulated 2.0-4.9-fold in two antibody-treated breast cancer cell lines. Fourteen of the 16 genes were involved in three major functional areas as follows: 7 in cell cycle regulation, particularly of the G(2)-M; 5 in DNA repair/replication; and 2 in modifying chromatin structure. Of the 16 antibody-regulated genes, 64% had roles in cell growth/maintenance and 52% contributed to the cell cycle. Direct inhibition of PI3K with an inhibitor markedly reduced expression of 14 genes that were also affected by the antibody. Constitutive activation of AKT1 blocked the effect of the anti-HER2 antibody on cell cycle arrest and on eight differentially expressed genes. The antibody enhanced docetaxel-induced growth inhibition but did not increase the fraction of apoptotic cells induced with docetaxel alone. In contrast, the antibody plus docetaxel markedly down-regulated two genes, HEC and DEEPEST, required for passage through G(2)-M. Thus, anti-HER2 antibody preferentially affects genes contributing to cell cycle progression and cell growth/maintenance, in part through the PI3K-AKT signaling. Transcriptional regulation by anti-HER2 antibody through PI3K-AKT pathway may potentiate the growth inhibitory activity of docetaxel by affecting cell cycle progression.
A novel series of 5-aminopyrimidinyl quinazolines has been developed from anilino-quinazoline 1, which was identified in a high throughput screen for Aurora A. Introduction of the pyrimidine ring and optimisation of the substituents both on this ring and at the C7 position of the quinazoline led to the discovery of compounds that are highly specific Aurora kinase inhibitors. Co-crystallisation of one of these inhibitors with a fragment of Aurora A shows the importance of the benzamido group in achieving selectivity.
The two major Aurora kinases carry out critical functions at distinct mitotic stages. Selective inhibitors of these kinases, as well as pan-Aurora inhibitors, show antitumor efficacy and are now under clinical investigation. However, the ATP-binding sites of Aurora A and Aurora B are virtually identical, and the structural basis for selective inhibition has therefore not been clear. We report here a class of bisanilinopyrimidine Aurora A inhibitors with excellent selectivity for Aurora A over Aurora B, both in enzymatic assays and in cellular phenotypic assays. Crystal structures of two of the inhibitors in complex with Aurora A implicate a single amino acid difference in Aurora B as responsible for poor inhibitory activity against this enzyme. Mutation of this residue in Aurora B (E161T) or Aurora A (T217E) is sufficient to swap the inhibition profile, suggesting that this difference might be exploited more generally to achieve high selectivity for Aurora A.
Aurora kinases have emerged as attractive targets for the design of anticancer drugs. Through structure-based virtual screening, novel pyrazole hit 8a was identified as Aurora kinase A inhibitor (IC(50) = 15.1 microM). X-ray cocrystal structure of 8a in complex with Aurora A protein revealed the C-4 position ethyl carboxylate side chain as a possible modification site for improving the potency. On the basis of this insight, bioisosteric replacement of the ester with amide linkage and changing the ethyl substituent to hydrophobic 3-acetamidophenyl ring led to the identification of 12w with a approximately 450-fold improved Aurora kinase A inhibition potency (IC(50) = 33 nM), compared to 8a. Compound 12w showed selective inhibition of Aurora A kinase over Aurora B/C, which might be due to the presence of a unique H-bond interaction between the 3-acetamido group and the Aurora A nonconserved Thr217 residue, which in Aurora B/C is Glu and found to sterically clash with the 3-acetamido group in modeling studies.
Aurora-2 is a key member of a closely related subgroup of serine/threonine kinases that plays important roles in the completion of essential mitotic events. Aurora-2 is oncogenic and amplified in various human cancers and could be an important therapeutic target for inhibitory molecules that would disrupt the cell cycle and block proliferation. We report the first crystal structure of Aurora-2 kinase in complex with adenosine. Analysis of residues in the active site suggests differences with structurally and biologically related protein kinases. The activation loop, which contains residues specific to the Aurora family of kinases, has a unique conformation. These results provide valuable insight into the design of selective and highly potent ATP-competitive inhibitors of the Aurora kinases.
Activation of CDK1, appears to be an upstream event of AURKA activation. Phosphatase inhibitor-2 (PPP1R2) and TPX2 act also as activators. Inactivated by the G2 checkpoint. Inhibited by GADD45A and p53/TP53, and through dephosphorylation by protein phosphatase type 1 (PP1). MLN8054 is also a potent and selective inhibitor. Activated during the early phase of cilia disassembly in the presence of PIFO.
Aurora2 is a cell cycle regulated serine/threonine protein kinase which is overexpressed in many tumor cell lines. We demonstrate that Aurora2 is regulated by phosphorylation in a cell cycle dependent manner. This phosphorylation occurs on a conserved residue, Threonine 288, within the activation loop of the catalytic domain of the kinase and results in a significant increase in the enzymatic activity. Threonine 288 resides within a consensus motif for the cAMP dependent kinase and can be phosphorylated by PKA in vitro. The protein phosphatase 1 is shown to dephosphorylate this site in vitro, and in vivo the phosphorylation of T288 is induced by okadaic acid treatment. Furthermore, we show that the Aurora2 kinase is regulated by proteasome dependent degradation and that Aurora2 phosphorylated on T288 may be targeted for degradation during mitosis. Our experiments suggest that phosphorylation of T288 is important for regulation of the Aurora2 kinase both for its activity and its stability.
Increased Aurora A expression occurs in a variety of human cancers and induces chromosomal abnormalities during mitosis associated with tumor initiation and progression. MLN8054 is a selective small-molecule Aurora A kinase inhibitor that has entered Phase I clinical trials for advanced solid tumors. MLN8054 inhibits recombinant Aurora A kinase activity in vitro and is selective for Aurora A over the family member Aurora B in cultured cells. MLN8054 treatment results in G(2)/M accumulation and spindle defects and inhibits proliferation in multiple cultured human tumor cells lines. Growth of human tumor xenografts in nude mice was dramatically inhibited after oral administration of MLN8054 at well tolerated doses. Moreover, the tumor growth inhibition was sustained after discontinuing MLN8054 treatment. In human tumor xenografts, MLN8054 induced mitotic accumulation and apoptosis, phenotypes consistent with inhibition of Aurora A. MLN8054 is a selective inhibitor of Aurora A kinase that robustly inhibits growth of human tumor xenografts and represents an attractive modality for therapeutic intervention of human cancers.
Various mitotic events are controlled by Cdc2-cyclin B and other mitotic kinases. Aurora/Ipl1-related mitotic kinases were proved to play key roles in mitotic progression in diverse lower organisms. Aurora-A is a mammalian counterpart of aurora/Ipl1-related kinases and is thought to be a potential oncogene. However, the regulation of aurora-A activation and the commitment of aurora-A in the progression of G2-M phase are largely unknown in mammalian cells.
Centrosome amplification can occur when the cycles are uncoupled, and this amplification is associated with cancer and with an increase in the levels of chromosomal instability.
CuratedUniProtKB
Caution
Authors initially considered AURKA/STK6 and STK15 as 2 different proteins (PubMed9771714). It is clear that they are the same protein.
The centrosomes are thought to maintain genomic stability through the establishment of bipolar spindles during cell division, ensuring equal segregation of replicated chromosomes to two daughter cells. Deregulated duplication and distribution of centrosomes have been implicated in chromosome segregation abnormalities, leading to aneuploidy seen in many cancer cell types. Here, we report that STK15 (also known as BTAK and aurora2), encoding a centrosome-associated kinase, is amplified and overexpressed in multiple human tumour cell types, and is involved in the induction of centrosome duplication-distribution abnormalities and aneuploidy in mammalian cells. STK15 amplification has been previously detected in breast tumour cell lines and in colon tumours; here, we report its amplification in approximately 12% of primary breast tumours, as well as in breast, ovarian, colon, prostate, neuroblastoma and cervical cancer cell lines. Additionally, high expression of STK15 mRNA was detected in tumour cell lines without evidence of gene amplification. Ectopic expression of STK15 in mouse NIH 3T3 cells led to the appearance of abnormal centrosome number (amplification) and transformation in vitro. Finally, overexpression of STK15 in near diploid human breast epithelial cells revealed similar centrosome abnormality, as well as induction of aneuploidy. These findings suggest that STK15 is a critical kinase-encoding gene, whose overexpression leads to centrosome amplification, chromosomal instability and transformation in mammalian cells.
Protein involved in the complex series of events by which the cell duplicates its contents and divides into two. The eukaryotic cell cycle can be divided in four phases termed G1 (first gap period), S (synthesis, phase during which the DNA is replicated), G2 (second gap period) and M (mitosis). The prokaryotic cell cycle typically involves a period of growth followed by DNA replication, partition of chromosomes, formation of septum and division into two similar or identical daughter cells.
Protein involved in the separation of one cell into two daughter cells. In eukaryotic cells, cell division includes the nuclear division (mitosis) and the subsequent cytoplasmic division (cytokinesis).
Protein which is involved in the formation, organization, maintenance and degradation of the cilium, a cell surface projection found at the surface of a large proportion of eukaryotic. Their most prominent structural component is the axoneme which consists of nine doublet microtubules, with all motile cilia - except those at the embryonic node - containing an additional central pair of microtubules.
Protein involved in mitosis, the nuclear division in eukaryotic cells involving the exact duplication and separation of the chromosome threads so that each daughter nucleus carries a chromosome complement identical to that of the parent nucleus. Mitosis is divided into four substages: prophase, metaphase, anaphase and telophase.
Protein which catalyzes the phosphorylation of serine or threonine residues on target proteins by using ATP as phosphate donor. Such phosphorylation may cause changes in the function of the target protein. Protein kinases share a conserved catalytic core common to both serine/ threonine and tyrosine protein kinases.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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