AKT2 is one of 3 closely related serine/threonine-protein kinases (AKT1, AKT2 and AKT3) called the AKT kinase, and which regulate many processes including metabolism, proliferation, cell survival, growth and angiogenesis. This is mediated through serine and/or threonine phosphorylation of a range of downstream substrates. Over 100 substrate candidates have been reported so far, but for most of them, no isoform specificity has been reported. AKT is responsible of the regulation of glucose uptake by mediating insulin-induced translocation of the SLC2A4/GLUT4 glucose transporter to the cell surface. Phosphorylation of PTPN1 at 'Ser-50' negatively modulates its phosphatase activity preventing dephosphorylation of the insulin receptor and the attenuation of insulin signaling. Phosphorylation of TBC1D4 triggers the binding of this effector to inhibitory 14-3-3 proteins, which is required for insulin-stimulated glucose transport. AKT regulates also the storage of glucose in the form of glycogen by phosphorylating GSK3A at 'Ser-21' and GSK3B at 'Ser-9', resulting in inhibition of its kinase activity. Phosphorylation of GSK3 isoforms by AKT is also thought to be one mechanism by which cell proliferation is driven. AKT regulates also cell survival via the phosphorylation of MAP3K5 (apoptosis signal-related kinase). Phosphorylation of 'Ser-83' decreases MAP3K5 kinase activity stimulated by oxidative stress and thereby prevents apoptosis. AKT mediates insulin-stimulated protein synthesis by phosphorylating TSC2 at 'Ser-939' and 'Thr-1462', thereby activating mTORC1 signaling and leading to both phosphorylation of 4E-BP1 and in activation of RPS6KB1. AKT is involved in the phosphorylation of members of the FOXO factors (Forkhead family of transcription factors), leading to binding of 14-3-3 proteins and cytoplasmic localization. In particular, FOXO1 is phosphorylated at 'Thr-24', 'Ser-256' and 'Ser-319'. FOXO3 and FOXO4 are phosphorylated on equivalent sites. AKT has an important role in the regulation of NF-kappa-B-dependent gene transcription and positively regulates the activity of CREB1 (cyclic AMP (cAMP)-response element binding protein). The phosphorylation of CREB1 induces the binding of accessory proteins that are necessary for the transcription of pro-survival genes such as BCL2 and MCL1. AKT phosphorylates 'Ser-454' on ATP citrate lyase (ACLY), thereby potentially regulating ACLY activity and fatty acid synthesis. Activates the 3B isoform of cyclic nucleotide phosphodiesterase (PDE3B) via phosphorylation of 'Ser-273', resulting in reduced cyclic AMP levels and inhibition of lipolysis. Phosphorylates PIKFYVE on 'Ser-318', which results in increased PI(3)P-5 activity. The Rho GTPase-activating protein DLC1 is another substrate and its phosphorylation is implicated in the regulation cell proliferation and cell growth. AKT plays a role as key modulator of the AKT-mTOR signaling pathway controlling the tempo of the process of newborn neurons integration during adult neurogenesis, including correct neuron positioning, dendritic development and synapse formation. Signals downstream of phosphatidylinositol 3-kinase (PI(3)K) to mediate the effects of various growth factors such as platelet-derived growth factor (PDGF), epidermal growth factor (EGF), insulin and insulin-like growth factor I (IGF-I). AKT mediates the antiapoptotic effects of IGF-I. Essential for the SPATA13-mediated regulation of cell migration and adhesion assembly and disassembly. May be involved in the regulation of the placental development.
Akt1 and Akt2 are the major isoforms of Akt expressed in muscle cells and muscle tissue. We have performed siRNA silencing of Akt1 and Akt2 in C2 myoblasts to characterize their specific implication in muscle differentiation. Whereas silencing Akt2, and not Akt1, inhibited cell cycle exit and myoblast differentiation, Akt2 overexpression led to an increased proportion of differentiated myoblasts. In addition, we demonstrate that Akt2 is required for myogenic conversion induced by MyoD overexpression in fibroblasts. We show Akt2, but not Akt1, binds Prohibitin2/Repressor of Estrogen Activator, PHB2/REA, a protein recently implicated in transcriptionnal repression of myogenesis. Co-immunoprecipitation experiments on endogenous proteins showed the Akt2-REA complex does not contain Prohibitin1. We have analyzed expression and localization of PHB2/REA during proliferation and differentiation of mouse and human myoblasts. PHB2/REA shows punctated nuclear staining which partially co-localizes with Akt2 in differentiated myotubes and PHB2 levels decrease at the onset of myogenic differentiation concomitant with an increase in Akt2. There appears to be an inverse correlation between Akt2 and PHB2 protein levels where cells silenced for Akt2 expression show increased level of PHB2/REA and overexpression of Akt2 resulted in decreased Prohibitin2/REA. Taken together, these results, along with our previous observations, clearly show that Akt2 and not Akt1 plays a major and early role in cell cycle exit and myogenic differentiation and this function involves its specific interaction with PHB2/REA.
One of the few specific substrates of AKT2 identified recently is PITX2. Phosphorylation of PITX2 impairs its association with the CCND1 mRNA-stabilizing complex thus shortening the half-life of CCND1. AKT2 seems also to be the principal isoform responsible of the regulation of glucose uptake. AKT2 is also specifically involved in skeletal muscle differentiation. Down-regulation by RNA interference reduces the expression of the phosphorylated form of BAD, resulting in the induction of caspase-dependent apoptosis. Phosphorylates CLK2 on 'Thr-343'.
Akt1 and Akt2 are the major isoforms of Akt expressed in muscle cells and muscle tissue. We have performed siRNA silencing of Akt1 and Akt2 in C2 myoblasts to characterize their specific implication in muscle differentiation. Whereas silencing Akt2, and not Akt1, inhibited cell cycle exit and myoblast differentiation, Akt2 overexpression led to an increased proportion of differentiated myoblasts. In addition, we demonstrate that Akt2 is required for myogenic conversion induced by MyoD overexpression in fibroblasts. We show Akt2, but not Akt1, binds Prohibitin2/Repressor of Estrogen Activator, PHB2/REA, a protein recently implicated in transcriptionnal repression of myogenesis. Co-immunoprecipitation experiments on endogenous proteins showed the Akt2-REA complex does not contain Prohibitin1. We have analyzed expression and localization of PHB2/REA during proliferation and differentiation of mouse and human myoblasts. PHB2/REA shows punctated nuclear staining which partially co-localizes with Akt2 in differentiated myotubes and PHB2 levels decrease at the onset of myogenic differentiation concomitant with an increase in Akt2. There appears to be an inverse correlation between Akt2 and PHB2 protein levels where cells silenced for Akt2 expression show increased level of PHB2/REA and overexpression of Akt2 resulted in decreased Prohibitin2/REA. Taken together, these results, along with our previous observations, clearly show that Akt2 and not Akt1 plays a major and early role in cell cycle exit and myogenic differentiation and this function involves its specific interaction with PHB2/REA.
AKT/PKB is a phosphoinositide-dependent serine/threonine protein kinase that plays a critical role in the signal transduction of receptors. It also serves as an oncogene in the tumorigenesis of cancer cells when aberrantly activated by genetic lesions of the PTEN tumor suppressor, phosphatidylinositol 3-kinase, and receptor tyrosine kinase overexpression. Here we have characterized and compared kinetic mechanisms of the three AKT isoforms. Initial velocity studies revealed that all AKT isozymes follow the sequential kinetic mechanism by which an enzyme-substrate ternary complex forms before the product release. The empirically derived kinetic parameters are apparently different among the isoforms. AKT2 showed the highest Km value for ATP, and AKT3 showed the highest kcat value. The patterns of product inhibition of AKT1, AKT2, and AKT3 by ADP were all consistent with an ordered substrate addition mechanism with ATP binding to the enzymes prior to the peptide substrate. Further analysis of steady state kinetics of AKT1 in the presence of dead-end inhibitors supported the finding and suggested that the AKT family of kinases catalyzes reactions via an Ordered Bi Bi sequential mechanism with ATP binding to the enzyme prior to peptide substrate and ADP being released after the phosphopeptide product. These results suggest that ATP is an initiating factor for the catalysis of AKT enzymes and may play a role in the regulation AKT enzyme activity in cells.
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
Akt signaling plays a central role in many biological functions, such as cell proliferation and apoptosis. Because Akt (also known as protein kinase B) resides primarily in the cytosol, it is not known how these signaling molecules are recruited to the plasma membrane and subsequently activated by growth factor stimuli. We found that the protein kinase Akt undergoes lysine-63 chain ubiquitination, which is important for Akt membrane localization and phosphorylation. TRAF6 was found to be a direct E3 ligase for Akt and was essential for Akt ubiquitination, membrane recruitment, and phosphorylation upon growth-factor stimulation. The human cancer-associated Akt mutant displayed an increase in Akt ubiquitination, in turn contributing to the enhancement of Akt membrane localization and phosphorylation. Thus, Akt ubiquitination is an important step for oncogenic Akt activation.
Evidence
2:
Inferred from Physical InteractionHGNC
A number of signaling proteins have been demonstrated to interact with follicle stimulating hormone (FSH) receptor (FSHR), including APPL1, 14-3-3tau and Akt2. To further define the repertoire of proteins involved in FSH-induced signal transduction, several signaling and adapter proteins were examined for the ability to associate with FSHR. This report shows that, in addition to APPL1, FSHR interacts with FOXO1a and APPL2. Moreover, APPL1 and APPL2 associate with one another via the N-terminus of APPL1, presumably via the Bin-Amphiphysin-Rvs (BAR) domain. The interactions between FSHR and APPL2 and between FSHR and FOXO1a evidently are distinct since FOXO1a does not associate with either APPL1 or with APPL2. Though APPL1 and APPL2 show some similarity in primary sequence, APPL1 associates with Akt2, whereas APPL2 does not. This is the first documented difference in function between APPL1 and APPL2. These results suggest that FSHR, APPL1, APPL2, Akt2 and FOXO1a are organized into distinct scaffolding networks in the cell. Accordingly, the spatial organization of signaling and adapter proteins with FSHR likely facilitates and finely regulates the signal transduction induced by FSH.
Evidence
3:
Inferred from Physical InteractionUniProtKB
Migrating cells need to make different actin assemblies at the cell's leading and trailing edges and to maintain physical separation of signals for these assemblies. This asymmetric control of activities represents one important form of cell polarity. There are significant gaps in our understanding of the components involved in generating and maintaining polarity during chemotaxis. Here we characterize a family of complexes (which we term leading edge complexes), scaffolded by hematopoietic protein 1 (Hem-1), that organize the neutrophil's leading edge. The Wiskott-Aldrich syndrome protein family Verprolin-homologous protein (WAVE)2 complex, which mediates activation of actin polymerization by Rac, is only one member of this family. A subset of these leading edge complexes are biochemically separable from the WAVE2 complex and contain a diverse set of potential polarity-regulating proteins. RNA interference-mediated knockdown of Hem-1-containing complexes in neutrophil-like cells: (a) dramatically impairs attractant-induced actin polymerization, polarity, and chemotaxis; (b) substantially weakens Rac activation and phosphatidylinositol-(3,4,5)-tris-phosphate production, disrupting the (phosphatidylinositol-(3,4,5)-tris-phosphate)/Rac/F-actin-mediated feedback circuit that organizes the leading edge; and (c) prevents exclusion of activated myosin from the leading edge, perhaps by misregulating leading edge complexes that contain inhibitors of the Rho-actomyosin pathway. Taken together, these observations show that versatile Hem-1-containing complexes coordinate diverse regulatory signals at the leading edge of polarized neutrophils, including but not confined to those involving WAVE2-dependent actin polymerization.
Evidence
4:
Inferred from Physical InteractionUniProtKB
The serine threonine kinase Akt is a core survival factor that underlies a variety of human diseases. Although regulatory phosphorylation and dephosphorylation have been well documented, the other posttranslational mechanisms that modulate Akt activity remain unclear. We show here that tetratricopeptide repeat domain 3 (TTC3) is an E3 ligase that interacts with Akt. TTC3 contains a canonical RING finger motif, a pair of tetratricopeptide motifs, a putative Akt phosphorylation site, and nuclear localization signals, and is encoded by a gene within the Down syndrome (DS) critical region on chromosome 21. TTC3 is an Akt-specific E3 ligase that binds to phosphorylated Akt and facilitates its ubiquitination and degradation within the nucleus. Moreover, DS cells exhibit elevated TTC3 expression, reduced phosphorylated Akt, and accumulation in the G(2)M phase, which can be reversed by TTC3 siRNA or Myr-Akt. Thus, interaction between TTC3 and Akt may contribute to the clinical symptoms of DS.
Evidence
5:
Inferred from Physical InteractionIntAct
The protein kinase Akt/PKB is stimulated by the phosphorylation of two regulatory residues, Thr 309 of the activation segment and Ser 474 of the hydrophobic motif (HM), that are structurally and functionally conserved within the AGC kinase family. To understand the mechanism of PKB regulation, we determined the crystal structures of activated kinase domains of PKB in complex with a GSK3beta-peptide substrate and an ATP analog. The activated state of the kinase was generated by phosphorylating Thr 309 using PDK1 and mimicking Ser 474 phosphorylation either with the S474D substitution or by replacing the HM of PKB with that of PIFtide, a potent mimic of a phosphorylated HM. Comparison with the inactive PKB structure indicates that the role of Ser 474 phosphorylation is to promote the engagement of the HM with the N-lobe of the kinase domain, promoting a disorder-to-order transition of the alphaC helix. The alphaC helix, by interacting with pThr 309, restructures and orders the activation segment, generating an active kinase conformation. Analysis of the interactions between PKB and the GSK3beta-peptide explains how PKB selects for protein substrates distinct from those of PKA.
Evidence
6:
Inferred from Physical InteractionIntAct
The PI3K/AKT signaling pathway is aberrant in a wide variety of cancers. Downstream effectors of AKT are involved in survival, growth and metabolic-related pathways. In contrast, contradictory data relating to AKT effects on cell motility and invasion, crucial prometastatic processes, have been reported pointing to a potential cell type and isoform type-specific AKT-driven function. By implication, study of AKT signaling should optimally be conducted in an appropriate intracellular environment. Prognosis in soft-tissue sarcoma (STS), the aggressive malignancies of mesenchymal origin, is poor, reflecting our modest ability to control metastasis, an effort hampered by lack of insight into molecular mechanisms driving STS progression and dissemination. We examined the impact of the cancer progression-relevant AKT pathway on the mesenchymal tumor cell internal milieu. We demonstrate that AKT1 activation induces STS cell motility and invasiveness at least partially through a novel interaction with the intermediate filament vimentin (Vim). The binding of AKT (tail region) to Vim (head region) results in Vim Ser39 phosphorylation enhancing the ability of Vim to induce motility and invasion while protecting Vim from caspase-induced proteolysis. Moreover, vimentin phosphorylation was shown to enhance tumor and metastasis growth in vivo. Insights into this mesenchymal-related molecular mechanism may facilitate the development of critically lacking therapeutic options for these devastating malignancies.
Evidence
7:
Inferred from Physical InteractionUniProtKB
AKT2 is a serine/threonine kinase implicated in human ovarian and pancreatic cancers. AKT2 is activated by a variety of growth factors and insulin via phosphatidylinositol 3-kinase (PI3K). However, its normal cellular role is not well understood. To gain insight into the function of AKT2, we performed yeast two-hybrid system to screen for interacting proteins. Using this technique, we identified a novel interactor, designated APPL, which contains a pleckstrin homology (PH) domain, a phosphotyrosine binding (PTB) domain and a leucine zipper, classes of motifs defined in signaling molecules as functional interaction domains with specific targets. The PH domain of APPL shows similarity to those found in GTPase-activating proteins such as oligophrenin-1 and Graf, whereas its PTB domain exhibits homology with CED-6, an adaptor protein that promotes engulfment of apoptotic cells, and IB1, a transactivator of the GLUT2 gene. APPL is highly expressed in skeletal muscle, heart, ovary and pancreas, tissues in which AKT2 mRNA is abundant. APPL interacts with the inactive form of AKT2; moreover, APPL binds to the PI3K catalytic subunit, p110alpha. These data suggest that APPL is an adaptor that may tether inactive AKT2 to p110alpha in the cytoplasm and thereby may expedite recruitment of AKT2 and p110alpha to the cell membrane upon mitogenic stimulation. Furthermore, the APPL gene was mapped to human chromosome 3p14.3-p21.1, where deletions and other rearrangements have often been reported in a variety of tumor types. The identification of APPL may facilitate further analysis of the physiological and oncogenic activities of AKT2.
Evidence
8:
Inferred from Physical InteractionIntAct
HSP90 is a molecular chaperone that associates with numerous substrate proteins called clients. It plays many important roles in human biology and medicine, but determinants of client recognition by HSP90 have remained frustratingly elusive. We systematically and quantitatively surveyed most human kinases, transcription factors, and E3 ligases for interaction with HSP90 and its cochaperone CDC37. Unexpectedly, many more kinases than transcription factors bound HSP90. CDC37 interacted with kinases, but not with transcription factors or E3 ligases. HSP90::kinase interactions varied continuously over a 100-fold range and provided a platform to study client protein recognition. In wild-type clients, HSP90 did not bind particular sequence motifs, but rather associated with intrinsically unstable kinases. Stabilization of the kinase in either its active or inactive conformation with diverse small molecules decreased HSP90 association. Our results establish HSP90 client recognition as a combinatorial process: CDC37 provides recognition of the kinase family, whereas thermodynamic parameters determine client binding within the family.
Kinases of the Akt family are integral and essential components in growth factor signaling pathways activated downstream of the membrane bound phospho-inositol-3 kinase. In light of strong homologies in the primary amino acid sequence, the three Akt kinases were long surmised to play redundant and overlapping roles in insulin signaling across the spectra of cell and tissue types. Over the last 10 years, work using mouse knockout models, cell specific inactivation, and more recently targeted gene inactivation, has brought into question the redundancy within Akt kinase isoforms and instead pointed to isoform specific functions in different cellular events and diseases. Here we concentrate on the differential roles played by Akt1 and Akt2 in a variety of cellular processes and in particular during cancer biogenesis. In this overview, we illustrate that while Akt1 and 2 are often implicated in many aspects of cellular transformation, the two isoforms frequently act in a complementary opposing manner. Furthermore, Akt1 and Akt2 kinases interact differentially with modulating proteins and are necessary in relaying roles during the evolution of cancers from deregulated growth into malignant metastatic killers. These different actions of the two isoforms point to the importance of treatments targeting isoform specific events in the development of effective approaches involving Akt kinases in human disease.
AKT/PKB is a phosphoinositide-dependent serine/threonine protein kinase that plays a critical role in the signal transduction of receptors. It also serves as an oncogene in the tumorigenesis of cancer cells when aberrantly activated by genetic lesions of the PTEN tumor suppressor, phosphatidylinositol 3-kinase, and receptor tyrosine kinase overexpression. Here we have characterized and compared kinetic mechanisms of the three AKT isoforms. Initial velocity studies revealed that all AKT isozymes follow the sequential kinetic mechanism by which an enzyme-substrate ternary complex forms before the product release. The empirically derived kinetic parameters are apparently different among the isoforms. AKT2 showed the highest Km value for ATP, and AKT3 showed the highest kcat value. The patterns of product inhibition of AKT1, AKT2, and AKT3 by ADP were all consistent with an ordered substrate addition mechanism with ATP binding to the enzymes prior to the peptide substrate. Further analysis of steady state kinetics of AKT1 in the presence of dead-end inhibitors supported the finding and suggested that the AKT family of kinases catalyzes reactions via an Ordered Bi Bi sequential mechanism with ATP binding to the enzyme prior to peptide substrate and ADP being released after the phosphopeptide product. These results suggest that ATP is an initiating factor for the catalysis of AKT enzymes and may play a role in the regulation AKT enzyme activity in cells.
A programmed cell death process which begins when a cell receives an internal (e.g. DNA damage) or external signal (e.g. an extracellular death ligand), and proceeds through a series of biochemical events (signaling pathways) which typically lead to rounding-up of the cell, retraction of pseudopodes, reduction of cellular volume (pyknosis), chromatin condensation, nuclear fragmentation (karyorrhexis), plasma membrane blebbing and fragmentation of the cell into apoptotic bodies. The process ends when the cell has died. The process is divided into a signaling pathway phase, and an execution phase, which is triggered by the former.
The directed movement of carbohydrate into, out of or within a cell, or between cells, by means of some agent such as a transporter or pore. Carbohydrates are any of a group of organic compounds based of the general formula Cx(H2O)y.
The covalent alteration of one or more amino acids occurring in proteins, peptides and nascent polypeptides (co-translational, post-translational modifications) occurring at the level of an individual cell. Includes the modification of charged tRNAs that are destined to occur in a protein (pre-translation modification).
Proc. Natl. Acad. Sci. U.S.A. 89, 9267-9271 (1992)[PubMed:1409633]
We isolated cDNA clones containing the entire coding region of the putative oncogene AKT2. Sequence analysis and in vitro translation demonstrated that AKT2 encodes a 56-kDa protein with homology to serine/threonine kinases; moreover, this protein contains a Src homology 2-like domain. AKT2 was shown to be amplified and overexpressed in 2 of 8 ovarian carcinoma cell lines and 2 of 15 primary ovarian tumors. AKT2 was mapped to chromosome region 19q13.1-q13.2 by fluorescence in situ hybridization. In the two ovarian carcinoma cell lines exhibiting amplification of AKT2, the amplified sequences were localized within homogeneously staining regions. We conclude that AKT2 belongs to a distinct subfamily of protein-serine/threonine kinases containing Src homology 2-like domains and that alterations of AKT2 may contribute to the pathogenesis of ovarian carcinomas.
Any process that results in a change in state or activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an insulin stimulus. Insulin is a polypeptide hormone produced by the islets of Langerhans of the pancreas in mammals, and by the homologous organs of other organisms.
Type 2 diabetes is associated with defects in insulin signaling and the resulting abnormal glucose and lipid metabolism. The complexity of insulin signaling cascades is highlighted by the existence of multiple isoforms of target proteins implicated in metabolic and gene-regulatory events. We utilized siRNA to decipher the specific role of predominant insulin receptor substrates and Akt isoforms expressed in human skeletal muscle. Gene silencing revealed specialized roles of insulin signaling cascades to metabolic endpoints. IRS-1 and Akt2 were required for myoblast differentiation and glucose metabolism, whereas IRS-2 and Akt1 were dispensable. A key role of IRS-2 and Akt1 in lipid metabolism was revealed, highlighting reciprocal relationships between metabolic pathways. Unraveling the isoform-specific regulation of glucose and lipid metabolism by key elements along insulin signaling cascades through siRNA-mediated gene silencing in human tissues will facilitate the discovery of novel targets for the treatment of diabetes and related metabolic disorders.
The process in which a relatively unspecialized cell acquires specialized features of an adipocyte, an animal connective tissue cell specialized for the synthesis and storage of fat.
Kinases of the Akt family are integral and essential components in growth factor signaling pathways activated downstream of the membrane bound phospho-inositol-3 kinase. In light of strong homologies in the primary amino acid sequence, the three Akt kinases were long surmised to play redundant and overlapping roles in insulin signaling across the spectra of cell and tissue types. Over the last 10 years, work using mouse knockout models, cell specific inactivation, and more recently targeted gene inactivation, has brought into question the redundancy within Akt kinase isoforms and instead pointed to isoform specific functions in different cellular events and diseases. Here we concentrate on the differential roles played by Akt1 and Akt2 in a variety of cellular processes and in particular during cancer biogenesis. In this overview, we illustrate that while Akt1 and 2 are often implicated in many aspects of cellular transformation, the two isoforms frequently act in a complementary opposing manner. Furthermore, Akt1 and Akt2 kinases interact differentially with modulating proteins and are necessary in relaying roles during the evolution of cancers from deregulated growth into malignant metastatic killers. These different actions of the two isoforms point to the importance of treatments targeting isoform specific events in the development of effective approaches involving Akt kinases in human disease.
The chemical reactions and pathways involving glucose, the aldohexose gluco-hexose. D-glucose is dextrorotatory and is sometimes known as dextrose; it is an important source of energy for living organisms and is found free as well as combined in homo- and hetero-oligosaccharides and polysaccharides.
The chemical reactions and pathways resulting in the formation of glycogen, a polydisperse, highly branched glucan composed of chains of D-glucose residues.
Kinases of the Akt family are integral and essential components in growth factor signaling pathways activated downstream of the membrane bound phospho-inositol-3 kinase. In light of strong homologies in the primary amino acid sequence, the three Akt kinases were long surmised to play redundant and overlapping roles in insulin signaling across the spectra of cell and tissue types. Over the last 10 years, work using mouse knockout models, cell specific inactivation, and more recently targeted gene inactivation, has brought into question the redundancy within Akt kinase isoforms and instead pointed to isoform specific functions in different cellular events and diseases. Here we concentrate on the differential roles played by Akt1 and Akt2 in a variety of cellular processes and in particular during cancer biogenesis. In this overview, we illustrate that while Akt1 and 2 are often implicated in many aspects of cellular transformation, the two isoforms frequently act in a complementary opposing manner. Furthermore, Akt1 and Akt2 kinases interact differentially with modulating proteins and are necessary in relaying roles during the evolution of cancers from deregulated growth into malignant metastatic killers. These different actions of the two isoforms point to the importance of treatments targeting isoform specific events in the development of effective approaches involving Akt kinases in human disease.
Type 2 diabetes is associated with defects in insulin signaling and the resulting abnormal glucose and lipid metabolism. The complexity of insulin signaling cascades is highlighted by the existence of multiple isoforms of target proteins implicated in metabolic and gene-regulatory events. We utilized siRNA to decipher the specific role of predominant insulin receptor substrates and Akt isoforms expressed in human skeletal muscle. Gene silencing revealed specialized roles of insulin signaling cascades to metabolic endpoints. IRS-1 and Akt2 were required for myoblast differentiation and glucose metabolism, whereas IRS-2 and Akt1 were dispensable. A key role of IRS-2 and Akt1 in lipid metabolism was revealed, highlighting reciprocal relationships between metabolic pathways. Unraveling the isoform-specific regulation of glucose and lipid metabolism by key elements along insulin signaling cascades through siRNA-mediated gene silencing in human tissues will facilitate the discovery of novel targets for the treatment of diabetes and related metabolic disorders.
Kinases of the Akt family are integral and essential components in growth factor signaling pathways activated downstream of the membrane bound phospho-inositol-3 kinase. In light of strong homologies in the primary amino acid sequence, the three Akt kinases were long surmised to play redundant and overlapping roles in insulin signaling across the spectra of cell and tissue types. Over the last 10 years, work using mouse knockout models, cell specific inactivation, and more recently targeted gene inactivation, has brought into question the redundancy within Akt kinase isoforms and instead pointed to isoform specific functions in different cellular events and diseases. Here we concentrate on the differential roles played by Akt1 and Akt2 in a variety of cellular processes and in particular during cancer biogenesis. In this overview, we illustrate that while Akt1 and 2 are often implicated in many aspects of cellular transformation, the two isoforms frequently act in a complementary opposing manner. Furthermore, Akt1 and Akt2 kinases interact differentially with modulating proteins and are necessary in relaying roles during the evolution of cancers from deregulated growth into malignant metastatic killers. These different actions of the two isoforms point to the importance of treatments targeting isoform specific events in the development of effective approaches involving Akt kinases in human disease.
Negative regulation of plasma membrane long-chain fatty acid transportdefinition[GO:0010748]
Any process that decreases the rate, frequency or extent of plasma membrane long-chain fatty acid transport. Plasma membrane long-chain fatty acid transport is the directed movement of long-chain fatty acids across the plasma membrane.
Type 2 diabetes is associated with defects in insulin signaling and the resulting abnormal glucose and lipid metabolism. The complexity of insulin signaling cascades is highlighted by the existence of multiple isoforms of target proteins implicated in metabolic and gene-regulatory events. We utilized siRNA to decipher the specific role of predominant insulin receptor substrates and Akt isoforms expressed in human skeletal muscle. Gene silencing revealed specialized roles of insulin signaling cascades to metabolic endpoints. IRS-1 and Akt2 were required for myoblast differentiation and glucose metabolism, whereas IRS-2 and Akt1 were dispensable. A key role of IRS-2 and Akt1 in lipid metabolism was revealed, highlighting reciprocal relationships between metabolic pathways. Unraveling the isoform-specific regulation of glucose and lipid metabolism by key elements along insulin signaling cascades through siRNA-mediated gene silencing in human tissues will facilitate the discovery of novel targets for the treatment of diabetes and related metabolic disorders.
Metastasis, the cardinal feature of malignant tumors, is an important clinical variable in patient prognosis. To understand the basis for metastasis, we systematically selected for highly invasive cells from breast cancer cell lines, MCF7 and MDA-MB-453, with moderate to low invasive ability using Boyden chamber invasion assay. The four-cycle selected invasive lines, named MCF7-I4 and MDA-MB-453-I4, respectively, displayed epithelial-mesenchymal transition (EMT) and dramatically enhanced invasive ability. EMT changes were corroborated with decreased level of E-cadherin and increased vimentin, fibronectin, and beta(1) integrin. Twist, a basic helix-loop-helix transcription factor, and AKT2, a known proto-oncogene, were found to be elevated in the invasive cells compared with the parental. Ectopic expression and knockdown of Twist by short interference RNA resulted in significant increase and reduction, respectively, of AKT2 protein and mRNA expression. Twist bound to E-box elements on AKT2 promoter and enhanced its transcriptional activity. Moreover, silencing AKT2 decreased Twist-promoted migration, invasion, and paclitaxel resistance. Reintroducing AKT2 largely rescued the phenotype resulted from knockdown of Twist in I4 cells, suggesting that AKT2 is a downstream target and functional mediator of Twist. Finally, we observed a 68.8% correlation of elevated Twist and AKT2 expression in late-stage breast cancers as oppose to 13% in early-stage breast cancers. Our study identifies Twist as a positive transcriptional regulator of AKT2 expression, and Twist-AKT2 signaling is involved in promoting invasive ability and survival of breast cancer cells.
Type 2 diabetes is associated with defects in insulin signaling and the resulting abnormal glucose and lipid metabolism. The complexity of insulin signaling cascades is highlighted by the existence of multiple isoforms of target proteins implicated in metabolic and gene-regulatory events. We utilized siRNA to decipher the specific role of predominant insulin receptor substrates and Akt isoforms expressed in human skeletal muscle. Gene silencing revealed specialized roles of insulin signaling cascades to metabolic endpoints. IRS-1 and Akt2 were required for myoblast differentiation and glucose metabolism, whereas IRS-2 and Akt1 were dispensable. A key role of IRS-2 and Akt1 in lipid metabolism was revealed, highlighting reciprocal relationships between metabolic pathways. Unraveling the isoform-specific regulation of glucose and lipid metabolism by key elements along insulin signaling cascades through siRNA-mediated gene silencing in human tissues will facilitate the discovery of novel targets for the treatment of diabetes and related metabolic disorders.
Type 2 diabetes is associated with defects in insulin signaling and the resulting abnormal glucose and lipid metabolism. The complexity of insulin signaling cascades is highlighted by the existence of multiple isoforms of target proteins implicated in metabolic and gene-regulatory events. We utilized siRNA to decipher the specific role of predominant insulin receptor substrates and Akt isoforms expressed in human skeletal muscle. Gene silencing revealed specialized roles of insulin signaling cascades to metabolic endpoints. IRS-1 and Akt2 were required for myoblast differentiation and glucose metabolism, whereas IRS-2 and Akt1 were dispensable. A key role of IRS-2 and Akt1 in lipid metabolism was revealed, highlighting reciprocal relationships between metabolic pathways. Unraveling the isoform-specific regulation of glucose and lipid metabolism by key elements along insulin signaling cascades through siRNA-mediated gene silencing in human tissues will facilitate the discovery of novel targets for the treatment of diabetes and related metabolic disorders.
Any process that increases the rate, frequency or extent of glucose metabolism. Glucose metabolic processes are the chemical reactions and pathways involving glucose, the aldohexose gluco-hexose.
Type 2 diabetes is associated with defects in insulin signaling and the resulting abnormal glucose and lipid metabolism. The complexity of insulin signaling cascades is highlighted by the existence of multiple isoforms of target proteins implicated in metabolic and gene-regulatory events. We utilized siRNA to decipher the specific role of predominant insulin receptor substrates and Akt isoforms expressed in human skeletal muscle. Gene silencing revealed specialized roles of insulin signaling cascades to metabolic endpoints. IRS-1 and Akt2 were required for myoblast differentiation and glucose metabolism, whereas IRS-2 and Akt1 were dispensable. A key role of IRS-2 and Akt1 in lipid metabolism was revealed, highlighting reciprocal relationships between metabolic pathways. Unraveling the isoform-specific regulation of glucose and lipid metabolism by key elements along insulin signaling cascades through siRNA-mediated gene silencing in human tissues will facilitate the discovery of novel targets for the treatment of diabetes and related metabolic disorders.
Type 2 diabetes is associated with defects in insulin signaling and the resulting abnormal glucose and lipid metabolism. The complexity of insulin signaling cascades is highlighted by the existence of multiple isoforms of target proteins implicated in metabolic and gene-regulatory events. We utilized siRNA to decipher the specific role of predominant insulin receptor substrates and Akt isoforms expressed in human skeletal muscle. Gene silencing revealed specialized roles of insulin signaling cascades to metabolic endpoints. IRS-1 and Akt2 were required for myoblast differentiation and glucose metabolism, whereas IRS-2 and Akt1 were dispensable. A key role of IRS-2 and Akt1 in lipid metabolism was revealed, highlighting reciprocal relationships between metabolic pathways. Unraveling the isoform-specific regulation of glucose and lipid metabolism by key elements along insulin signaling cascades through siRNA-mediated gene silencing in human tissues will facilitate the discovery of novel targets for the treatment of diabetes and related metabolic disorders.
Any process that increases the frequency, rate or extent of the process of directing proteins towards a membrane, usually using signals contained within the protein.
Any process that modulates the rate, frequency, or extent of cell cycle arrest, the process in which the cell cycle is halted during one of the normal phases.
Kinases of the Akt family are integral and essential components in growth factor signaling pathways activated downstream of the membrane bound phospho-inositol-3 kinase. In light of strong homologies in the primary amino acid sequence, the three Akt kinases were long surmised to play redundant and overlapping roles in insulin signaling across the spectra of cell and tissue types. Over the last 10 years, work using mouse knockout models, cell specific inactivation, and more recently targeted gene inactivation, has brought into question the redundancy within Akt kinase isoforms and instead pointed to isoform specific functions in different cellular events and diseases. Here we concentrate on the differential roles played by Akt1 and Akt2 in a variety of cellular processes and in particular during cancer biogenesis. In this overview, we illustrate that while Akt1 and 2 are often implicated in many aspects of cellular transformation, the two isoforms frequently act in a complementary opposing manner. Furthermore, Akt1 and Akt2 kinases interact differentially with modulating proteins and are necessary in relaying roles during the evolution of cancers from deregulated growth into malignant metastatic killers. These different actions of the two isoforms point to the importance of treatments targeting isoform specific events in the development of effective approaches involving Akt kinases in human disease.
Kinases of the Akt family are integral and essential components in growth factor signaling pathways activated downstream of the membrane bound phospho-inositol-3 kinase. In light of strong homologies in the primary amino acid sequence, the three Akt kinases were long surmised to play redundant and overlapping roles in insulin signaling across the spectra of cell and tissue types. Over the last 10 years, work using mouse knockout models, cell specific inactivation, and more recently targeted gene inactivation, has brought into question the redundancy within Akt kinase isoforms and instead pointed to isoform specific functions in different cellular events and diseases. Here we concentrate on the differential roles played by Akt1 and Akt2 in a variety of cellular processes and in particular during cancer biogenesis. In this overview, we illustrate that while Akt1 and 2 are often implicated in many aspects of cellular transformation, the two isoforms frequently act in a complementary opposing manner. Furthermore, Akt1 and Akt2 kinases interact differentially with modulating proteins and are necessary in relaying roles during the evolution of cancers from deregulated growth into malignant metastatic killers. These different actions of the two isoforms point to the importance of treatments targeting isoform specific events in the development of effective approaches involving Akt kinases in human disease.
Any process that modulates the frequency, rate or extent of the chemical reactions and pathways resulting in the formation of proteins by the translation of mRNA.
The cellular process in which a signal is conveyed to trigger a change in the activity or state of a cell. Signal transduction begins with reception of a signal (e.g. a ligand binding to a receptor or receptor activation by a stimulus such as light), or for signal transduction in the absence of ligand, signal-withdrawal or the activity of a constitutively active receptor. Signal transduction ends with regulation of a downstream cellular process, e.g. regulation of transcription or regulation of a metabolic process. Signal transduction covers signaling from receptors located on the surface of the cell and signaling via molecules located within the cell. For signaling between cells, signal transduction is restricted to events at and within the receiving cell.
Kinases of the Akt family are integral and essential components in growth factor signaling pathways activated downstream of the membrane bound phospho-inositol-3 kinase. In light of strong homologies in the primary amino acid sequence, the three Akt kinases were long surmised to play redundant and overlapping roles in insulin signaling across the spectra of cell and tissue types. Over the last 10 years, work using mouse knockout models, cell specific inactivation, and more recently targeted gene inactivation, has brought into question the redundancy within Akt kinase isoforms and instead pointed to isoform specific functions in different cellular events and diseases. Here we concentrate on the differential roles played by Akt1 and Akt2 in a variety of cellular processes and in particular during cancer biogenesis. In this overview, we illustrate that while Akt1 and 2 are often implicated in many aspects of cellular transformation, the two isoforms frequently act in a complementary opposing manner. Furthermore, Akt1 and Akt2 kinases interact differentially with modulating proteins and are necessary in relaying roles during the evolution of cancers from deregulated growth into malignant metastatic killers. These different actions of the two isoforms point to the importance of treatments targeting isoform specific events in the development of effective approaches involving Akt kinases in human disease.
This protein acts as an enzyme. It is known to catalyze the following reaction
EC 2.7.11.1: ATP + a protein ⇄ ADP + a phosphoprotein.
CuratedUniProtKB
It is regulated in the following manner
Two specific sites, one in the kinase domain (Thr-309) and the other in the C-terminal regulatory region (Ser-474), need to be phosphorylated for its full activation. Aminofurazans are potent AKT2 inhibitors.
AKT inhibitors containing an imidazopyridine aminofurazan scaffold have been optimized. We have previously disclosed identification of the AKT inhibitor GSK690693, which has been evaluated in clinical trials in cancer patients. Herein we describe recent efforts focusing on investigating a distinct region of this scaffold that have afforded compounds (30 and 32) with comparable activity profiles to that of GSK690693.
Overexpression of AKT has an antiapoptotic effect in many cell types, and expression of dominant negative AKT blocks the ability of a variety of growth factors to promote survival. Therefore, inhibitors of AKT kinase activity might be useful as monotherapy for the treatment of tumors with activated AKT. Herein, we describe our lead optimization studies culminating in the discovery of compound 3g (GSK690693). Compound 3g is a novel ATP competitive, pan-AKT kinase inhibitor with IC 50 values of 2, 13, and 9 nM against AKT1, 2, and 3, respectively. An X-ray cocrystal structure was solved with 3g and the kinase domain of AKT2, confirming that 3g bound in the ATP binding pocket. Compound 3g potently inhibits intracellular AKT activity as measured by the inhibition of the phosphorylation levels of GSK3beta. Intraperitoneal administration of 3g in immunocompromised mice results in the inhibition of GSK3beta phosphorylation and tumor growth in human breast carcinoma (BT474) xenografts.
In light of strong homologies in the primary amino acid sequence, the 3 AKT kinases were long surmised to play redundant and overlapping roles. More recent studies has brought into question the redundancy within AKT kinase isoforms and instead pointed to isoform specific functions in different cellular events and diseases. AKT1 is more specifically involved in cellular survival pathways, by inhibiting apoptotic processes; whereas AKT2 is more specific for the insulin receptor signaling pathway. Moreover, while AKT1 and AKT2 are often implicated in many aspects of cellular transformation, the 2 isoforms act in a complementary opposing manner. The role of AKT3 is less clear, though it appears to be predominantly expressed in brain.
CuratedUniProtKB
Biophysicochemical properties
Kinetic
parameters
KM
564 uM for ATP (for recombinant myristoylated AKT2 expressed and immunoprecipitated from Rat-1 cells)
KM
2.3 uM for peptide substrate (for recombinant myristoylated AKT2 expressed and immunoprecipitated from Rat-1 cells)
KM
358.4 uM for ATP (for purified and in vitro activated AKT2)
KM
3.4 uM for peptide substrate (for purified and in vitro activated AKT2)
Protein involved in apoptotic programmed cell death. Apoptosis is characterized by cell morphological changes, including blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation and chromosomal DNA fragmentation, and eventually death. Unlike necrosis, apoptosis produces cell fragments, called apoptotic bodies, that phagocytic cells are able to engulf and quickly remove before the contents of the cell can spill out onto surrounding cells and cause damage. In general, apoptosis confers advantages during an organism's life cycle.
Protein participating in biochemical reactions in which carbohydrates are involved. Carbohydrate is a general term for sugars and related compounds with the general formula Cn(H2O)n. The smallest are monosaccharides (e.g. glucose); polysaccharides (e.g. starch, cellulose, glycogen) can be large and vary in length.
Protein involved in the synthesis of glycogen, a branched polymer of D-glucose (mostly -(1-4) linked, but with some -(1-6) linked residues at branch points). Glycogen is the major short term storage polymer of animal cells and is particularly abundant in liver and to a lesser extent in muscles.
Protein involved in the biochemical reactions with glycogen, a branched polymer of D-glucose (mostly -(1-4) linked, but with some - (1-6) linked residues at branch points). Glycogen is the major short term storage polymer of animal cells and is particularly abundant in liver and to a lesser extent in muscles.
Protein involved in the transport of a molecule (metabolite, protein, etc), a ion or an electron across cell membranes, inside the cell or in a tissue fluid.
Protein involved in development, the process whereby a multicellular organism develops from its early immature forms, e.g., zygote, larva, embryo, into an adult.
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.
My favorites 
My labels 
Login
