May function as a tRNA-specific ribonuclease that abolishes protein synthesis by specifically hydrolyzing cellular tRNAs. Binds to actin on the surface of endothelial cells; once bound, angiogenin is endocytosed and translocated to the nucleus. Angiogenin induces vascularization of normal and malignant tissues. Angiogenic activity is regulated by interaction with RNH1 in vivo.
J. Biol. Chem. 267, 21982-21986 (1992)[PubMed:1400510]
Angiogenin is a 14.4-kDa human plasma protein with 65% homology to RNase A that retains the key active site residues and three of the four RNase A disulfide bonds. We demonstrate that recombinant angiogenin functions as a cytotoxic tRNA-specific RNase in cell-free lysates and when injected into Xenopus oocytes. Inhibition of protein synthesis by angiogenin correlates with degradation of endogenous oocyte tRNA. Exogenous, radiolabeled tRNA is also hydrolyzed by angiogenin, whereas oocyte rRNA and mRNA are not detectably degraded by angiogenin. Protein synthesis was restored to angiogenin-injected oocytes by injecting the RNase inhibitor RNasin plus total Xenopus or calf liver tRNAs, thereby demonstrating that the tRNA degradation induced by angiogenin was the sole cause of cytotoxicity. A similar tRNA-reversible inhibition of protein synthesis was seen in rabbit reticulocyte lysates. Angiogenin therefore appears to be a specific cellular tRNase, whereas five homologues in the RNase A superfamily lack angiogenin's specificity for tRNA. One of these homologues purified from human eosinophils, eosinophil-derived neurotoxin, nonspecifically degrades oocyte RNA similar to RNase A and is also cytotoxic at very low concentrations.
Human angiogenin (ANG) is a homologue of bovine pancreatic ribonuclease (RNase A) that induces neovascularization. ANG is the only human angiogenic factor that possesses ribonucleolytic activity. To stimulate blood vessel growth, ANG must be transported to the nucleus and must retain its catalytic activity. Like other mammalian homologues of RNase A, ANG forms a femtomolar complex with the cytosolic ribonuclease inhibitor protein (RI). To determine whether RI affects ANG-induced angiogenesis, we created G85R/G86R ANG, which possesses 10(6)-fold lower affinity for RI but retains wild-type ribonucleolytic activity. The neovascularization of rabbit corneas by G85R/G86R ANG was more pronounced and more rapid than by wild-type ANG. These findings provide the first direct evidence that RI serves to regulate the biological activity of ANG in vivo.
Proc. Natl. Acad. Sci. U.S.A. 90, 1217-1221 (1993)[PubMed:7679494]
The 42-kDa angiogenin binding protein isolated previously has been purified to electrophoretic homogeneity. It has been identified as a member of the actin family by peptide mapping and partial amino acid sequencing. The interaction of bovine muscle actin with angiogenin is similar to that of the angiogenin binding protein. Angiogenin induces the polymerization of actin below the critical concentration for spontaneous polymerization. The interaction occurs both in solution and on a poly(vinylidene difluoride) membrane. It is inhibited by excess unlabeled angiogenin and also by platelet factor 4 and protamine, which are known inhibitors of angiogenesis. Two other angiogenic molecules, basic fibroblast growth factor and tumor necrosis factor alpha, bind to 125I-labeled actin and can be crosslinked by a water-soluble carbodiimide. Both actin and an anti-actin antibody inhibit the angiogenic activity of angiogenin in the chicken embryo chorioallantoic membrane assay. The results indicate that the angiogenin binding protein is a cell surface actin and suggest that the reaction between angiogenin and this actin is an essential step in the angiogenesis process induced by angiogenin.
It has been suggested that angiogenin binds to an actin-like molecule present on the surface of endothelial cells. Actin inhibits plasmin activity, but the angiogenin-actin complex is not active. In this report, we found that plasmin inhibits the interaction between angiogenin and actin suggesting a possibility that both angiogenin and plasmin may bind to a similar site on actin. Here we report that chANG, an antiangiogenin peptide that binds to the actin-binding site of angiogenin, inhibits the proteolytic activity of plasmin without any apparent effect on the activities of plasminogen activators and matrix metalloproteases. Its antiplasmin activity is comparable with that of actin. chANG inhibits plasmin activity via its binding to plasmin kringle domains while scrambled chANG does not bind to plasmin. chANG also inhibits the invasion of angiogenin-secreting human fibrosarcoma and colorectal carcinoma cells without effecting migration. Furthermore, chANG blocks angiogenesis induced by fibrosarcoma cells and metastasis of colorectal carcinoma cells to the liver. Therefore, the 11-amino acid peptide chANG has both antiangiogenin and antiplasmin activity, and could be useful in the development of anticancer agents.
Angiogenin is a potent inducer of blood-vessel formation with ribonucleolytic activity. Angiogenin binds to high affinity endothelial cell receptors and with lower affinity to extracellular matrix components. Here we report the effect of copper and zinc on these interactions. There was a 4.3-fold increase in angiogenin binding to calf pulmonary artery endothelial cells in the presence of Cu2+ in vitro. A 3.8-fold increase was observed with Zn2+, whereas Ni2+, Co2+, or Li+ had no effect. Specific angiogenin binding to the lower affinity matrix sites was increased by 2.7- and 1.9-fold in the presence of Cu2+ and Zn2+ respectively. Metal ion affinity chromatography and atomic absorption spectrometry were used to show the direct interaction of angiogenin with copper and zinc ions. Angiogenin bound 2.4 mol of copper per mole of protein. We suggest that copper, a modulator of angiogenesis in vivo, may be involved in the regulation of the biological activity of angiogenin.
J. Cell. Biochem. 76, 452-462 (2000)[PubMed:10649442]
Human angiogenin is translocated to the nucleus of human umbilical vein endothelial cells in a time-dependent manner. Exogenous angiogenin appears in the nucleus in 2 min, reaches saturation in 15 min when 85% of the internalized angiogenin is in the nuclei, and remains associated with the nucleus for at least 4 h. Endothelial cells cultured at low density have a much higher capacity to translocate angiogenin to the nucleus than do those cultured at high density. This observation is consistent with previous findings that both the ability of endothelial cells to proliferate in response to angiogenin and the expression of an angiogenin receptor on the cell surface depend on cell density. Nuclear (125)I-angiogenin is not degraded and is neither spontaneously dissociated nor replaced by unlabeled angiogenin. It is, however, released by deoxyribonuclease I, but not by ribonuclease A, suggesting that angiogenin binds to DNA in the nucleus. These results suggest that in addition to acting as a ribonuclease, angiogenin may play a role in regulating gene expression by direct binding to DNA.
Eur. J. Biochem. 260, 825-832 (1999)[PubMed:10103013]
Human angiogenin is a plasma protein with angiogenic and ribonucleolytic activities. Angiogenin inhibited both DNA replication and proliferation of aortic smooth muscle cells. Binding of 125I-angiogenin to bovine aortic smooth muscle cells at 4 degrees C was specific, saturable, reversible and involved two families of interactions. High-affinity binding sites with an apparent dissociation constant of 0.2 nm bound 1 x 104 molecules per cell grown at a density of 3 x 104.cm-2. Low-affinity binding sites with an apparent dissociation constant of 0.1 micrometer bound 4 x 106 molecules.cell-1. High-affinity binding sites decreased as cell density increased and were not detected at confluence. 125I-angiogenin bound specifically to cells routinely grown in serum-free conditions, indicating that the angiogenin-binding components were cell-derived. Affinity labelling of sparse bovine smooth muscle cells yielded seven major specific complexes of 45, 52, 70, 87, 98, 210 and 250-260 kDa. The same pattern was obtained with human cells. Potential modulators of angiogenesis such as protamine, heparin and the placental ribonuclease inhibitor competed for angiogenin binding to the cells. Together these data suggest that cultured bovine and human aortic smooth muscle cells express specific receptors for human angiogenin.
Interacting selectively and non-covalently with heparin, any member of a group of glycosaminoglycans found mainly as an intracellular component of mast cells and which consist predominantly of alternating alpha-(1->4)-linked D-galactose and N-acetyl-D-glucosamine-6-sulfate residues.
Eur. J. Biochem. 260, 825-832 (1999)[PubMed:10103013]
Human angiogenin is a plasma protein with angiogenic and ribonucleolytic activities. Angiogenin inhibited both DNA replication and proliferation of aortic smooth muscle cells. Binding of 125I-angiogenin to bovine aortic smooth muscle cells at 4 degrees C was specific, saturable, reversible and involved two families of interactions. High-affinity binding sites with an apparent dissociation constant of 0.2 nm bound 1 x 104 molecules per cell grown at a density of 3 x 104.cm-2. Low-affinity binding sites with an apparent dissociation constant of 0.1 micrometer bound 4 x 106 molecules.cell-1. High-affinity binding sites decreased as cell density increased and were not detected at confluence. 125I-angiogenin bound specifically to cells routinely grown in serum-free conditions, indicating that the angiogenin-binding components were cell-derived. Affinity labelling of sparse bovine smooth muscle cells yielded seven major specific complexes of 45, 52, 70, 87, 98, 210 and 250-260 kDa. The same pattern was obtained with human cells. Potential modulators of angiogenesis such as protamine, heparin and the placental ribonuclease inhibitor competed for angiogenin binding to the cells. Together these data suggest that cultured bovine and human aortic smooth muscle cells express specific receptors for human angiogenin.
Catalysis of the endonucleolytic cleavage of RNA to 3'-phosphomononucleotides and 3'-phosphooligonucleotides ending in C-P or U-P with 2',3'-cyclic phosphate intermediates.
Interacting selectively and non-covalently with peptides, any of a group of organic compounds comprising two or more amino acids linked by peptide bonds.
It has been suggested that angiogenin binds to an actin-like molecule present on the surface of endothelial cells. Actin inhibits plasmin activity, but the angiogenin-actin complex is not active. In this report, we found that plasmin inhibits the interaction between angiogenin and actin suggesting a possibility that both angiogenin and plasmin may bind to a similar site on actin. Here we report that chANG, an antiangiogenin peptide that binds to the actin-binding site of angiogenin, inhibits the proteolytic activity of plasmin without any apparent effect on the activities of plasminogen activators and matrix metalloproteases. Its antiplasmin activity is comparable with that of actin. chANG inhibits plasmin activity via its binding to plasmin kringle domains while scrambled chANG does not bind to plasmin. chANG also inhibits the invasion of angiogenin-secreting human fibrosarcoma and colorectal carcinoma cells without effecting migration. Furthermore, chANG blocks angiogenesis induced by fibrosarcoma cells and metastasis of colorectal carcinoma cells to the liver. Therefore, the 11-amino acid peptide chANG has both antiangiogenin and antiplasmin activity, and could be useful in the development of anticancer agents.
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
The importance of specific residues in angiogenin for binding to placental ribonuclease inhibitor (PRI) has been assessed by examining the interaction of angiogenin derivatives with PRI. PRI binds native angiogenin with a Ki value of 7.1 X 10(-16) M [Lee, F. S., Shapiro, R., & Vallee, B. L. (1989) Biochemistry 28, 225-230]. Substitution of a Gln for Lys-40 in angiogenin by site-specific mutagenesis decreases the association rate constant 3-fold and increases the dissociation rate constant 440-fold, resulting in a 1300-fold weaker Ki value. The half-life of the mutant.PRI complex is 3.4 h compared to approximately 60 days for the native angiogenin.PRI complex. The magnitude of the change in Ki value suggests that in the complex, Lys-40 forms a salt bridge or hydrogen bond with an anionic moiety in PRI. Carboxymethylation of His-13 or His-114 with bromoacetate increases the Ki value 15-fold, and oxidation of Trp-89 by means of dimethyl sulfoxide and hydrochloric acid increases it 2.4-fold, suggesting that these residues also form part of the contact region with PRI. The changes in Ki value reflect an increase in the dissociation rate constant. On the other hand, dinitrophenylation of either Lys-50 or Lys-60 with 1-fluoro-2,4-dinitrobenzene does not significantly alter the Ki value, suggesting that these residues are not part of the contact region. These results indicate that PRI inhibition minimally involves the three residues critical for the activity of angiogenin--Lys-40, His-13, and His-114--and to a lesser extent its single tryptophan, Trp-89.
Evidence
2:
Inferred from Physical InteractionUniProtKB
Proc. Natl. Acad. Sci. U.S.A. 84, 2238-2241 (1987)[PubMed:3470787]
Human placental ribonuclease inhibitor (PRI) abolishes both the ribonucleolytic activity of angiogenin toward 28S and 18S rRNA and its angiogenic activity on the chicken embryo chorioallantoic membrane. Treatment of the angiogenin-PRI complex with p-hydroxymercuribenzoate releases enzymatically active angiogenin. Assays measuring competition between angiogenin and bovine pancreatic ribonuclease A for PRI reveal that binding of the inhibitor to angiogenin is extremely tight, with a Ki value well below 0.1 nM. The stability of the angiogenin-PRI complex was assessed by cation-exchange HPLC quantitation of free angiogenin. No significant dissociation was detected after 17 hr at 25 degrees C in the presence of a large excess of bovine ribonuclease, which serves as a scavenger for free inhibitor. The results of these experiments, based on the predictive capacity of the angiogenin/RNase homology, suggest that PRI and related inhibitors may participate in the in vivo regulation of angiogenin and that this might have pharmacologic and/or therapeutic implications.
Evidence
3:
Inferred from Physical InteractionIntAct
Previous single-site mutagenesis studies on the complexes of ribonuclease inhibitor (RI) with angiogenin (Ang) and RNase A suggested that in both cases a substantial fraction of the binding energy is concentrated within one small part of the crystallographically observed interface, involving RI residues 434-438. Such energetic "hot spots" are common in protein-protein complexes, but their physical meaning is generally unclear. Here we have investigated this question by examining the detailed interactions within the RI.ligand hot spots and the extent to which they function independently. The effects of Phe versus Ala substitutions show that the key residue Tyr434 interacts with both ligands primarily through its phenyl ring; for Tyr437, the OH group forms the important contacts with RNase A, whereas the phenyl group interacts with Ang. Kinetic characterization of complexes containing multiple substitutions reveals striking, but distinctive, cooperativity in the interactions of RI with the two ligands. The losses in binding energy for the RNase complex associated with replacements of Tyr434 and Asp435, and Tyr434 and Tyr437, are markedly less than additive (i.e., by 2.4 and 1.3 kcal/mol, respectively). In contrast, the energetic effects of the 434 and 435, and 434 and 437, substitution pairs on binding of Ang are fully additive and 2.5 kcal/mol beyond additive, respectively. Superadditivities (0.9-2.4 kcal/mol) are also observed for several multisite replacements involving these inhibitor residues and two Ang residues, Arg5 and Lys40, from this part of the interface. Consequently, the decreases in binding energy for some triple-variant complexes are as large as 8.5-10.1 kcal/mol (compared to a total DeltaG of -21.0 kcal/mol for the wild-type complex). Potential explanations for these functional couplings, many of which occur over distances of >13 A and are not mediated by direct or triangulated contacts, are proposed. These findings show that the basis for the generation of hot spots can be complex, and that these sites can assume significantly more (as with Ang) or less (as with RNase) importance than indicated from the effects of single-site mutations.
Evidence
4:
Inferred from Physical InteractionIntAct
Angiogenin is an angiogenic factor which is involved in tumorigenesis. However, no particular intracellular protein is known to interact directly with angiogenin. In the present study, we reported the identification of alpha-actinin-2, an actin-crosslinking protein, as a potential angiogenin-interacting partner by yeast two-hybrid screening. This interaction was confirmed by different approaches. First, angiogenin was pulled down together with His-tagged alpha-actinin-2 by Ni(2+)-agarose resins. Second, alpha-actinin-2 was coimmunoprecipitated with angiogenin by anti-angiogenin monoclonal antibody. Third, the in vivo interaction of these two proteins was revealed by fluorescence resonance energy transfer analysis. Since members of alpha-actinin family play pivotal roles in cell proliferation, migration, and invasion, the interaction between alpha-actinin-2 and angiogenin may underline one possible mechanism of angiogenin in angiogenesis. Our finding presents the first evidence of an interaction of a cytosolic protein with angiogenin, which might be a novel interference target for anti-angiogenesis and anti-tumor therapy.
Evidence
5:
Inferred from Physical InteractionIntAct
Angiogenin enhances tumorigenesis. However, the mechanisms of angiogenin-induced angiogenesis and cancer cell proliferation remain elusive. In this study, follistatin was identified as a binding partner of angiogenin by a yeast two-hybrid screen and confirmed by a pull-down experiment. The interaction of fluorescently tagged angiogenin and follistatin was monitored in real time by a laser confocal microscope and shown to localize at the sub-nuclear region of HeLa cells. Additional yeast two-hybrid analysis revealed that domains 2 and 3 of follistatin were the minimal structure requirement for angiogenin binding. These findings provide new clues for further studies on the mechanisms of angiogenin-induced angiogenesis or cancer cell growth.
Interacting selectively and non-covalently with one or more specific sites on a receptor molecule, a macromolecule that undergoes combination with a hormone, neurotransmitter, drug or intracellular messenger to initiate a change in cell function.
Proc. Natl. Acad. Sci. U.S.A. 94, 2204-2209 (1997)[PubMed:9122172]
Angiogenin stimulates both [3H]thymidine incorporation and proliferation of human endothelial cells in sparse cultures. Under these conditions, a 170-kDa cell surface protein can be detected that binds angiogenin specifically. Angiogenin-stimulated cell growth is concentration-dependent and is completely inhibited by an anti-angiogenin monoclonal antibody, but not by a nonimmune control antibody. It is not affected by the nonangiogenic homolog, RNase A, nor by other angiogenic proteins, such as basic fibroblast growth factor and its antibody. Results suggest that under specific conditions, endothelial cells express an angiogenin receptor that may mediate angiogenin-stimulated DNA synthesis and proliferation and play an important role in angiogenin-induced angiogenesis.
Angiogenin, a blood vessel inducing protein isolated from a human tumor cell line, has been found to exhibit ribonucleolytic activity. It catalyzes the cleavage of both 28S and 18S ribosomal RNA as determined by agarose gel electrophoresis. The major products formed with these substrates are 100-500 nucleotides in length. In contrast, angiogenin is inactive toward all of the more conventional substrates of the homologous pancreatic ribonucleases. In particular, it does not produce detectable amounts of acid-soluble fragments from high molecular weight wheat germ RNA, poly(C), or poly(U), nor does it hydrolyze cytidine or uridine cyclic 2',3'-phosphate. The high degree of sequence homology between angiogenin and the pancreatic ribonucleases, which includes all three catalytic residues, His-12, Lys-41, and His-119, has thus identified the chemical nature of a potential angiogenin substrate. These results may bear importantly on the physiological function of angiogenin.
Yeast tRNA is a convenient substrate for the assay of the ribonucleolytic activity of human angiogenin. The optimal pH, [NaCl], and temperature for tRNA cleavage by angiogenin are approximately 6.8, 15-30 mM, and approximately 55 degrees C, respectively, as compared with approximately 8.0, 100-200 mM, and approximately 65 degrees C, respectively, for RNase A. Polyanions and metals both inhibit angiogenin and RNase A but to different extents.
Proc. Natl. Acad. Sci. U.S.A. 85, 5961-5965 (1988)[PubMed:2457905]
Low concentrations of angiogenin activate the inositol-specific phospholipase C of cultured pulmonary artery, umbilical vein, and capillary endothelial cells, promoting a transient increase in the intracellular levels of 1,2-diacylglycerol and inositol trisphosphate. The response is strongly dose dependent with a maximum in the ng/ml concentration range and, for some cell lines, a marked decrease at concentrations greater than 1 ng/ml; e.g., arterial endothelial cells respond weakly to angiogenin concentrations comparable to that in normal human plasma (approximately equal to 400 ng/ml). Chemical modification of the active site of angiogenin or inhibition with placental ribonuclease inhibitor abolishes its activation of endothelial cell phospholipase C; this correlates with the concomitant loss of both intrinsic ribonucleolytic and angiogenic activity. The response to low concentrations of angiogenin is consistent with its potency of inducing vascularization in classical angiogenesis assays. In vivo, endothelial cells are exposed to concentrations of angiogenin higher than that required to elicit a cellular response; it seems likely, therefore, that expression of a surface receptor or some other process must be rate limiting in the cellular response.
Proc. Natl. Acad. Sci. U.S.A. 86, 1573-1577 (1989)[PubMed:2646638]
Angiogenin stimulates capillary and umbilical vein endothelial cell prostacyclin secretion but not that of prostaglandins of the E series. The response was quantitated by radioimmunoassay and by [3H]arachidonate labeling followed by analysis of the secreted prostaglandins. The stimulated secretion lasts for several minutes and is optimal at 2-4 min. The dose-response (peak at 1-10 ng/ml) is similar to that previously observed for activation of endothelial cell phospholipase C. Stimulated secretion was blocked by pretreatment with the inhibitors of prostacyclin synthesis, indomethacin and tranylcypromine, and also the specific inhibitor of phospholipase A2, quinacrine, as well as pertussis toxin and the diglyceryl and monoglyceryl lipase inhibitor RHC 80267. Stimulated secretion was also abolished in cells that were either pretreated for 48 hr with phorbol ester to down-regulate protein kinase C or incubated with the protein kinase inhibitor H7. Hydrolysis of phosphatidylinositol by phospholipase A2 appears to be the source of angiogenin-mobilized arachidonate; angiogenin-induced hydrolysis of phosphatidylcholine was not detected. Activation of phospholipase A2 occurs in the absence of an angiogenin-induced calcium flux. The results are discussed in terms of mechanisms of agonist-induced intracellular arachidonate mobilization and relevance to angiogenesis.
The initiation of the activity of the inactive enzyme phospolipase C as the result of a series of molecular signals generated as a consequence of a G-protein coupled receptor binding to its physiological ligand.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
Proc. Natl. Acad. Sci. U.S.A. 85, 5961-5965 (1988)[PubMed:2457905]
Low concentrations of angiogenin activate the inositol-specific phospholipase C of cultured pulmonary artery, umbilical vein, and capillary endothelial cells, promoting a transient increase in the intracellular levels of 1,2-diacylglycerol and inositol trisphosphate. The response is strongly dose dependent with a maximum in the ng/ml concentration range and, for some cell lines, a marked decrease at concentrations greater than 1 ng/ml; e.g., arterial endothelial cells respond weakly to angiogenin concentrations comparable to that in normal human plasma (approximately equal to 400 ng/ml). Chemical modification of the active site of angiogenin or inhibition with placental ribonuclease inhibitor abolishes its activation of endothelial cell phospholipase C; this correlates with the concomitant loss of both intrinsic ribonucleolytic and angiogenic activity. The response to low concentrations of angiogenin is consistent with its potency of inducing vascularization in classical angiogenesis assays. In vivo, endothelial cells are exposed to concentrations of angiogenin higher than that required to elicit a cellular response; it seems likely, therefore, that expression of a surface receptor or some other process must be rate limiting in the cellular response.
Angiogenin, a potent angiogenic factor, binds to endothelial cells and is endocytosed and rapidly translocated to and concentrated in the nucleolus where it binds to DNA. In this study, we report that angiogenin induces transient phosphorylation of protein kinase B/Akt in cultured human umbilical vein endothelial (HUVE) cells. LY294002 inhibits the angiogenin-induced protein kinase B/Akt activation and also angiogenin-induced cell migration in vitro as well as angiogenesis in chick embryo chorioallantoic membrane in vivo without affecting nuclear translocation of angiogenin in HUVE cells. These results suggest that cross-talk between angiogenin and protein kinase B/Akt signaling pathways is essential for angiogenin-induced angiogenesis in vitro and in vivo, and that angiogenin-induced PKB/Akt activation is independent of nuclear translocation of angiogenin in HUVE cells.
Angiogenin, a potent angiogenic factor, binds to endothelial cells and is endocytosed and rapidly translocated to and concentrated in the nucleolus where it binds to DNA. In this study, we report that angiogenin induces transient phosphorylation of protein kinase B/Akt in cultured human umbilical vein endothelial (HUVE) cells. LY294002 inhibits the angiogenin-induced protein kinase B/Akt activation and also angiogenin-induced cell migration in vitro as well as angiogenesis in chick embryo chorioallantoic membrane in vivo without affecting nuclear translocation of angiogenin in HUVE cells. These results suggest that cross-talk between angiogenin and protein kinase B/Akt signaling pathways is essential for angiogenin-induced angiogenesis in vitro and in vivo, and that angiogenin-induced PKB/Akt activation is independent of nuclear translocation of angiogenin in HUVE cells.
Rabbit, pig and mouse angiogenins have been purified from blood serum and characterized, and the rabbit and pig proteins have been sequenced fully. A partial sequence of the mouse protein is consistent with the sequence deduced from the genomic DNA (Bond, M.D. and Vallee, B.L. (1990) Biochem. Biophys. Res. Commun. 171, 988-995). All three angiogenins are homologous to the pancreatic RNases and contain the essential catalytic residues His-13, Lys-40 and His-114, and the 6 half-cystines of the human protein. Like human angiogenin they display extremely low ribonucleolytic activities toward wheat-germ RNA, yeast RNA, poly(C) and poly(U). The rabbit and pig proteins induce neovascularization in vivo and also inhibit protein synthesis in vitro. The interaction of rabbit, pig and bovine angiogenins with placental ribonuclease inhibitor, a potent inhibitor of angiogenin, was examined by fluorescence spectroscopy. Rate and equilibrium binding constants indicate that rabbit angiogenin binds to the inhibitor much like human angiogenin, whereas the pig and bovine proteins show significant differences. A comparison of the five angiogenin sequences now available points to specific residues that are highly conserved among them but differ from the corresponding residues in the RNases. These residues are clustered in particular regions of the three-dimensional structure, two of which contribute to the angiogenic, second-messenger and/or protein synthesis inhibition activities of human angiogenin.
Angiogenin was isolated as a tumor angiogenic factor solely on the basis of its angiogenic activity. Its expression is essential for melanoma progression and metastasis. Many studies have mainly focused on how it induces angiogenesis, which allows further melanoma growth and metastasis. Here, we investigated the effects of angiogenin on melanoma cell growth and studied its influence on the expression and function of the basic fibroblast growth factor. We transfected the angiogenin gene in the sense and antisense orientation into A375 cells, and obtained stable angiogenin under-expressing and over-expressing transfectants. We found that in the angiogenin antisense transfectants, the cell proliferation was decreased and the basic fibroblast growth factor-induced cell proliferation was inhibited, but the expression of basic fibroblast growth factor was increased. In contrast, in the angiogenin sense transfectants, the cell proliferation was increased, and the basic fibroblast growth factor-induced cell proliferation was also increased. The expression of basic fibroblast growth factor, however, was decreased. In conclusion, we demonstrated that, besides its angiogenic activity, angiogenin also directly contributes to A375 cell proliferation and is required for the basic fibroblast growth factor to induce cell proliferation. We also demonstrated that the endogenous angiogenin expression levels affect the expression of basic fibroblast growth factor in A375 cells. By targeting angiogenin, therefore, one may find a potential therapeutic approach to human malignant melanoma.
Evidence
4:
Inferred from Mutant PhenotypeUniProtKB
The roles of His-13 and His-114 in the ribonucleolytic and angiogenic activities of human angiogenin have been investigated by site-directed mutagenesis. Replacement of either residue by alanine (H13A and H114A) decreases enzymatic activity toward tRNA by at least 10,000-fold and virtually abolishes 10,000-fold and virtually abolishes angiogenic activity in the chick embryo chorioallantoic membrane assay. Both the H13A and H114A mutant proteins compete effectively with angiogenin in the latter assay; only a 5-fold molar excess of H13A over unmodified protein is required for complete inhibition. The His----Ala substitutions, however, do not have any significant effect on the interaction of angiogenin with human placental ribonuclease inhibitor, an extremely potent inhibitor of angiogenin (Ki approximately 7 x 10(-16 M) previously shown to interact with another active-site residue, Lys-40. The effects of more conservative replacements-glutamine at position 13 and asparagine at position 114--were also examined. While the enzymatic activity of the H114N mutant was at least 3300-fold less than for the unmodified protein, the H13Q derivative had only 300-fold reduced activity toward tRNA and cytidylyl(3'----5') adenosine. Both substitutions substantially decreased angiogenic activity. The parallel effects on ribonucleolytic and biological activities observed with all four mutant proteins provide strong evidence that the latter activity of angiogenin is dependent on a functional enzymatic active site. The capacity of the H13A and H114A derivatives to compete with angiogenin in the chorioallantoic membrane assay suggests several additional features of the biological mode of action of this protein.
Any process that mediates interactions between a cell and its surroundings. Encompasses interactions such as signaling or attachment between one cell and another cell, between a cell and an extracellular matrix, or between a cell and any other aspect of its environment.
Eur. J. Biochem. 260, 825-832 (1999)[PubMed:10103013]
Human angiogenin is a plasma protein with angiogenic and ribonucleolytic activities. Angiogenin inhibited both DNA replication and proliferation of aortic smooth muscle cells. Binding of 125I-angiogenin to bovine aortic smooth muscle cells at 4 degrees C was specific, saturable, reversible and involved two families of interactions. High-affinity binding sites with an apparent dissociation constant of 0.2 nm bound 1 x 104 molecules per cell grown at a density of 3 x 104.cm-2. Low-affinity binding sites with an apparent dissociation constant of 0.1 micrometer bound 4 x 106 molecules.cell-1. High-affinity binding sites decreased as cell density increased and were not detected at confluence. 125I-angiogenin bound specifically to cells routinely grown in serum-free conditions, indicating that the angiogenin-binding components were cell-derived. Affinity labelling of sparse bovine smooth muscle cells yielded seven major specific complexes of 45, 52, 70, 87, 98, 210 and 250-260 kDa. The same pattern was obtained with human cells. Potential modulators of angiogenesis such as protamine, heparin and the placental ribonuclease inhibitor competed for angiogenin binding to the cells. Together these data suggest that cultured bovine and human aortic smooth muscle cells express specific receptors for human angiogenin.
Any biological process that results in permanent cessation of all vital functions of a cell. A cell should be considered dead when any one of the following molecular or morphological criteria is met: (1) the cell has lost the integrity of its plasma membrane; (2) the cell, including its nucleus, has undergone complete fragmentation into discrete bodies (frequently referred to as \
Angiogenin, a potent angiogenic factor, binds to endothelial cells and is endocytosed and rapidly translocated to and concentrated in the nucleolus where it binds to DNA. In this study, we report that angiogenin induces transient phosphorylation of protein kinase B/Akt in cultured human umbilical vein endothelial (HUVE) cells. LY294002 inhibits the angiogenin-induced protein kinase B/Akt activation and also angiogenin-induced cell migration in vitro as well as angiogenesis in chick embryo chorioallantoic membrane in vivo without affecting nuclear translocation of angiogenin in HUVE cells. These results suggest that cross-talk between angiogenin and protein kinase B/Akt signaling pathways is essential for angiogenin-induced angiogenesis in vitro and in vivo, and that angiogenin-induced PKB/Akt activation is independent of nuclear translocation of angiogenin in HUVE cells.
The chemical reactions and pathways resulting in the formation of diacylglycerol, a glycerol molecule substituted on the 1 and 2 hydroxyl groups with long chain fatty acyl residues.
Proc. Natl. Acad. Sci. U.S.A. 85, 5961-5965 (1988)[PubMed:2457905]
Low concentrations of angiogenin activate the inositol-specific phospholipase C of cultured pulmonary artery, umbilical vein, and capillary endothelial cells, promoting a transient increase in the intracellular levels of 1,2-diacylglycerol and inositol trisphosphate. The response is strongly dose dependent with a maximum in the ng/ml concentration range and, for some cell lines, a marked decrease at concentrations greater than 1 ng/ml; e.g., arterial endothelial cells respond weakly to angiogenin concentrations comparable to that in normal human plasma (approximately equal to 400 ng/ml). Chemical modification of the active site of angiogenin or inhibition with placental ribonuclease inhibitor abolishes its activation of endothelial cell phospholipase C; this correlates with the concomitant loss of both intrinsic ribonucleolytic and angiogenic activity. The response to low concentrations of angiogenin is consistent with its potency of inducing vascularization in classical angiogenesis assays. In vivo, endothelial cells are exposed to concentrations of angiogenin higher than that required to elicit a cellular response; it seems likely, therefore, that expression of a surface receptor or some other process must be rate limiting in the cellular response.
Human angiogenin is a 14-kDa secreted protein with angiogenic and ribonucleolytic activities. Angiogenin is associated with tumour development but is also present in normal biological fluids and tissues. To further address the physiological role of angiogenin, we studied its expression in situ and in vitro, using the human term placenta as a model of physiological angiogenesis. Angiogenin was immunodetected by light and transmission electron microscopy, and its cellular distribution was established by double immunolabelling with cell markers including von Willebrand factor, platelet/endothelial cell adhesion molecule-1 (PECAM-1), CD34, Tie-2, vascular endothelial cadherin (VE-cadherin), vascular endothelial growth factor receptor-2 (VEGF-R2), erythropoeitin receptor (Epo-R), alpha-smooth muscle actin, CD45, cytokeratin 7, and Ki-67. Angiogenin immunoreactivity was detected in villous and extravillous trophoblasts, the trophoblast basement membrane, the endothelial basal lamina, foetal blood vessels, foetal and maternal red blood cells, and amnionic cells. Its expression was confirmed by in situ hybridisation with a digoxygenin-labelled cDNA probe and reverse transcriptase-polymerase chain reaction amplification. Villous cytotrophoblasts, isolated and differentiated in vitro into a functional syncytiotrophoblast, expressed and secreted angiogenin. Given its known biological activities in vitro and its observed pattern of expression, these data suggest that, in human placenta, angiogenin has a role not only in angiogenesis but also in vascular and tissue homeostasis, maternal immune tolerance of the foetus, and host defences.
Eur. J. Biochem. 260, 825-832 (1999)[PubMed:10103013]
Human angiogenin is a plasma protein with angiogenic and ribonucleolytic activities. Angiogenin inhibited both DNA replication and proliferation of aortic smooth muscle cells. Binding of 125I-angiogenin to bovine aortic smooth muscle cells at 4 degrees C was specific, saturable, reversible and involved two families of interactions. High-affinity binding sites with an apparent dissociation constant of 0.2 nm bound 1 x 104 molecules per cell grown at a density of 3 x 104.cm-2. Low-affinity binding sites with an apparent dissociation constant of 0.1 micrometer bound 4 x 106 molecules.cell-1. High-affinity binding sites decreased as cell density increased and were not detected at confluence. 125I-angiogenin bound specifically to cells routinely grown in serum-free conditions, indicating that the angiogenin-binding components were cell-derived. Affinity labelling of sparse bovine smooth muscle cells yielded seven major specific complexes of 45, 52, 70, 87, 98, 210 and 250-260 kDa. The same pattern was obtained with human cells. Potential modulators of angiogenesis such as protamine, heparin and the placental ribonuclease inhibitor competed for angiogenin binding to the cells. Together these data suggest that cultured bovine and human aortic smooth muscle cells express specific receptors for human angiogenin.
Any process that stops, prevents, or reduces the frequency, rate or extent of the chemical reactions and pathways resulting in the formation of proteins by the translation of mRNA.
A developmental process, independent of morphogenetic (shape) change, that is required for an oocyte to attain its fully functional state. Oocyte maturation commences after reinitiation of meiosis commonly starting with germinal vesicle breakdown, and continues up to the second meiotic arrest prior to fertilization.
OBJECTIVE: To determine the concentration of angiogenic factors (vascular endothelial growth factor [VEGF], basic fibroblast growth factor [bFGF], and angiogenin) in the follicular fluid (FF) and oocyte-cumulus complex culture medium (CM) of women undergoing IVF and to investigate the association of the concentrations with the maturity and fertilization of the oocyte. DESIGN: Prospective study. SETTING: Academic tertiary-care institution. PATIENT(S): IVF patients with unexplained or tubal factor infertility. INTERVENTION(S): Analysis of VEGF, bFGF, and angiogenin FF and CM concentrations. MAIN OUTCOME MEASURE(S): Oocyte maturity and fertilization and FF and CM angiogenic factor concentrations. RESULT(S): VEGF, bFGF, and angiogenin were determined in FF and CM. FF angiogenin concentrations were significantly higher when the oocyte was mature versus immature. CM VEGF concentrations were significantly higher when the oocyte was nonfertilized versus fertilized. Positive correlations were observed between angiogenic factors in CM. CONCLUSION(S): VEGF, bFGF, and angiogenin (determined for the first time) are secreted in the FF and CM. Elevated CM VEGF concentrations, probably implying oocyte-cumulus complex hypoxia, are negatively associated with oocyte fertilization. Elevated FF angiogenin concentrations are positively associated with oocyte maturity, possibly indicating angiogenin's biological role beyond neovascularization.
The aim of this study was to quantitate of vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), and angiogenin in follicular fluid (FF) and to correlate the levels of these substances with oocyte maturation. FF were aspirated from women undergoing in vitro fertilization and embryo transfer. Sera were collected from women with normal menstrual cycles. VEGF in FFs and sera were measured by enzyme linked immunosorbent assay. VEGF, HGF, and angiogenin mRNA expression aspirated folliculars cell was analyzed by reverse transcription and polymerase chain reaction (RT-PCR). The concentrations of VEGF, HGF, and angiogenin in FF were significantly higher than those in serum (P<0.001). VEGF, HGF, and angiogenin mRNA in the aspirated follicles cell was detected by RT-PCR. HGF levels were higher in FF containing mature oocyte. The levels of VEGF in FF containing mature oocytes in women under 39 years of age were significantly lower than those in FF from women more than 40 years old (P<0.01). Our data suggest that VEGF, HGF, and angiogenin may play an important role in follicular growth and development, that VEGF levels in FF appear to be age-dependent; and that VEGF and HGF levels might be valuable biochemical markers of oocyte maturation.
The process whose specific outcome is the progression of the placenta over time, from its formation to the mature structure. The placenta is an organ of metabolic interchange between fetus and mother, partly of embryonic origin and partly of maternal origin.
Human angiogenin, a 14-kDa non-glycosylated polypeptide with both angiogenic and ribonucleolytic activities, is implicated in angiogenesis, a complex process of proliferation and formation of new capillary blood vessels from existing blood vessels. Placental growth requires extensive angiogenesis, which develops its vascular structure in both fetal chorionic villi and maternal deciduas. In this study, we investigated the expression profiles of angiogenin in placental villi from early and late gestation at both mRNA and protein levels using explant cultures in vitro followed by RT-PCR, immunoblot, and immunohistochemical analyses. From functionally active placental explants, angiogenin was detected in conditioned media of all the samples from first trimester and term group. The mean levels of angiogenin produced by term villi were found to be 2.6-, 2.1-, and 2.2-fold higher (P < 0.01) than first trimester villi at 24, 48, and 72 hr of culture, respectively. Expression profiles of angiogenin from term and first trimester villi seem to agree with its mRNA levels and immunoblot analysis; the expression in term villi was twice that in first trimester villi. The presence of angiogenin in placental villi and upregulation of its production towards term indicate that angiogenin production by the placenta is specific to the developmental stage. In conclusion, the observed changes in the localization and mRNA expression of angiogenin during placental development raise the possibility that it is involved in morphological and angiogenic changes in this endocrine organ vital to the successful fetal outcome during pregnancy.
Proc. Natl. Acad. Sci. U.S.A. 94, 2204-2209 (1997)[PubMed:9122172]
Angiogenin stimulates both [3H]thymidine incorporation and proliferation of human endothelial cells in sparse cultures. Under these conditions, a 170-kDa cell surface protein can be detected that binds angiogenin specifically. Angiogenin-stimulated cell growth is concentration-dependent and is completely inhibited by an anti-angiogenin monoclonal antibody, but not by a nonimmune control antibody. It is not affected by the nonangiogenic homolog, RNase A, nor by other angiogenic proteins, such as basic fibroblast growth factor and its antibody. Results suggest that under specific conditions, endothelial cells express an angiogenin receptor that may mediate angiogenin-stimulated DNA synthesis and proliferation and play an important role in angiogenin-induced angiogenesis.
Proc. Natl. Acad. Sci. U.S.A. 95, 9791-9795 (1998)[PubMed:9707554]
A class of angiogenesis inhibitor has emerged from our mechanistic study of the action of angiogenin, a potent angiogenic factor. Neomycin, an aminoglycoside antibiotic, inhibits nuclear translocation of human angiogenin in human endothelial cells, an essential step for angiogenin-induced angiogenesis. The phospholipase C-inhibiting activity of neomycin appears to be involved, because U-73122, another phospholipase C inhibitor, has a similar effect. In contrast, genistein, oxophenylarsine, and staurosporine, inhibitors of tyrosine kinase, phosphotyrosine phosphatase, and protein kinase C, respectively, do not inhibit nuclear translocation of angiogenin. Neomycin inhibits angiogenin-induced proliferation of human endothelial cells in a dose-dependent manner. At 50 microM, neomycin abolishes angiogenin-induced proliferation but does not affect the basal level of proliferation and cell viability. Other aminoglycoside antibiotics, including gentamicin, streptomycin, kanamycin, amikacin, and paromomycin, have no effect on angiogenin-induced cell proliferation. Most importantly, neomycin completely inhibits angiogenin-induced angiogenesis in the chicken chorioallantoic membrane at a dose as low as 20 ng per egg. These results suggest that neomycin and its analogs are a class of agents that may be developed for anti-angiogenin therapy.
Angiogenin, a potent angiogenic factor, binds to endothelial cells and is endocytosed and rapidly translocated to and concentrated in the nucleolus where it binds to DNA. In this study, we report that angiogenin induces transient phosphorylation of protein kinase B/Akt in cultured human umbilical vein endothelial (HUVE) cells. LY294002 inhibits the angiogenin-induced protein kinase B/Akt activation and also angiogenin-induced cell migration in vitro as well as angiogenesis in chick embryo chorioallantoic membrane in vivo without affecting nuclear translocation of angiogenin in HUVE cells. These results suggest that cross-talk between angiogenin and protein kinase B/Akt signaling pathways is essential for angiogenin-induced angiogenesis in vitro and in vivo, and that angiogenin-induced PKB/Akt activation is independent of nuclear translocation of angiogenin in HUVE cells.
Proc. Natl. Acad. Sci. U.S.A. 86, 1573-1577 (1989)[PubMed:2646638]
Angiogenin stimulates capillary and umbilical vein endothelial cell prostacyclin secretion but not that of prostaglandins of the E series. The response was quantitated by radioimmunoassay and by [3H]arachidonate labeling followed by analysis of the secreted prostaglandins. The stimulated secretion lasts for several minutes and is optimal at 2-4 min. The dose-response (peak at 1-10 ng/ml) is similar to that previously observed for activation of endothelial cell phospholipase C. Stimulated secretion was blocked by pretreatment with the inhibitors of prostacyclin synthesis, indomethacin and tranylcypromine, and also the specific inhibitor of phospholipase A2, quinacrine, as well as pertussis toxin and the diglyceryl and monoglyceryl lipase inhibitor RHC 80267. Stimulated secretion was also abolished in cells that were either pretreated for 48 hr with phorbol ester to down-regulate protein kinase C or incubated with the protein kinase inhibitor H7. Hydrolysis of phosphatidylinositol by phospholipase A2 appears to be the source of angiogenin-mobilized arachidonate; angiogenin-induced hydrolysis of phosphatidylcholine was not detected. Activation of phospholipase A2 occurs in the absence of an angiogenin-induced calcium flux. The results are discussed in terms of mechanisms of agonist-induced intracellular arachidonate mobilization and relevance to angiogenesis.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a hormone stimulus.
J. Clin. Endocrinol. Metab. 85, 3352-3355 (2000)[PubMed:10999833]
Angiogenesis is an essential event during the development of the ovarian follicle and ensuing formation of the corpus luteum. We investigated the presence of angiogenin, a potent inducer of angiogenesis, and the regulatory mechanisms of its production in the human ovary. Follicular fluid (FF) and granulosa cells (GCs) were collected from women undergoing in vitro fertilization and embryo transfer. The presence of angiogenin in FF and GCs was demonstrated by Western blot analysis. The production of angiogenin by cultured GCs was stimulated with the addition of human CG or cAMP or under the hypoxic milieu. Concentrations of angiogenin in FF from an individual follicle were positively correlated with those of progesterone, but not estradiol and testosterone. Given the presence of angiogenin in FF and up-regulation of its production by human CG and hypoxia, it seems logical to assume that angiogenin may play a role as a local angiogenic factor in the human ovary.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus indicating lowered oxygen tension. Hypoxia, defined as a decline in O2 levels below normoxic levels of 20.8 - 20.95%, results in metabolic adaptation at both the cellular and organismal level.
J. Clin. Endocrinol. Metab. 85, 3352-3355 (2000)[PubMed:10999833]
Angiogenesis is an essential event during the development of the ovarian follicle and ensuing formation of the corpus luteum. We investigated the presence of angiogenin, a potent inducer of angiogenesis, and the regulatory mechanisms of its production in the human ovary. Follicular fluid (FF) and granulosa cells (GCs) were collected from women undergoing in vitro fertilization and embryo transfer. The presence of angiogenin in FF and GCs was demonstrated by Western blot analysis. The production of angiogenin by cultured GCs was stimulated with the addition of human CG or cAMP or under the hypoxic milieu. Concentrations of angiogenin in FF from an individual follicle were positively correlated with those of progesterone, but not estradiol and testosterone. Given the presence of angiogenin in FF and up-regulation of its production by human CG and hypoxia, it seems logical to assume that angiogenin may play a role as a local angiogenic factor in the human ovary.
Angiogenin, a 14.2 kD polypeptide that was originally noted for its angiogenic activity, is now increasingly recognized to have a multiplicity of biological roles in both physiological and pathological conditions. In breast cancer, there are conflicting studies questioning the role of angiogenin. Here, the pattern of expression of angiogenin during the transition from normal breast tissue to ductal carcinoma in situ and invasive carcinoma is reported together with the correlates between the level of angiogenin in 239 invasive carcinomas and standard clinicopathological parameters, hypoxia-inducible factor (HIF)-1 alpha and the HIF-1 alpha target gene DEC-1. This study shows that angiogenin expression is up-regulated in the cytoplasmic and nuclear compartments in in situ carcinoma and invasive carcinoma compared with normal breast tissue and that angiogenin expression in invasive carcinomas is significantly positively associated with high tumour grade (p = 0.03), positive oestrogen receptor (ER) status (p = 0.01), HIF-1 alpha (p = 0.001) and DEC 1 (p = 0.001), but not with patient age (p = 0.8), tumour size (p = 0.25), lymph node status (p = 0.69), epidermal growth factor receptor (p = 0.56) or microvessel density (p = 0.32). No difference in relapse-free (p = 0.26) or overall (p = 0.63) survival was observed in patients stratified by angiogenin expression. This study suggests that angiogenin may be important in breast cancer progression and that, through its relationship with ER, it may be a target for tamoxifen.
OBJECTIVE: Many processes that are involved in cellular invasion, including blastocyst implantation, placental development, and rapidly growing tumors, occur in reduced oxygen environments. It has been surmised that oxygen tension could regulate the cytotrophoblast ability to differentiate and, as a consequence, to express proteins that are critical for placentation. The objective of the current investigation was therefore to test the hypothesis that placental tissues and trophoblast cells in culture, under low oxygen tension, release angiogenic factors that could affect vascular behavior and invasive potential, thus providing a link between abnormal placentation and maternal vascular abnormality. METHODS: Functionally active term placental explant culture and trophoblast cultures were used to demonstrate the secretion profiles of angiogenin and vascular cell adhesion molecule-1 (VCAM-1), and the real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) technique was employed to demonstrate the mRNA expression under both normoxic and hypoxic conditions. RESULTS: A significant increase in the secretion (P <.01) and mRNA expression (P <.01) of angiogenin and a significant decrease in the secretion (P <.04) and mRNA expression (P <.03) of VCAM-1 from both term placental explants and trophoblast cultures subjected to hypoxia in vitro were observed. CONCLUSION: Because the primary defect in uteroplacental insufficiency is placental maldevelopment probably associated with hypoxia in situ, this study provides molecular evidence to indicate that the differential expression and secretion of angiogenic factors may play an important role in these pathologic conditions.
BACKGROUND: Chronic low oxygen in the tubulointerstitial area is a crucial cause of renal degradation and tubulointerstitial damage. Previous reports have suggested that the maintenance of renal blood flow plays a role in the suppression of progressive renal damage. Neovascularization is important for the maintenance of blood flow. We studied the production of angiogenic factors by culturing renal proximal tubular epithelial cells (PTEC) under hypoxic conditions. METHODS: Cultured PTEC were exposed to normal and low-oxygen conditions. The levels of angiogenin (ANG) and vascular endothelial growth factor (VEGF) in the cell supernatants were measured by enzyme-linked immunosorbent assay. The messenger RNAs (mRNAs) of ANG and VEGF in the PTEC were examined by real-time reverse transcriptase polymerase chain reaction (real-time RT-PCR). The presence of ANG, VEGF and hypoxia-inducible factor-1 (HIF-1) was studied by immunofluorescence techniques. The effect of cobalt chloride (CoCl(2)), which is an HIF-1 inducer, on the production of ANG and VEGF was also examined in order to elucidate the contribution of the HIF-1 pathway to the production of these cytokines. RESULTS: ANG and VEGF were demonstrated to exist in the cell supernatants, and ANG and VEGF mRNAs were detected in the PTEC. Hypoxic conditions stimulated the secretion of ANG (2.5-fold vs normoxia, P<0.001) and VEGF (3.2-fold vs normoxia, P<0.001) by PTEC. Hypoxic conditions increased the mRNA expression of ANG for 6 h (1.38-fold vs normoxia, P<0.05) and VEGF for 24 h (2.04-fold vs normoxia, P<0.01). Hypoxic conditions also enhanced ANG, VEGF and HIF-1 protein expression in PTEC. The CoCl(2) increased the secretion of ANG (5.2-fold vs control, P<0.0001) and VEGF (2.3-fold vs control, P<0.0001) by PTEC. CONCLUSION: Under hypoxic conditions, the ANG and VEGF secreted by PTEC may modulate angiogenesis and vascular remodeling in the renal interstitium via an increase in the production of HIF-1.
Angiogenin is an angiogenic protein known to play a role in rRNA transcription in endothelial cells. Nuclear translocation of angiogenin in endothelial cells decreases as cell density increases and ceases when cells are confluent. Here we report that angiogenin is constantly translocated to the nucleus of HeLa cells in a cell density-independent manner. Down-regulation of angiogenin expression by antisense and RNA interference results in a decrease in rRNA transcription, ribosome biogenesis, proliferation, and tumorigenesis both in vitro and in vivo. Exogenous angiogenin rescues the cells from antisense and RNA interference inhibition. The results showed that angiogenin is constitutively translocated into the nucleus of HeLa cells where it stimulates rRNA transcription. Thus, besides its angiogenic activity, angiogenin also plays a role in cancer cell proliferation.
Protein involved in angiogenesis, the sprouting or splitting of capillaries from pre-existing vasculature. Angiogenesis plays an important role for example during embryonic development, normal growth of tissues and maintenance of the normal vasculature, wound healing, tumor growth and metastasis.
Protein involved in differentiation, the developmental process of a multicellular organism by which cells become specialized for particular functions. Differentiation requires selective expression of the genome; the fully differentiated state may be preceded by a stage in which the cell is already programmed for differentiation but is not yet expressing the characteristic phenotype determination. Also used for fungal conidiation proteins, and for some bacteria that present specialization of function in cell types, such as Caulobacter crescentus.
Protein involved in development, the process whereby a multicellular organism develops from its early immature forms, e.g., zygote, larva, embryo, into an adult.
Enzyme which catalyzes hydrolysis reaction, i.e. the addition of the hydrogen and hydroxyl ions of water to a molecule with its consequent splitting into two or more simpler molecules.
Enzyme that degrades nucleic acids into shorter oligonucleotides or single nucleotide subunits by hydrolyzing sugar-phosphate bonds in the nucleic acid backbone.
Protein which blocks the synthesis of proteins (translation) through various mechanisms, including hydrolysis of cellular tRNA, and inactivation of the 60S subunits of eukaryotic ribosome.
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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