Regulation of vascular endothelial growth factor binding and activity by extracellular pH.
Angiogenesis, the growth of new blood vessels, is regulated by a number of factors, including hypoxia and vascular endothelial growth factor (VEGF). Although the effects of hypoxia have been studied intensely, less attention has been given to other extracellular parameters such as pH. Thus, the present study investigates the consequences of acidic pH on VEGF binding and activity in endothelial cell cultures. We found that the binding of VEGF165 and VEGF121 to endothelial cells increased as the extracellular pH was decreased from 7.5 to 5.5. Binding of VEGF165 and VEGF121 to endothelial extracellular matrix was also increased at acidic pH. These effects were, in part, a reflection of increased heparin binding, because VEGF165 and VEGF121 showed increased retention on heparin-Sepharose at pH 5.5 compared with pH 7.5. Consistent with these findings, soluble heparin competed for VEGF binding to endothelial cells under acidic conditions. However, at neutral pH (7.5) low concentrations of heparin (0.1-1.0 microg/ml) potentiated VEGF binding. Extracellular pH also regulated VEGF activation of the extracellular signal-regulated kinases 1 and 2 (Erk1/2). VEGF165 and VEGF121 activation of Erk1/2 at pH 7.5 peaked after 5 min, whereas at pH 6.5 the peak was shifted to 10 min. At pH 5.5, neither VEGF isoform was able to activate Erk1/2, suggesting that the increased VEGF bound to the cells at low pH was sequestered in a stored state. Therefore, extracellular pH might play an important role in regulating VEGF interactions with cells and the extracellular matrix, which can modulate VEGF activity.
Goerges
Adrienne L
AL
Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Nugent
Matthew A
MA
D000818:Animals; D001011:Aorta; D001667:Binding, Competitive; D002417:Cattle; D016228:Endothelial Growth Factors / Q000378:metabolism* / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005109:Extracellular Matrix / Q000378:metabolism; D006493:Heparin / Q000008:administration & dosage / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism* / Q000494:pharmacology; D007457:Iodine Radioisotopes; D008222:Lymphokines / Q000378:metabolism* / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D007457:Iodine Radioisotopes; D008222:Lymphokines; D011994:Recombinant Proteins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D006493:Heparin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases