Activation of cytosolic phospholipase A2-{alpha} as a novel mechanism regulating endothelial cell cycle progression and angiogenesis.
Release of endothelial cells from contact-inhibition and cell cycle re-entry is required for the induction of new blood vessel formation by angiogenesis. Using a combination of chemical inhibition, loss of function, and gain of function approaches, we demonstrate that endothelial cell cycle re-entry, S phase progression, and subsequent angiogenic tubule formation are dependent upon the activity of cytosolic phospholipase A(2)-alpha (cPLA(2)alpha). Inhibition of cPLA(2)alpha activity and small interfering RNA (siRNA)-mediated knockdown of endogenous cPLA(2)alpha reduced endothelial cell proliferation. In the absence of cPLA(2)alpha activity, endothelial cells exhibited retarded progression from G(1) through S phase, displayed reduced cyclin A/cdk2 expression, and generated less arachidonic acid. In quiescent endothelial cells, cPLA(2)alpha is inactivated upon its sequestration at the Golgi apparatus. Upon the stimulation of endothelial cell proliferation, activation of cPLA(2)alpha by release from the Golgi apparatus was critical to the induction of cyclin A expression and efficient cell cycle progression. Consequently, inhibition of cPLA(2)alpha was sufficient to block angiogenic tubule formation in vitro. Furthermore, the siRNA-mediated retardation of endothelial cell cycle re-entry and proliferation was reversed upon overexpression of an siRNA-resistant form of cPLA(2)alpha. Thus, activation of cPLA(2)alpha acts as a novel mechanism for the regulation of endothelial cell cycle re-entry, cell cycle progression, and angiogenesis.
Herbert
Shane P
SP
Endothelial Cell Biology Unit, Institute of Molecular and Cellular Biology, Leeds Institute of Genetics, Health, and Therapeutics, University of Leeds, Leeds LS2 9JT, United Kingdom.
Odell
Adam F
AF
Ponnambalam
Sreenivasan
S
Walker
John H
JH
D016718:Arachidonic Acid / Q000378:metabolism; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D003600:Cytosol; D020405:Dermis / Q000166:cytology / Q000201:enzymology; D004730:Endothelium, Vascular / Q000166:cytology*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006056:Golgi Apparatus / Q000378:metabolism; D054513:Group IV Phospholipases A2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D018919:Neovascularization, Physiologic; D034741:RNA, Small Interfering / Q000494:pharmacology; D014471:Umbilical Veins / Q000166:cytology / Q000201:enzymology
D034741:RNA, Small Interfering; D016718:Arachidonic Acid; D054513:Group IV Phospholipases A2