The activation of phospholipase D by endothelin-1, angiotensin II, and platelet-derived growth factor in vascular smooth muscle A10 cells is mediatedby small G proteins of the ADP-ribosylation factor family

We show here that A10 cells express the phospholipase D (PLD) isoforms PLD1 b and PLD2. The activation of PLD in these cells by angiotensin II (AngII), endothelin-l (ET-1), and platelet-derived growth factor (PDGF) was found t o be sensitive to inhibitors of the activation of ADP-ribosylation factor ( ARF) but not to blockers of Rho protein function. PDGF, AngII, and ET-1 ind uced the binding of ARF proteins to cell membranes in a permeabilized cell assay. Cells permeabilized and depleted of ARF were no longer sensitive to stimulation with AngII, ET-1, or PDGF, but the addition of recombinant myri stoylated human ARF1 restored agonist-dependent PLD activity. Expression of dominant negative ARF mutants blocked receptor-dependent activation of PLD . PLD activity was also potently stimulated by treatment with phorbol ester s, but this activity was only partially inhibited by brefeldin A or by the overexpression of ARF dominant negative mutants. Transient expression of ca talytically inactive mutants of PLD2, but not PLD1, inhibited significantly PDGF- and AngII-dependent PLD activity. We conclude: 1) the activation of PLD by cell surface receptors occurs primarily by an ARF-dependent mechanis m in A10 cells, whereas the activation of PLD by protein kinase C-dependent pathways is only partially dependent on the regulation of ARF proteins; an d 2) cell surface receptors, such as AngII and PDGF, signal primarily via P LD2 in A10 cells.