Angiotensin II activates the beta 1 isoform of phospholipase C in vascular smooth muscle cells.
Vascular smooth muscle cells (VSMC) contribute to the pathophysiology of hypertension through cell growth and contraction, and phospholipase C (PLC) is a critical effector enzyme in growth factor and vasoconstrictor signaling. There is indirect evidence that angiotensin II (ANG II) receptors are linked to the PLC-beta isoform signaling pathways. However, recent studies suggest that PLC-beta isoforms may not be expressed in VSMC. Our data demonstrate that in human aortic VSMC, PLC-beta 1 and PLC-gamma 1 proteins were detected by immunoblot analysis, and PLC-beta 1 mRNA was identified by reverse transcriptase-polymerase chain reaction in rat aortic VSMC. Incubation of permeabilized VSMC with anti-PLC-beta 1 or anti-Gq alpha antibodies inhibited ANG II-dependent inositol polyphosphate (IP) formation, while anti-PLC-gamma 1 antibodies did not inhibit ANG II-regulated IP formation. Conversely, anti-PLC-gamma 1 antibodies completely abolished platelet-derived growth factor (PDGF)-dependent IP generation, whereas anti-PLC-beta 1 antibodies had no effect on PDGF-induced PLC activation. Inhibition of tyrosine phosphorylation with genistein or herbimycin A did not diminish ANG II-stimulated IP formation or cytosolic free Ca2+ concentration transients, thereby confirming that ANG II signals via a PLC-gamma 1-independent mechanism. In summary, PLC-beta 1 and PLC-gamma 1 are expressed in human aortic VSMC, and PLC-beta 1 is the isoform that is critical for ANG II-regulated PLC signaling in these cells.
Schelling
J R
JR
Rammelkamp Center for Research, Case Western Reserve University School of Medicine, Cleveland 44109, Ohio, USA.
Nkemere
N
N
Konieczkowski
M
M
Martin
K A
KA
Dubyak
G R
GR
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000502:physiology; D006801:Humans; D015151:Immunoblotting; D007295:Inositol Phosphates / Q000096:biosynthesis; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014158:Transcription, Genetic; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism*
D007295:Inositol Phosphates; D007527:Isoenzymes; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D000804:Angiotensin II; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins