Role of intracellular calcium in the angiotensin II-mediated tyrosine phosphorylation and dephosphorylation of PLC-gamma 1.
Angiotensin II induces the rapid temporal tyrosine phosphorylation and activation of phospholipase C-gamma 1 (PLC-gamma 1) and the elevation of intracellular calcium levels. To investigate the relationship of these intracellular signaling events, rat aortic smooth muscle cells were treated with the calcium chelator BAPTA-AM, the calcium channel blocker verapamil, the intracellular calcium antagonist TMB-8, and the calcium ionophore ionomycin. The effects of these agents on PLC-gamma 1 tyrosine phosphorylation were then measured. We found that treatment of these cells with the calcium inhibitors augmented the basal level of PLC-gamma 1 tyrosine phosphorylation, without changing the peak level of tyrosine phosphorylation induced by angiotensin II. The rapid dephosphorylation of PLC-gamma 1 that follows angiotensin II stimulation was prevented by these calcium antagonists. In contrast, angiotensin II-induced tyrosine phosphorylation of PLC-gamma 1 was inhibited by ionomycin. These results suggest that the angiotensin II-induced tyrosine phosphorylation of PLC-gamma 1 is calcium-independent, while the dephosphorylation is calcium-dependent.
Harp
J B
JB
Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Sayeski
P P
PP
Scanlon
M
M
Bernstein
K E
KE
Marrero
M B
MB
D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D001011:Aorta; D002118:Calcium / Q000037:antagonists & inhibitors / Q000502:physiology*; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D007424:Intracellular Fluid; D015759:Ionomycin / Q000494:pharmacology; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular; D051966:Phospholipase C gamma; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D010738:Type C Phospholipases / Q000187:drug effects / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
D002614:Chelating Agents; D007527:Isoenzymes; D000804:Angiotensin II; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D014443:Tyrosine; D004533:Egtazic Acid; D015759:Ionomycin; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D002118:Calcium