Regulation of PDGF-beta receptor-operated Ca2+ channels by phospholipase C-gamma 1 in glomerular mesangial cells.

Platelet-derived growth factor (PDGF)-induced Ca2+ signaling mechanisms were examined in cultured rat glomerular mesangial cells. PDGF-BB stimulated the tyrosine phosphorylation of phospholipase C (PLC)-gamma 1, the formation of a PLC-gamma 1/PDGF-beta receptor membrane complex, and the generation of intracellular inositol 1,4,5-trisphosphate (IP3). Preincubation with a tyrosine kinase inhibitor (genistein) abolished these PDGF-induced responses. Activation of 1-pS Ca2+ channels in cell-attached patches by intrapipette PDGF-BB was also abolished by tyrosine kinase inhibition. In the absence of PDGF-BB, channels were activated in cell-attached patches exposed to intrapipette thapsigargin (IP3-independent releaser of intracellular Ca2+ stores) and in excised inside-out patches exposed to increasing "cytoplasmic" Ca2+ (10(-8) to 10(-6) M). In cell-attached patches, channel activation by PDGF-BB was abolished when extracellular Ca2+ was < 1 mM. In glomerular mesangial cells 1) PDGF-BB stimulates tyrosine phosphorylation of PLC-gamma 1, PDGF-beta receptor/PLC-gamma 1 membrane complex formation, IP3 production, and 1-pS Ca2+ channel activity; 2) all four PDGF-induced responses are abolished by tyrosine kinase inhibition; 3) PDGF receptor-operated Ca2+ channels are sensitive to both intra- and extracellular Ca2+.