We investigated the regulation of 1 pS Ca2+ channels by PDGF in cultured rat mesangial cells. In cell-attached patches, intrapipette PDGF-BB (50 ng/ml) increased NPo (channel number X open probability) from 0.0002 ± 0.0001 to 0.33 ±0.02 (mean ±SE; P<0.003; n=6). Tyrosine kinase inhibition ( 100 uM genistein or 10 uM tryphostin9) abolished PDGF-induced channel activation (P<0.02; n=6). In inside-out patches, the effect of tyrosine kinase inhibition could be reversed by cytoplasmic exposure to a non-hydrolyzable GTP analogue (200 μM GTPyS) (P<0.02; n=4). In contrast, 200 μM GDPβS inhibited PDGF-induced channels (P<0.04; n=6). Pertussis toxin (250 ng/mi PTX) had no effect on PDGF-induced channel activity (P=0.45; n=6). When excised patches were exposed to anti-Aas antibody (5 ug/ml), PDGF-induced channel activity was abolished (PO.007; n=6). Western immunoblots revealed that genistein blocks PDGF-induced membrane translocation of growth factor receptor-binding protein 2 and the guanine nucleotide exchange factor, Son of Sevenless, to form a complex with the PDGFβ receptor itself. In mesangial cells, intrinsic tyrosine kinase activity of the PDGFβ receptor stimulates 1 pS Ca2+ channels via downstream activation of the PTX-insensitive GTP-binding protein, p21-Ras.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology