α2A-Adrenergic receptors activate protein kinase C in human platelets via a pertussis toxin-sensitive G-protein

Abstract

4,4'-Diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS) stimulates human platelets via α2A-adrenergic receptor-mediated activation of protein kinase C (PKC) independent of the phospholipase C pathway. Here we show, that in permeabilized platelets activation of PKC by DIDS (20 μM), measured as 32P incorporation in pleckstrin, is completely inhibited by guanosine 5'-(2-O-thio)diphosphate (200 μM), an inhibitor of heterotrimeric G-proteins. Also pertussin toxin (4 μg ml), which ADP-ribosylates the α-subunits of Gi's and Go, prevents pleckstrin phosphorylation by DIDS. N-Ethylmaleimide (50 μM), which uncouples Gi from α2A-adrenoceptors, inhibits pleckstrin phosphorylation by DIDS in intact pl..