Alpha 2A-adrenergic receptors activate protein kinase C in human platelets via a pertussis toxin-sensitive G-protein

• Published in: FEBS letters Vol. 339; no. 1-2; p. 79
• Main Authors: Nieuwland, R, Wijburg, O L, van Willigen, G, Akkerman, J W
• Format: Journal Article
• Language: English
• Published: England 14-02-1994
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; Adenosine Diphosphate Ribose - blood; Blood Platelets - drug effects; Blood Platelets - enzymology; Blood Proteins - metabolism; Cell Membrane Permeability; Enzyme Activation; Ethylmaleimide - pharmacology; GTP-Binding Proteins - physiology; Humans; Pertussis Toxin; Phosphoproteins; Phosphorylation; Protein Kinase C - blood; Receptors, Adrenergic, alpha - physiology; Tetradecanoylphorbol Acetate - pharmacology; Virulence Factors, Bordetella - pharmacology
• ISSN: 0014-5793

4,4'-Diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS) stimulates human platelets via alpha 2A-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 microM), measured as 32P incorporation in pleckstrin, is completely inhibited by guanosine 5'-(2-O-thio)diphosphate (200 microM), an inhibitor of heterotrimeric G-proteins. Also pertussin toxin (4 micrograms/ml), which ADP-ribosylates the alpha-subunits of Gi's and Go, prevents pleckstrin phosphorylation by DIDS. N-Ethylmaleimide (50 microM), which uncouples Gi from alpha 2A-adrenoceptors, inhibits pleckstrin phosphorylation by DIDS in intact platelets. Activation of PKC by 55 nM phorbol 12-myristate 13-acetate and 500 nM platelet-activating factor are not disturbed by NEM. DIDS inhibits by 40 +/- 5% (n = 4) the pertussis toxin-catalyzed [32P]ADP-ribosylation of a 41 kDa protein fraction previously shown to contain the alpha-subunits of Gi alpha-1, Gi alpha-2 and Gi alpha-3. Thus, the alpha 2A-adrenergic receptor activates PKC via a G-protein of the Gi-family.