Inhibition by cyclic AMP of guanine nucleotide‐induced activation of phosphoinositide‐specific phospholipase C in human platelets

FEBS Letters

Nagao, Seiji¹  Okano, Yukio¹  Yada, Yukihiro¹  Nozawa, Yoshinori¹ 

[1] Department of Biochemistry, Gifu University School of Medicine, Tsukasamachi 40, Gifu 500, Japan

关键词: Phosphoinositide-specific phospholipase C;    GTP-binding protein;    cyclic AMP-dependent protein kinase;    (Human platelet);    cAMP;    cyclic AMP;    dbcAMP;    dibutyryl cAMP;    GTPγS;    guanosine 5′-(3-O-thio)triphosphate;    IP3;    inositol 1;    4;    5-trisphosphate;    PIP2;    phosphatidylinositol 4;    5-bisphosphate;    Gpp(NH)p;    guanosine 5′-(β;    γ-imido)triphosphate;    App(NH)p;    adenosine 5′-(β;    γ-imido)triphosphate;    8-N 3-GTP;    8-azido-guanosine 5′-triphosphate;    H-8;    N-[2-(methylamino)ethyl]-5-isoquinoline sulfonamide dihydrochloride;    G-protein;    GTP-binding protein;    Gs and Gi;    the stimulatory and inhibitory G-proteins;    respectively;    of adenylate cyclase;    A-kinase;    cAMP-dependent protein kinase;    A-membranes;    membranes isolated from dbcAMP-pretreated platelets;    B-membranes;    membranes prepared from untreated platelets and then incubated with cAMP in the presence of Mg2+ and ATP;   

DOI  :  10.1016/0014-5793(89)80503-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Phosphoinositide-specific phospholipase C (PLC) activity of human platelet membranes was activated by the nonhydrolyzable guanine nucleotide GTPγS. This activation did not occur in either membranes prepared from dibutyryl cyclic AMP-pretreated platelets (A-membranes) or those prepared from untreated cells and subsequently incubated with cyclic AMP (cAMP) (B-membranes). This cAMP-mediated inhibition was abolished in the presence of inhibitors of cAMP-dependent protein kinase (A-kinase), suggesting that the inhibition was due to phosphorylation of (a) protein component(s). No significant differences were observed in the basal PLC activity and the extent of pertussis toxin-catalyzed ADP-ribosylation among control membranes and the two types of phosphorylated membranes (A- and B-membranes). GTP-binding activities of G_s, G_i and GTP-binding proteins of lower molecular masses were not altered by the phosphorylation of the membranes. These findings suggest that a GTP-binding protein is involved in the GTPγS-mediated activation of PLC and that cAMP (plus A-kinase) inhibits this activation by phosphorylating a membrane protein (probably a 240-kDa protein), rather than the GTP-binding protein or PLC itself. It is likely that this phosphorylation uncouples the GTP-binding protein from PLC.

【 授权许可】

Unknown