Muscarinic receptors mediate phospholipase C-dependent activation of protein kinase B via Ca2+, ErbB3, and phosphoinositide 3-Kinase in 1321N1 astrocytoma cells

Xiuwen Tang, Ian H. Batty, C. Peter Downes

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    39 Citations (Scopus)

    Abstract

    In 1321N1 astrocytoma cells, heterotrimeric G-protein-coupled receptors that activate phosphoinositide-specific phospholipase Cbeta (PLCbeta) isoforms via G(q), induced a prolonged activation of protein kinase B (PKB) after a short delay. For example, the effect of carbachol acting on M3 muscarinic receptors is blocked by wortmannin, suggesting it is mediated via a phosphoinositide 3-kinase (PI 3-kinase). In support of this, carbachol increased PI 3-kinase activity in PI 3-kinase (p85) immunoprecipitates. The pathway linking PLC-coupled receptors to PI 3-kinase was deduced to involve phosphoinositide hydrolysis and Ca2+-dependent ErbB3 transactivation but not protein kinase C on the basis of the following evidence: (i) inhibition of carbachol stimulated PLC by pretreatment with the phorbol ester phorbol 12-myristate 13-acetate concomitantly reduced PKB activity, whereas stimulation of other PLC-coupled receptors also activated PKB; (ii) Ca2+ ionophores and thapsigargin stimulated PKB activity in a wortmannin-sensitive manner, whereas bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid blocked carbachol-stimulated PKB activity; (iii) phorbol 12-myristate 13-acetate alone did not activate PKB, whereas a protein kinase C inhibitor did not prevent the activation of PKB by carbachol; and (iv) carbachol stimulated ErbB3-tyrosine phosphorylation and association with p85, and both these and PKB activity were blocked by tyrphostin AG1478, an epidermal growth factor receptor-tyrosine kinase inhibitor. These experiments define a novel pathway linking G(q)-coupled G-protein-coupled receptors to the activation of PI 3-kinase and PKB.
    Original languageEnglish
    Pages (from-to)338-344
    Number of pages7
    JournalJournal of Biological Chemistry
    Volume277
    Issue number1
    DOIs
    Publication statusPublished - Jan 2002

    Keywords

    • 1-Phosphatidylinositol 3-Kinase physiology
    • Astrocytoma enzymology
    • Protein-serine-threonine kinases
    • Proto-oncogene proteins physiology
    • Receptor erbB-3 physiology
    • Receptors
    • Muscarinic physiology
    • Type C phospholipases physiology

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