In non-excitable cells, receptor-activated Ca2+ signalling comprises initial transient responses followed by a Ca2+ entry-dependent sustained and/or oscillatory phase. Here, we describe the molecular mechanism underlying the second phase linked to signal amplification. An in vivo inositol 1,4,5-trisphosphate (IP3) sensor revealed that in B lymphocytes, receptor-activated and store-operated Ca2+ entry greatly enhanced IP3 production, which terminated in phospholipase Cγ2 (PLCγ2)-deficient cells. Association between receptor-activated TRPC3 Ca2+ channels and PLCγ2, which cooperate in potentiating Ca2+ responses, was demonstrated by co-immunoprecipitation. PLCγ2-deficient cells displayed diminished Ca2+ entry-induced Ca2+ responses. However, this defect was canceled by suppressing IP3-induced Ca2+ release, implying that IP3 and IP3 receptors mediate the second Ca2+ phase. Furthermore, confocal visualization of PLCγ2 mutants demonstrated that Ca2+ entry evoked a C2 domain-mediated PLCγ2 translocation towards the plasma membrane in a lipase-independent manner to activate PLCγ2. Strikingly, Ca2+ entry-activated PLCγ2 maintained Ca2+ oscillation and extracellular signal-regulated kinase activation downstream of protein kinase C. We suggest that coupling of Ca2+ entry with PLCγ2 translocation and activation controls the amplification and co-ordination of receptor signalling
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