title: Amplification of receptor signalling by Ca2+ entry-mediated translocation and activation of PLCgamma2 in B lymphocytes.
abstract: 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 Cgamma2 (PLCgamma2)-deficient cells. Association between receptor-activated TRPC3 Ca2+ channels and PLCgamma2, which cooperate in potentiating Ca2+ responses, was demonstrated by co-immunoprecipitation. PLCgamma2-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 PLCgamma2 mutants demonstrated that Ca2+ entry evoked a C2 domain-mediated PLCgamma2 translocation towards the plasma membrane in a lipase-independent manner to activate PLCgamma2. Strikingly, Ca2+ entry-activated PLCgamma2 maintained Ca2+ oscillation and extracellular signal-regulated kinase activation downstream of protein kinase C. We suggest that coupling of Ca2+ entry with PLCgamma2 translocation and activation controls the amplification and co-ordination of receptor signalling.
authors.affiliation: Division of Molecular and Cellular Physiology, Center for Integrative Bioscience, Okazaki National Research Institutes, Okazaki, Aichi 444-8585, Japan.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Nishida
authors.forename: Kenji
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hara
authors.forename: Emiko
authors.initials: E
authors.lastname: Mori
authors.forename: Takashi
authors.initials: T
authors.lastname: Morii
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kurosaki
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mori
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002645:Chickens; D017931:DNA Primers; D004789:Enzyme Activation; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007700:Kinetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D018408:Patch-Clamp Techniques; D051966:Phospholipase C gamma; D016133:Polymerase Chain Reaction; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D011993:Recombinant Fusion Proteins; D015544:Inositol 1,4,5-Trisphosphate; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma