Amplification of receptor signalling by Ca2+ entry-mediated translocation and activation of PLCgamma2 in B lymphocytes

EMBO J. 2003 Sep 15;22(18):4677-88. doi: 10.1093/emboj/cdg457.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • B-Lymphocytes / enzymology
  • B-Lymphocytes / physiology*
  • Calcium Signaling / physiology*
  • Chickens
  • DNA Primers
  • Enzyme Activation
  • Inositol 1,4,5-Trisphosphate / pharmacology
  • Kinetics
  • Mitogen-Activated Protein Kinases / metabolism
  • Models, Biological
  • Patch-Clamp Techniques
  • Phospholipase C gamma
  • Polymerase Chain Reaction
  • Protein Transport
  • Recombinant Fusion Proteins / metabolism
  • Sequence Deletion
  • Type C Phospholipases / genetics
  • Type C Phospholipases / metabolism*

Substances

  • DNA Primers
  • Recombinant Fusion Proteins
  • Inositol 1,4,5-Trisphosphate
  • Mitogen-Activated Protein Kinases
  • Type C Phospholipases
  • Phospholipase C gamma