Activation of RasGRP3 by phosphorylation of Thr-133 is required for B cell receptor-mediated Ras activation

Proc Natl Acad Sci U S A. 2004 Nov 23;101(47):16612-7. doi: 10.1073/pnas.0407468101. Epub 2004 Nov 15.


The Ras signaling pathway plays a critical role in B lymphocyte development and activation, but its activation mechanism has not been well understood. At least one mode of Ras regulation in B cells involves a Ras-guanyl nucleotide exchange factor, RasGRP3. We demonstrate here that RasGRP3 undergoes phosphorylation at Thr-133 upon B cell receptor cross-linking, thereby resulting in its activation. Deletion of phospholipase C-gamma2 or pharmacological interference with conventional PKCs resulted in marked reduction in both Thr-133 phosphorylation and Ras activation. Moreover, mutation of Thr-133 in RasGRP3 alone severely impaired its ability to activate Ras in B cell receptor signaling. Hence, our data suggest that PKC, after being activated by diacylglycerol, phosphorylates RasGRP3, thereby contributing to its full activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Chickens
  • Cross-Linking Reagents
  • Guanine Nucleotide Exchange Factors / chemistry*
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Humans
  • Models, Molecular
  • Mutation
  • Phospholipase C gamma
  • Phosphorylation
  • Protein Conformation
  • Protein Kinase C / metabolism
  • Receptors, Antigen, B-Cell / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Static Electricity
  • Threonine / chemistry
  • Type C Phospholipases / metabolism
  • ras Proteins / metabolism*


  • Cross-Linking Reagents
  • Guanine Nucleotide Exchange Factors
  • Receptors, Antigen, B-Cell
  • Recombinant Proteins
  • Threonine
  • Protein Kinase C
  • Type C Phospholipases
  • Phospholipase C gamma
  • ras Proteins