Phospholipase C gamma negatively regulates Rac/Cdc42 activation in antigen-stimulated mast cells

Eur J Immunol. 2007 Jan;37(1):261-70. doi: 10.1002/eji.200635875.


The Rho GTPases Rac and Cdc42 play a central role in the regulation of secretory and cytoskeletal responses in antigen-stimulated mast cells. In this study, we examine the kinetics and mechanism of Rac and Cdc42 activation in the rat basophilic leukemia RBL-2H3 cells. The activation kinetics of both Rac and Cdc42 show a biphasic profile, consisting of an early transient peak at 1 min and a late sustained activation phase at 20-40 min. The inhibition of phospholipase C (PLC)gamma causes a twofold increase in Rac and Cdc42 activation that coincides with a dramatic production of atypical filopodia-like structures. Inhibition of protein kinase C using bisindolylmaleimide mimics the effect of PLCgamma inhibition on Rac activation, but not on Cdc42 activation. In contrast, depletion of intracellular calcium leads to a complete inhibition of the early activation peak of both Rac and Cdc42, without significant effects on the late sustained activation. These data suggest that PLCgamma is involved in a negative feedback loop that leads to the inhibition of Rac and Cdc42. They also suggest that the presence of intracellular calcium is a prerequisite for both Rac and Cdc42 activation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens / physiology*
  • Calcium / physiology
  • Cell Line, Tumor
  • Down-Regulation / immunology*
  • Enzyme Activation / drug effects
  • Enzyme Activation / immunology
  • Enzyme Inhibitors / pharmacology
  • Estrenes / pharmacology
  • Exocytosis / immunology
  • Mast Cells / drug effects
  • Mast Cells / enzymology*
  • Mast Cells / immunology*
  • Phospholipase C gamma / antagonists & inhibitors
  • Phospholipase C gamma / physiology*
  • Pyrrolidinones / pharmacology
  • Rats
  • Up-Regulation / immunology
  • cdc42 GTP-Binding Protein / antagonists & inhibitors*
  • cdc42 GTP-Binding Protein / metabolism
  • rac GTP-Binding Proteins / antagonists & inhibitors*
  • rac GTP-Binding Proteins / metabolism


  • Antigens
  • Enzyme Inhibitors
  • Estrenes
  • Pyrrolidinones
  • 1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
  • Phospholipase C gamma
  • cdc42 GTP-Binding Protein
  • rac GTP-Binding Proteins
  • Calcium