Targeting of calcium:calmodulin signals to the cytoskeleton by IQGAP1

Cell Calcium. 2007 Jun;41(6):593-605. doi: 10.1016/j.ceca.2006.10.009. Epub 2006 Nov 29.


Mast cells reorganize their actin cytoskeleton in response to cytosolic calcium signals while in parallel secreting histamine and other inflammatory mediators. The effect of calcium on actin is mediated in large part through calmodulin. EGFP-tagged calmodulin is concentrated in the actin-rich cortex of RBL-2H3 mast cells. Transfection with small interfering RNA directed against the actin and calmodulin-binding protein IQGAP1 dramatically reduced expression of the latter protein and reduced or eliminated the concentration of calmodulin at the actin-rich cortex. Both actin reorganization and secretion were enhanced in IQGAP1 knockdown cells. Our results suggest a model in which calmodulin is targeted to and sequestered at the actin cytoskeleton by IQGAP1. Upon cell stimulation and the subsequent [Ca2+]i increase, it is immediately available to activate local downstream targets.

Publication types

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

MeSH terms

  • Animals
  • Calcium / metabolism
  • Calcium Signaling*
  • Calmodulin / metabolism*
  • Cell Line, Tumor
  • Cytoskeleton / metabolism*
  • Immunoblotting
  • Mast Cells / metabolism*
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Rats
  • ras GTPase-Activating Proteins / genetics
  • ras GTPase-Activating Proteins / metabolism*


  • Calmodulin
  • IQ motif containing GTPase activating protein 1
  • ras GTPase-Activating Proteins
  • Calcium