The small GTP-binding protein rac regulates growth factor-induced membrane ruffling

Cell. 1992 Aug 7;70(3):401-10. doi: 10.1016/0092-8674(92)90164-8.


The function of rac, a ras-related GTP-binding protein, was investigated in fibroblasts by microinjection. In confluent serum-starved Swiss 3T3 cells, rac1 rapidly stimulated actin filament accumulation at the plasma membrane, forming membrane ruffles. Several growth factors and activated H-ras also induced membrane ruffling, and this response was prevented by a dominant inhibitory mutant rac protein, N17rac1. This suggests that endogenous rac proteins are required for growth factor-induced membrane ruffling. In addition to membrane ruffling, a later response to both rac1 microinjection and some growth factors was the formation of actin stress fibers, a process requiring endogenous rho proteins. Using N17rac1 we have shown that these growth factors act through rac to stimulate this rho-dependent response. We propose that rac and rho are essential components of signal transduction pathways linking growth factors to the organization of polymerized actin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Actins / metabolism*
  • Animals
  • Cell Adhesion / physiology
  • Cell Membrane / physiology*
  • Culture Media, Serum-Free
  • Cytoskeleton / metabolism
  • Fluorescent Antibody Technique
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / physiology*
  • Growth Substances / physiology*
  • Guanosine Diphosphate / metabolism
  • Guanosine Triphosphate / metabolism
  • Mice
  • Oncogene Protein p21(ras) / antagonists & inhibitors
  • Oncogene Protein p21(ras) / physiology
  • Pinocytosis
  • Substrate Specificity
  • rac GTP-Binding Proteins


  • Actins
  • Culture Media, Serum-Free
  • Growth Substances
  • Guanosine Diphosphate
  • Guanosine Triphosphate
  • GTP-Binding Proteins
  • Oncogene Protein p21(ras)
  • rac GTP-Binding Proteins