Spatial and Temporal Control of Cofilin Activity Is Required for Directional Sensing During Chemotaxis

Curr Biol. 2006 Nov 21;16(22):2193-205. doi: 10.1016/j.cub.2006.09.016.

Abstract

Background: Previous work has led to the hypothesis that cofilin severing, as regulated by PLC, is involved in chemotactic sensing. We have tested this hypothesis by investigating whether activation of endogenous cofilin is spatially and temporally linked to sensing an EGF point source in carcinoma cells.

Results: We demonstrate that inhibition of endogenous cofilin activity with either siRNA or overexpression of LIMK suppresses directional sensing in carcinoma cells. LIMK siRNA knockdown, which suppresses cofilin phosphorylation, and microinjection of S3C cofilin, a cofilin mutant that is constitutively active and not phosphorylated by LIMK, also inhibits directional sensing and chemotaxis. These results indicate that phosphorylation of cofilin by LIMK, in addition to cofilin activity, is required for chemotaxis. Cofilin activity concentrates rapidly at the newly formed leading edge facing the gradient, whereas cofilin phosphorylation increases throughout the cell. Quantification of these results indicates that the amplification of asymmetric actin polymerization required for protrusion toward the EGF gradient occurs at the level of cofilin but not at the level of PLC activation by EGFR.

Conclusions: These results indicate that local activation of cofilin by PLC and its global inactivation by LIMK phosphorylation combine to generate the local asymmetry of actin polymerization required for chemotaxis.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Actin Cytoskeleton / metabolism
  • Actin Depolymerizing Factors / genetics
  • Actin Depolymerizing Factors / metabolism*
  • Animals
  • Cell Line, Tumor
  • Cell Movement / physiology*
  • Chemotactic Factors / metabolism
  • Chemotaxis / drug effects
  • Chemotaxis / physiology*
  • Epidermal Growth Factor / metabolism
  • Epidermal Growth Factor / pharmacology
  • Lim Kinases
  • Phosphorylation
  • Protein Kinases / metabolism
  • Protein Kinases / pharmacology
  • RNA, Small Interfering / genetics
  • Rats
  • Type C Phospholipases / metabolism

Substances

  • Actin Depolymerizing Factors
  • Chemotactic Factors
  • RNA, Small Interfering
  • Epidermal Growth Factor
  • Protein Kinases
  • Lim Kinases
  • Limk1 protein, rat
  • Type C Phospholipases