Identification of RhoGAP22 as an Akt-dependent regulator of cell motility in response to insulin

Mol Cell Biol. 2011 Dec;31(23):4789-800. doi: 10.1128/MCB.05583-11. Epub 2011 Oct 3.

Abstract

Insulin exerts many of its metabolic actions via the canonical phosphatidylinositide 3 kinase (PI3K)/Akt pathway, leading to phosphorylation and 14-3-3 binding of key metabolic targets. We previously identified a GTPase-activating protein (GAP) for Rac1 called RhoGAP22 as an insulin-responsive 14-3-3 binding protein. Insulin increased 14-3-3 binding to RhoGAP22 fourfold, and this effect was PI3K dependent. We identified two insulin-responsive 14-3-3 binding sites (pSer(16) and pSer(395)) within RhoGAP22, and mutagenesis studies revealed a complex interplay between the phosphorylation at these two sites. Mutating Ser(16) to alanine blocked 14-3-3 binding to RhoGAP22 in vivo, and phosphorylation at Ser(16) was mediated by the kinase Akt. Overexpression of a mutant RhoGAP22 that was unable to bind 14-3-3 reduced cell motility in NIH-3T3 fibroblasts, and this effect was dependent on a functional GAP domain. Mutation of the catalytic arginine of the GAP domain of RhoGAP22 potentiated growth factor-stimulated Rac1 GTP loading. We propose that insulin and possibly growth factors such as platelet-derived growth factor may play a novel role in regulating cell migration and motility via the Akt-dependent phosphorylation of RhoGAP22, leading to modulation of Rac1 activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins / metabolism
  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • Binding Sites
  • Catalytic Domain
  • Cell Line
  • Cell Movement*
  • Conserved Sequence
  • Cricetinae
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism*
  • Gene Knockdown Techniques
  • Humans
  • Insulin / pharmacology
  • Insulin / physiology*
  • Mice
  • Molecular Sequence Data
  • Phosphorylation
  • Protein Binding
  • Protein Structure, Tertiary
  • Proto-Oncogene Proteins c-akt / metabolism*
  • RNA Interference
  • Rats

Substances

  • 14-3-3 Proteins
  • GTPase-Activating Proteins
  • Insulin
  • RhoGAP22 protein, human
  • Proto-Oncogene Proteins c-akt