Anchored protein kinase A recruitment of active Rac GTPase

J Biol Chem. 2011 Jun 24;286(25):22113-21. doi: 10.1074/jbc.M111.232660. Epub 2011 Apr 1.

Abstract

Protein kinase A-anchoring proteins (AKAPs) influence fundamental cellular processes by directing the cAMP-dependent protein kinase (PKA) toward its intended substrates. In this report we describe the identification and characterization of a ternary complex of AKAP220, the PKA holoenzyme, and the IQ domain GTPase-activating protein 2 isoform (IQGAP2) that is enriched at cortical regions of the cell. Formation of an IQGAP2-AKAP220 core complex initiates a subsequent phase of protein recruitment that includes the small GTPase Rac. Biochemical and molecular biology approaches reveal that PKA phosphorylation of Thr-716 on IQGAP2 enhances association with the active form of the Rac GTPase. Cell-based experiments indicate that overexpression of an IQGAP2 phosphomimetic mutant (IQGAP2 T716D) enhances the formation of actin-rich membrane ruffles at the periphery of HEK 293 cells. In contrast, expression of a nonphosphorylatable IQGAP2 T716A mutant or gene silencing of AKAP220 suppresses formation of membrane ruffles. These findings imply that IQGAP2 and AKAP220 act synergistically to sustain PKA-mediated recruitment of effectors such as Rac GTPases that impact the actin cytoskeleton.

Publication types

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

MeSH terms

  • A Kinase Anchor Proteins / chemistry
  • A Kinase Anchor Proteins / metabolism*
  • Actins / metabolism
  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Cytoskeleton / metabolism
  • HEK293 Cells
  • Humans
  • Mice
  • Molecular Sequence Data
  • Phosphorylation
  • Signal Transduction
  • rac GTP-Binding Proteins / metabolism*
  • ras GTPase-Activating Proteins / metabolism

Substances

  • A Kinase Anchor Proteins
  • Actins
  • Akap11 protein, mouse
  • IQGAP2 protein, human
  • ras GTPase-Activating Proteins
  • Cyclic AMP-Dependent Protein Kinases
  • rac GTP-Binding Proteins