Domain-domain interaction of P-Rex1 is essential for the activation and inhibition by G protein betagamma subunits and PKA

Cell Signal. 2008 Aug;20(8):1545-54. doi: 10.1016/j.cellsig.2008.04.009. Epub 2008 Apr 24.


PtdIns(3, 4, 5)P(3)-dependent Rac exchanger (P-Rex) 1 is a guanine nucleotide exchange factor (GEF) for the small GTPase Rac. P-Rex1 is activated by G protein betagamma subunits (Gbetagamma), and the Gbetagamma-induced activation is inhibited by cAMP-dependent protein kinase A (PKA). However, the details of regulatory mechanism of P-Rex1 remain to be clarified. In the present study, we investigated the mechanism of activation and inhibition of P-Rex1 using various truncated and alanine-substituted mutants and found that the domain-domain interaction of P-Rex1 is important for Gbetagamma-induced activation and PKA-induced inhibition. Immunoprecipitation analysis showed that the second Disheveled/EGL-10/Pleckstrin (DEP) and first PSD-95/Dlg/ZO-1 (PDZ) domains of P-Rex1 associate with the inositol polyphosphate-4-phosphatase (IP4P) domain. Carboxyl-terminal truncation on the IP4P domain or mutations in the protein-binding pocket of the first PDZ domain abolished the association. Analysis of in vitro guanine nucleotide exchange assay, PAK1/2 phosphorylation, and Rac-specific actin reorganization revealed that Gbetagamma could activate a complex of the P-Rex1 mutant lacking the IP4P domain and the isolated IP4P domain as well as full-length P-Rex1. Moreover, PKA phosphorylation prevented the domain-domain interaction and Gbetagamma-binding. These results provide a new insight into the regulation of other Rho-family GEFs and cell responses induced by the heterotrimeric G protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / ultrastructure
  • Animals
  • Cell Line
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • GTP-Binding Protein beta Subunits / metabolism*
  • GTP-Binding Protein gamma Subunits / metabolism*
  • Guanine Nucleotide Exchange Factors / chemistry*
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Humans
  • Mice
  • Protein Interaction Domains and Motifs


  • G-protein Beta gamma
  • GTP-Binding Protein beta Subunits
  • GTP-Binding Protein gamma Subunits
  • Guanine Nucleotide Exchange Factors
  • PREX1 protein, mouse
  • Cyclic AMP-Dependent Protein Kinases