Galphaq directly activates p63RhoGEF and Trio via a conserved extension of the Dbl homology-associated pleckstrin homology domain

J Biol Chem. 2007 Oct 5;282(40):29201-10. doi: 10.1074/jbc.M703458200. Epub 2007 Jul 2.

Abstract

The coordinated cross-talk from heterotrimeric G proteins to Rho GTPases is essential during a variety of physiological processes. Emerging data suggest that members of the Galpha(12/13) and Galpha(q/11) families of heterotrimeric G proteins signal downstream to RhoA via distinct pathways. Although studies have elucidated mechanisms governing Galpha(12/13)-mediated RhoA activation, proteins that functionally couple Galpha(q/11) to RhoA activation have remained elusive. Recently, the Dbl-family guanine nucleotide exchange factor (GEF) p63RhoGEF/GEFT has been described as a novel mediator of Galpha(q/11) signaling to RhoA based on its ability to synergize with Galpha(q/11) resulting in enhanced RhoA signaling in cells. We have used biochemical/biophysical approaches with purified protein components to better understand the mechanism by which activated Galpha(q) directly engages and stimulates p63RhoGEF. Basally, p63RhoGEF is autoinhibited by the Dbl homology (DH)-associated pleckstrin homology (PH) domain; activated Galpha(q) relieves this autoinhibition by interacting with a highly conserved C-terminal extension of the PH domain. This unique extension is conserved in the related Dbl-family members Trio and Kalirin and we show that the C-terminal Rho-specific DH-PH cassette of Trio is similarly activated by Galpha(q).

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Biochemistry / methods
  • Biophysics / methods
  • Dimerization
  • GTP-Binding Protein alpha Subunits, Gq-G11 / chemistry*
  • GTP-Binding Protein alpha Subunits, Gq-G11 / metabolism
  • Guanine Nucleotide Exchange Factors / chemistry
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Molecular Sequence Data
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / chemistry
  • Proto-Oncogene Proteins / metabolism*
  • Rho Guanine Nucleotide Exchange Factors
  • Sequence Homology, Amino Acid
  • Signal Transduction

Substances

  • ARHGEF25 protein, human
  • Guanine Nucleotide Exchange Factors
  • MCF2 protein, human
  • Proto-Oncogene Proteins
  • Rho Guanine Nucleotide Exchange Factors
  • Protein-Serine-Threonine Kinases
  • TRIO protein, human
  • GTP-Binding Protein alpha Subunits, Gq-G11