The Phosphatidylinositol (3,4,5)-Trisphosphate-dependent Rac Exchanger 1·Ras-related C3 Botulinum Toxin Substrate 1 (P-Rex1·Rac1) Complex Reveals the Basis of Rac1 Activation in Breast Cancer Cells

J Biol Chem. 2015 Aug 21;290(34):20827-20840. doi: 10.1074/jbc.M115.660456. Epub 2015 Jun 24.


The P-Rex (phosphatidylinositol (3,4,5)-trisphosphate (PIP3)-dependent Rac exchanger) family (P-Rex1 and P-Rex2) of the Rho guanine nucleotide exchange factors (Rho GEFs) activate Rac GTPases to regulate cell migration, invasion, and metastasis in several human cancers. The family is unique among Rho GEFs, as their activity is regulated by the synergistic binding of PIP3 and Gβγ at the plasma membrane. However, the molecular mechanism of this family of multi-domain proteins remains unclear. We report the 1.95 Å crystal structure of the catalytic P-Rex1 DH-PH tandem domain in complex with its cognate GTPase, Rac1 (Ras-related C3 botulinum toxin substrate-1). Mutations in the P-Rex1·Rac1 interface revealed a critical role for this complex in signaling downstream of receptor tyrosine kinases and G protein-coupled receptors. The structural data indicated that the PIP3/Gβγ binding sites are on the opposite surface and markedly removed from the Rac1 interface, supporting a model whereby P-Rex1 binding to PIP3 and/or Gβγ releases inhibitory C-terminal domains to expose the Rac1 binding site.

Keywords: G protein-coupled receptor (GPCR); P-Rex1; PREX1; PREX2; Ras-related C3 botulinum toxin substrate 1 (Rac1); Rho (Rho GTPase); breast cancer; crystallography; guanine nucleotide exchange factor (GEF); receptor tyrosine kinase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Baculoviridae / genetics
  • Catalytic Domain
  • Crystallography, X-Ray
  • Enzyme Activation
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Guanine Nucleotide Exchange Factors / chemistry*
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism
  • Humans
  • MCF-7 Cells
  • Models, Molecular
  • Molecular Sequence Data
  • Mutation
  • Phosphatidylinositol Phosphates / chemistry*
  • Phosphatidylinositol Phosphates / metabolism
  • Protein Binding
  • Recombinant Fusion Proteins / chemistry*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sequence Alignment
  • Sf9 Cells
  • Signal Transduction
  • Spodoptera
  • rac1 GTP-Binding Protein / chemistry*
  • rac1 GTP-Binding Protein / genetics
  • rac1 GTP-Binding Protein / metabolism


  • Guanine Nucleotide Exchange Factors
  • PREX1 protein, human
  • Phosphatidylinositol Phosphates
  • RAC1 protein, human
  • Recombinant Fusion Proteins
  • phosphatidylinositol 3,4,5-triphosphate
  • rac1 GTP-Binding Protein

Associated data

  • PDB/1I4D
  • PDB/1OMW
  • PDB/2DFK
  • PDB/3LJU
  • PDB/3SBD
  • PDB/4YON