Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin

Mol Biol Cell. 2014 Nov 5;25(22):3654-71. doi: 10.1091/mbc.E14-05-0978. Epub 2014 Sep 3.


A long-standing issue in the field of signal transduction is to understand the cross-talk between receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major and distinct signaling hubs that control eukaryotic cell behavior. Although stimulation of many RTKs leads to activation of trimeric G proteins, the molecular mechanisms behind this phenomenon remain elusive. We discovered a unifying mechanism that allows GIV/Girdin, a bona fide metastasis-related protein and a guanine-nucleotide exchange factor (GEF) for Gαi, to serve as a direct platform for multiple RTKs to activate Gαi proteins. Using a combination of homology modeling, protein-protein interaction, and kinase assays, we demonstrate that a stretch of ∼110 amino acids within GIV C-terminus displays structural plasticity that allows folding into a SH2-like domain in the presence of phosphotyrosine ligands. Using protein-protein interaction assays, we demonstrated that both SH2 and GEF domains of GIV are required for the formation of a ligand-activated ternary complex between GIV, Gαi, and growth factor receptors and for activation of Gαi after growth factor stimulation. Expression of a SH2-deficient GIV mutant (Arg 1745→Leu) that cannot bind RTKs impaired all previously demonstrated functions of GIV-Akt enhancement, actin remodeling, and cell migration. The mechanistic and structural insights gained here shed light on the long-standing questions surrounding RTK/G protein cross-talk, set a novel paradigm, and characterize a unique pharmacological target for uncoupling GIV-dependent signaling downstream of multiple oncogenic RTKs.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Movement
  • ErbB Receptors / chemistry*
  • ErbB Receptors / genetics
  • ErbB Receptors / metabolism
  • GTP-Binding Protein alpha Subunits, Gi-Go / chemistry*
  • GTP-Binding Protein alpha Subunits, Gi-Go / genetics
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism
  • Gene Expression Regulation
  • HeLa Cells
  • Humans
  • Microfilament Proteins / chemistry*
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Binding
  • Protein Folding
  • Protein Interaction Domains and Motifs
  • Signal Transduction
  • Structural Homology, Protein
  • Vesicular Transport Proteins / chemistry*
  • Vesicular Transport Proteins / genetics
  • Vesicular Transport Proteins / metabolism


  • CCDC88A protein, human
  • Microfilament Proteins
  • Vesicular Transport Proteins
  • EGFR protein, human
  • ErbB Receptors
  • GNAI3 protein, human
  • GTP-Binding Protein alpha Subunits, Gi-Go