Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin.
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.
Mesh Terms:
Amino Acid Sequence, Animals, Cell Movement, ErbB Receptors, GTP-Binding Protein alpha Subunits, Gi-Go, Gene Expression Regulation, HeLa Cells, Humans, Microfilament Proteins, Models, Molecular, Molecular Sequence Data, Protein Binding, Protein Folding, Protein Interaction Domains and Motifs, Signal Transduction, Structural Homology, Protein, Vesicular Transport Proteins
Amino Acid Sequence, Animals, Cell Movement, ErbB Receptors, GTP-Binding Protein alpha Subunits, Gi-Go, Gene Expression Regulation, HeLa Cells, Humans, Microfilament Proteins, Models, Molecular, Molecular Sequence Data, Protein Binding, Protein Folding, Protein Interaction Domains and Motifs, Signal Transduction, Structural Homology, Protein, Vesicular Transport Proteins
Mol. Biol. Cell
Date: Nov. 05, 2014
PubMed ID: 25187647
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