title: Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin.
abstract: 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.
authors.affiliation: Department of Medicine, University of California, San Diego, School of Medicine, CA 92093.
authors.forename: Changsheng
authors.initials: C
authors.lastname: Lin
authors.affiliation: Department of Medicine, University of California, San Diego, School of Medicine, CA 92093.
authors.forename: Jason
authors.initials: J
authors.lastname: Ear
authors.affiliation: Department of Medicine, University of California, San Diego, School of Medicine, CA 92093.
authors.forename: Krishna
authors.initials: K
authors.lastname: Midde
authors.affiliation: Department of Medicine, University of California, San Diego, School of Medicine, CA 92093.
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Lopez-Sanchez
authors.affiliation: Department of Medicine, University of California, San Diego, School of Medicine, CA 92093.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Aznar
authors.affiliation: Department of Cellular and Molecular Medicine, University of California, San Diego, School of Medicine, CA 92093.
authors.forename: Mikel
authors.initials: M
authors.lastname: Garcia-Marcos
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Irina
authors.initials: I
authors.lastname: Kufareva
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Ruben
authors.initials: R
authors.lastname: Abagyan
authors.affiliation: Department of Medicine, University of California, San Diego, School of Medicine, CA 92093 prghosh@ucsd.edu.
authors.forename: Pradipta
authors.initials: P
authors.lastname: Ghosh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002465:Cell Movement; D066246:ErbB Receptors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017510:Protein Folding; D054730:Protein Interaction Domains and Motifs; D015398:Signal Transduction; D040681:Structural Homology, Protein; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C502451:CCDC88A protein, human; D008840:Microfilament Proteins; D033921:Vesicular Transport Proteins; C512478:EGFR protein, human; D066246:ErbB Receptors; C498819:GNAI3 protein, human; D019206:GTP-Binding Protein alpha Subunits, Gi-Go