A Gi–GIV Molecular Complex Binds Epidermal Growth Factor Receptor and Determines Whether Cells Migrate or Proliferate

Pradipta Ghosh^*,, Anthony O. Beas^*, Scott J. Bornheimer^*, Mikel Garcia-Marcos^*, Erin P. Forry^*, Carola Johannson^*, Jason Ear, Barbara H. Jung, Betty Cabrera, John M. Carethers, and Marilyn G. Farquhar^*

Departments of *Cellular and Molecular Medicine and Medicine, School of Medicine, University of California–San Diego, La Jolla, CA 92093

Monitoring Editor: J. Silvio Gutkind

Abstract: Cells respond to growth factors by either migrating or proliferating, but not both at the same time, a phenomenon termed migration-proliferation dichotomy. The underlying mechanism of this phenomenon has remained unknown. We demonstrate here that G_i protein and GIV, its nonreceptor guanine nucleotide exchange factor (GEF), program EGF receptor (EGFR) signaling and orchestrate this dichotomy. GIV directly interacts with EGFR, and when its GEF function is intact, a G_i–GIV–EGFR signaling complex assembles, EGFR autophosphorylation is enhanced, and the receptor's association with the plasma membrane (PM) is prolonged. Accordingly, PM-based motogenic signals (PI3-kinase-Akt and PLC1) are amplified, and cell migration is triggered. In cells expressing a GEF-deficient mutant, the Gi–GIV-EGFR signaling complex is not assembled, EGFR autophosphorylation is reduced, the receptor's association with endosomes is prolonged, mitogenic signals (ERK 1/2, Src, and STAT5) are amplified, and cell proliferation is triggered. In rapidly growing, poorly motile breast and colon cancer cells and in noninvasive colorectal carcinomas in situ in which EGFR signaling favors mitosis over motility, a GEF-deficient splice variant of GIV was identified. In slow growing, highly motile cancer cells and late invasive carcinomas, GIV is highly expressed and has an intact GEF motif. Thus, inclusion or exclusion of GIV's GEF motif, which activates Gi, modulates EGFR signaling, generates migration-proliferation dichotomy, and most likely influences cancer progression.

Address correspondence to: Marilyn G. Farquhar (mfarquhar{at}ucsd.edu) or Pradipta Ghosh (prghosh{at}ucsd.edu).

Abbreviations: EGFR, Epidermal Growth Factor Receptor • GEF, Guanine nucleotide Exchange Factor • PI3K, Phosphoinositide 3-kinase • PLC, Phospholipase C • SH2, Src Homology 2 • ERK, Extracellular signal-Regulated Kinase • STAT5, Signal Transduced and Activator of Transcription 5 • VEGF, Vascular Endothelial Growth Factor • PDGF, Platelet-Derived Growth Factor • MAPK, Mitogen Activated Protein Kinase • HRP, Horseradish Peroxidase • EEA1, Early Endosome Antigen 1 • PM, Plasma Membrane • GBD, G protein Binding Domain • GAPDH, Glyceraldehyde 3-phosphate dehydrogenase • YFP, yellow fluorescent protein.

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