G Protein-regulated Inducer of Neurite Outgrowth (GRIN) Modulates Sprouty Protein Repression of Mitogen-activated Protein Kinase (MAPK) Activation by Growth Factor Stimulation

• Published in: The Journal of biological chemistry 2012-04, Vol.287 (17), p.13674-13685
• Main Authors: Hwangpo, Tracy Anh, Jordan, J. Dedrick, Premsrirut, Prem K., Jayamaran, Gomathi, Licht, Jonathan D., Iyengar, Ravi, Neves, Susana R.
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Animals; Brain - metabolism; Cannabinoid Receptors; Carrier Proteins - metabolism; Cell Differentiation; Cell Line, Tumor; Cell Signaling; G Protein-coupled Receptors (GPCR); G Proteins; Gene Expression Regulation; Gene Library; HEK293 Cells; Humans; Intercellular Signaling Peptides and Proteins - metabolism; Intracellular Signaling Peptides and Proteins - metabolism; MAP Kinase Signaling System - physiology; MAP Kinases (MAPKs); Membrane Proteins - metabolism; Mice; Nerve Tissue Proteins - metabolism; Neurons - metabolism; Phosphorylation; Protein Structure, Tertiary; Protein-Serine-Threonine Kinases; Receptors, N-Methyl-D-Aspartate - metabolism; Signal Transduction; Tyrosine - chemistry
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.320705

Gαo/i interacts directly with GRIN (G protein-regulated inducer of neurite outgrowth). Using the yeast two-hybrid system, we identified Sprouty2 as an interacting partner of GRIN. Gαo and Sprouty2 bind to overlapping regions of GRIN, thus competing for GRIN binding. Imaging experiments demonstrated that Gαo expression promoted GRIN translocation to the plasma membrane, whereas Sprouty2 expression failed to do so. Given the role of Sprouty2 in the regulation of growth factor-mediated MAPK activation, we examined the contribution of the GRIN-Sprouty2 interaction to CB1 cannabinoid receptor regulation of FGF receptor signaling. In Neuro-2A cells, a system that expresses all of the components endogenously, modulation of GRIN levels led to regulation of MAPK activation. Overexpression of GRIN potentiated FGF activation of MAPK and decreased tyrosine phosphorylation of Sprouty2. Pretreatment with Go/i-coupled CB1 receptor agonist attenuated subsequent FGF activation of MAPK. Decreased expression of GRIN both diminished FGF activation of MAPK and blocked CB1R attenuation of MAPK activation. These observations indicate that Gαo interacts with GRIN and outcompetes GRIN from bound Sprouty. Free Sprouty then in turn inhibits growth factor signaling. Thus, here we present a novel mechanism of how Go/i-coupled receptors can inhibit growth factor signaling to MAPK. Background: GRIN is an effector of Go/i known to regulate neurite extension. Results: GRIN modulates MAPK by sequestering Sprouty, an inhibitor of the MAPK pathway, and this is reversed by active Gαo binding. Conclusion: Activation of Gαo can inhibit the MAPK pathway by releasing Sprouty from GRIN binding. Significance: This is a novel mechanism of GPCR regulation of the MAPK pathway.