| First Author | Pradhan S | Year | 2017 |
| Journal | J Biol Chem | Volume | 292 |
| Issue | 32 | Pages | 13133-13142 |
| PubMed ID | 28615442 | Mgi Jnum | J:346365 |
| Mgi Id | MGI:6869681 | Doi | 10.1074/jbc.M117.796656 |
| Citation | Pradhan S, et al. (2017) The heterotrimeric G protein Gbeta1 interacts with the catalytic subunit of protein phosphatase 1 and modulates G protein-coupled receptor signaling in platelets. J Biol Chem 292(32):13133-13142 |
| abstractText | Thrombosis is caused by the activation of platelets at the site of ruptured atherosclerotic plaques. This activation involves engagement of G protein-coupled receptors (GPCR) on platelets that promote their aggregation. Although it is known that protein kinases and phosphatases modulate GPCR signaling, how serine/threonine phosphatases integrate with G protein signaling pathways is less understood. Because the subcellular localization and substrate specificity of the catalytic subunit of protein phosphatase 1 (PP1c) is dictated by PP1c-interacting proteins, here we sought to identify new PP1c interactors. GPCRs signal via the canonical heterotrimeric Galpha and Gbetagamma subunits. Using a yeast two-hybrid screen, we discovered an interaction between PP1calpha and the heterotrimeric G protein Gbeta1 subunit. Co-immunoprecipitation studies with epitope-tagged PP1c and Gbeta1 revealed that Gbeta1 interacts with the PP1c alpha, beta, and gamma1 isoforms. Purified PP1c bound to recombinant Gbeta1-GST protein, and PP1c co-immunoprecipitated with Gbeta1 in unstimulated platelets. Thrombin stimulation of platelets induced the dissociation of the PP1c-Gbeta1 complex, which correlated with an association of PP1c with phospholipase C beta3 (PLCbeta3), along with a concomitant dephosphorylation of the inhibitory Ser(1105) residue in PLCbeta3. siRNA-mediated depletion of GNB1 (encoding Gbeta1) in murine megakaryocytes reduced protease-activated receptor 4, activating peptide-induced soluble fibrinogen binding. Thrombin-induced aggregation was decreased in PP1calpha(-/-) murine platelets and in human platelets treated with a small-molecule inhibitor of Gbetagamma. Finally, disruption of PP1c-Gbeta1 complexes with myristoylated Gbeta1 peptides containing the PP1c binding site moderately decreased thrombin-induced human platelet aggregation. These findings suggest that Gbeta1 protein enlists PP1c to modulate GPCR signaling in platelets. |
