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Regulator of G protein signaling complex, Gβ5‐R7, promotes glucose‐ and extracellular signal‐stimulated insulin secretion
Author(s) -
Slepak Vladlen,
Wang Qiang,
Henry Taylor,
Pronin Alexey,
Lubaczeuski Camila,
Jang Geeng-Fu,
Crabb John,
Bernal-Misrachi Ernesto
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.02604
Subject(s) - medicine , g protein coupled receptor , endocrinology , insulin , glucose homeostasis , biology , knockout mouse , microbiology and biotechnology , regulator of g protein signaling , signal transduction , g protein , chemistry , receptor , gtpase activating protein , biochemistry , insulin resistance
Glucose‐stimulated insulin secretion (GSIS) is essential for maintaining energy homeostasis. G protein‐coupled receptors (GPCRs) are important modulators of this process by extracellular signals such as hormones, neurotransmitters and non‐glucose metabolites. We investigated the role of Gβ5‐R7, the protein complex consisting of the atypical G protein β subunit Gβ5 and a regulator of G protein signaling (RGS) of the R7 family. To analyze the effects of Gnb5 knockout on insulin secretion we used mouse insulinoma MIN6 cell line and pancreatic islets isolated from the Gnb5 −/− mice. Consistent with previous work, Gnb5 knockout diminished insulin secretion evoked by cholinergic agonist Oxo‐M. Here, we found that Gnb5 knockout also attenuated activity of other GPCR agonists ADP, AVP, GLP‐1, forskolin and, surprisingly, the response to high glucose. Our experiments also provided evidence that Gnb5 knockout eliminated the positive effect of cell adhesion on Oxo‐M‐stimulated GSIS, likely through adhesion GPCR GPR56. Total insulin content and the amount of insulin released in response to K+‐evoked membrane depolarization in Gnb5 − / − islets or MIN6 cells was normal. The pleiotropic effect on several GPCRs led us to the hypothesis that Gβ5‐R7 may play a non‐canonical role in insulin secretory pathway downstream of G protein signaling and glucose‐activated membrane depolarization. We found that Gnb5 knockout does not influence cortical actin depolymerization, but influences activity of protein kinase C, and thus far identified 14‐3‐3ɛ as one of the affected substrates. Together, these results allow us to propose that the Gβ5‐R7 complex regulates a phosphorylation event participating in the vesicular trafficking pathway, downstream of G protein signaling and actin depolymerization, but upstream of insulin granule release. Support or Funding Information This work was supported by National Institutes of Health Grants R01DK1054127(to V.S.), RO1‐DK073716, DK084236 (to E.B.M), EY11373 (to J.C.).