P-Rex1 Mediates Glucose-Stimulated Rac1 Activation and Insulin Secretion in Pancreatic β-Cells

Overview

Journal Cell Physiol Biochem

Specialties Biochemistry
Cell Biology
Pharmacology

Date 2020 Dec 21

PMID 33347743

Citations 10

Authors

Vijayalakshmi Thamilselvan

Suhadinie Gamage

Ali Harajli

Sri Aneesha Chundru

Anjaneyulu Kowluru

Affiliations

Soon will be listed here.

Abstract

Background/aims: Despite the published evidence implicating phosphoinositide 3-kinase (PI3-kinase) in the regulation of islet function, limited information is available on the putative contributory roles of its downstream signaling steps, including the phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 1 (P-Rex1) signaling pathway in the islet β-cell. Therefore, we investigated potential roles for P-Rex1 in glucose-stimulated Rac1 activation and insulin secretion in insulin-secreting (INS-1 832/13) β-cells.

Methods: Glucose-stimulated Insulin secretion (GSIS) was quantified by ELISA. Expression of endogenous P-Rex1 and RhoG was suppressed by siRNA transfection using the DharmaFect1 reagent. Total membrane and cytosolic fractions were isolated using the Mem-PER Plus Membrane Extraction Kit. The degree of activation of Rac1 was determined by the pull-down assay.

Results: P-Rex1 is expressed in INS-1 832/13 cells, normal rat islets and human islets. siRNA-mediated knockdown of P-Rex1 attenuated glucose-induced Rac1 activation, membrane association and insulin secretion. RhoG, which has been implicated in PI3-kinase-mediated Rac1 activation in other cell types, appears not to contribute to GSIS since the siRNA-mediated knockdown of RhoG failed to exert significant effects on GSIS. LY294002, a known inhibitor of PI3-kinase, potentiated GSIS without affecting glucose-induced Rac1 activation.

Conclusion: Based on these findings, we conclude that P-Rex1 plays a novel regulatory role in glucose-induced Rac1 activation and insulin secretion.

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