The exocyst complex regulates insulin-stimulated glucose uptake of skeletal muscle cells

Author:

Fujimoto Brent A.1ORCID,Young Madison1,Carter Lamar1,Pang Alina P. S.2,Corley Michael J.2,Fogelgren Ben1,Polgar Noemi1

Affiliation:

1. Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii

2. Department of Native Hawaiian Health, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii

Abstract

Skeletal muscle handles ~80–90% of the insulin-induced glucose uptake. In skeletal muscle, insulin binding to its cell surface receptor triggers redistribution of intracellular glucose transporter GLUT4 protein to the cell surface, enabling facilitated glucose uptake. In adipocytes, the eight-protein exocyst complex is an indispensable constituent in insulin-induced glucose uptake, as it is responsible for the targeted trafficking and plasma membrane-delivery of GLUT4. However, the role of the exocyst in skeletal muscle glucose uptake has never been investigated. Here we demonstrate that the exocyst is a necessary factor in insulin-induced glucose uptake in skeletal muscle cells as well. The exocyst complex colocalizes with GLUT4 storage vesicles in L6-GLUT4myc myoblasts at a basal state and associates with these vesicles during their translocation to the plasma membrane after insulin signaling. Moreover, we show that the exocyst inhibitor endosidin-2 and a heterozygous knockout of Exoc5 in skeletal myoblast cells both lead to impaired GLUT4 trafficking to the plasma membrane and hinder glucose uptake in response to an insulin stimulus. Our research is the first to establish that the exocyst complex regulates insulin-induced GLUT4 exocytosis and glucose metabolism in muscle cells. A deeper knowledge of the role of the exocyst complex in skeletal muscle tissue may help our understanding of insulin resistance in type 2 diabetes.

Funder

HHS | NIH | National Institute of General Medical Sciences

HHS | NIH | National Institute of Diabetes and Digestive and Kidney Diseases

HHS | NIH | National Institute on Minority Health and Health Disparities

HHS | NIH | National Heart, Lung, and Blood Institute

Publisher

American Physiological Society

Subject

Physiology (medical),Physiology,Endocrinology, Diabetes and Metabolism

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