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The Glucose Transporter 2 Undergoes Plasma Membrane Endocytosis and Lysosomal Degradation in a Secretagogue-Dependent Manner

North General Hospital (J.C.H.), New York, New York 10035; Institut de Biologie de Lille (J.V.), 59021 Lille Cedex, France; Departments of Medicine and Molecular Pharmacology (D.W., J.E.P.), Albert Einstein College of Medicine, Bronx New York 10461

Address all correspondence and requests for reprints to: Jeffrey E. Pessin, Department of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461. E-mail: jpessin{at}aecom.yu.edu.

In β-cells of the pancreas, the glucose transporter (GLUT)-2 facilitative glucose transporter protein is localized to the plasma membrane and functions as part of the glucose sensing mechanism for the stimulation of insulin secretion. We observed that expressed GLUT2 protein in the cultured Min6B1 cell line undergoes enhanced endocytosis at high extracellular glucose concentrations that stimulate insulin secretion. Moreover, the internalized GLUT2 protein undergoes rapid degradation induced by chronic high-glucose or arginine stimulation but does not undergo plasma membrane recycling or accumulation in any microscopically apparent intracellular membrane compartment. The rapid degradation of GLUT2 was prevented by lysosomal inhibition (chloroquine) concomitant with the accumulation of GLUT2 in endomembrane structures. In contrast, neither endocytosis nor the lack of internal membrane localized GLUT2 remained completely unaffected by proteosomal inhibition (lactacystin) or an heat shock protein-90 inhibitor (geldanamycin). Moreover, the endocytosis and degradation of GLUT2 was specific for β-cells because expression of GLUT2 in 3T3L1 adipocytes remained cell surface localized and did not display a rapid rate of degradation. Together, these data demonstrate that hyperglycemia directly affects β-cell function and activates a trafficking pathway that results in the rapid endocytosis and degradation of the cell surface GLUT2 glucose transporter.