GSBS Dissertations and Theses

Title

Metabolic Regulation of Glucose Transport is an Insulin-Dependent Mechanism: A Dissertation

Approval Date

5-1-1993

Document Type

Doctoral Dissertation

Department

Graduate School of Biomedical Sciences, Biochemistry and Molecular Biology

Subjects

Glucose; Erythrocytes; Glucose Transporter Type 1; Biological Transport; Columbidae; Academic Dissertations; Dissertations, UMMS

Abstract

Protein-mediated sugar transport is nominally absent in normoxic (adequately oxygenated) pigeon erythrocytes. Following exposure to metabolic inhibitors (cyanide or carbonylcyanide-p-trifluoromethoxyphenylhydrazone), pigeon red cells transport sugars by a saturable, stereoselective pathway that is inhibited by cytochalasin B or forskolin. The sugar transport capacity of fully poisoned cells is consistent with a transporter density of approximately 30 carriers per erythrocyte. Immunoblot analyses and competition ELISA indicate that pigeon red cells contain approximately 200 copies of an integral plasma membrane protein immunologically related to the glucose transporter isoform GLUT1. GLUT1 is quantitatively restricted to the plasma membrane at all times. Pigeon red cells and brain lack proteins immunologically related to the sugar transporter isoforms GLUT3 and GLUT4. Specific immunodepletion of red cell GLUT1 content results in the subsequent loss of reconstitutable protein-mediated sugar transport. These findings demonstrate that avian erythrocyte sugar transport is mediated by a GLUT1-like sugar transport protein and that sugar transport stimulation by metabolic inhibitors results from derepression of cell surface sugar transport proteins. Lysis-resealing experiments suggest that derepression is a glutathione (OSH) dependent phenomenon. This mechanism of transport regulation contrasts with insulin stimulation of sugar transport in muscle and adipose tissue which is believed to result from recruitment of intracellular sugar transporters to the plasma membrane.

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