The role of N‐glycosylation in the targeting and stability of GLUT1 glucose transporter

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Abstract
The cDNAs encoding the GLUT1 glucose transporter protein were altered by site‐directed mutagenesis at consensus sites for the addition of N‐linked glycosylation. These cDNAs were transfected into CHO cells with an expression vector and the subcellular distribution and stability of the expressed glycosylation‐defective GLUT1 protein were analyzed. Immunohistochemical analysis with a specific antibody demonstrated that a significant portion of glycosylation‐defective GLUT1 protein remained in the intracellular compartment. By contrast, most of the wild‐type GLUT1 proteins expressed with the same procedures resided in the plasma membranes. Metabolic labeling studies revealed that the half‐life of the glycosylation‐defective GLUT1 protein was significantly shorter than that of wild‐type GLUT1 protein. These results indicate that N‐glycosylation of the glucose transporter affects its intracellular targeting and protein stability.