Glucose is a basic energy source for most mammalian cells. With the notable exception of luminal epithelial cells in the intestine and kidney, glucose transport occurs by facilitated diffusion. Molecular cloning studies have revealed a family of facilitated glucose transporters, or “GLUTs”, the members of which have a high degree of amino acid and structural homology (Fig. 1). Differences in transport kinetics, substrate specificity, tissue expression and subcellular targeting presumably contribute to the metabolic phenotype of a particular cell (Table 1). In this article we will focus on the unique subcellular targeting properties of facilitated glucose transporters because these reveal some of the critical physiological functions of these proteins.
Facilitated glucose transporters provide an ideal system for studying the molecular regulation of membrane protein targeting. In view of the structural similarity between the different isoforms (Fig. 1) it is possible to construct chimeric proteins...
