Isoform-Selective Targeting of Facilitative Glucose Transporters with Small Molecule Inhibitors

Abstract

There are currently 14 known mammalian facilitative glucose transporters (GLUTs) that serve a variety of critical roles in maintaining glucose homeostasis. The ability to potently target glucose transport in an isoform-selective manner is of paramount importance to investigate the normal function of these transporter isoforms and their individual contributions to disease pathogenesis. A number of GLUT isoform-selective small molecule inhibitors have been identified. To investigate the structural basis of GLUT inhibition and facilitate further refinement of the efficacy and selectivity of these antagonists, we performed kinetic analysis of the effects of WBZ-117, C-20, BAY-876 and several HIV protease inhibitors, on 3H-2-deoxyglucose uptake into cell lines selectively over-expressing GLUT1, GLUT4 or a T30I H160N GLUT1 mutant transporter. Several important findings were made: 1) based on Ki(app) measurements, indinavir, lopinavir, WZB-117 and C-20 selectively inhibit GLUT4 13-55 fold vs. GLUT1. Although structurally divergent, the potency of these 4 compounds against GLUT1 can be markedly enhanced to levels approximating those for GLUT4 by substituting just two GLUT1 amino acids located in the glucose permeation pathway to those found in GLUT4 (T30I and H160N); 2) nelfinavir is a weak GLUT4 inhibitor but acts as a GLUT1 activator, increasing transport activity 1.4-fold; 3) saquinavir selectively inhibits GLUT4 and the T30I H160N GLUT1 mutant, and exhibits complex kinetic patterns in the mutant cell line consistent with a two site model for partial inhibition; 4) kinetic analysis revealed that selective GLUT1 inhibitor, BAY-876, is a noncompetitive inhibitor of this transporter. Taken together, these data provide key structural insights into the ability of small molecules to alter GLUT function that will aid in the development of novel isoform-selective drugs for glucose-dependent diseases. Disclosure M. Heitmeier: None. R.C. Hresko: None. M. Shanmugam: None. P.W. Hruz: None.