A Structural Basis for the Acute Effects of HIV Protease Inhibitors on GLUT4 Intrinsic Activity

Johann Hertel,Heidi Struthers,Christal Baird Horj,Paul W Hruz

doi:10.1074/jbc.m410826200

Abstract

Human immunodeficiency virus (HIV) protease inhibitors (PIs) act as reversible noncompetitive inhibitors of GLUT4 with binding affinities in the low micromolar range and are known to contribute to alterations in glucose homeostasis during treatment of HIV infection. As aspartyl protease inhibitors, these compounds all possess a core peptidomimetic structure together with flanking hydrophobic moieties. To determine the molecular basis for GLUT4 inhibition, a family of related oligopeptides containing structural elements found in PIs was screened for their ability to inhibit 2-deoxyglucose transport in primary rat adipocytes. The peptide oxybenzylcarbonyl-His-Phe-Phe-O-ethyl ester (zHFFe) was identified as a potent inhibitor of zero-trans glucose flux with a K(i) of 26 mum. Similar to PIs, transport inhibition by this peptide was acute, noncompetitive, and reversible. Within a Xenopus oocyte expression system, zHFFe acutely and reversibly inhibited GLUT4-mediated glucose uptake, whereas GLUT1 activity was unaffected at concentrations as high as 1 mm. The related photoactivatable peptide zHFF-p-benzoylphenylalanine-[(125)I]Tyr-O-ethyl ester selectively labeled GLUT4 in rat adipocytes and indinavir effectively protected against photolabeling. Furthermore, GLUT4 bound to a peptide affinity column containing the zHFF sequence and was eluted by indinavir. These data establish a structural basis for PI effects on GLUT4 activity and support the direct binding of PIs to the transport protein as the mechanism for acute inhibition of insulin-stimulated glucose uptake.

Highlights

The clinical use of HIV1 protease inhibitors (PIs) has led to dramatic improvements in Human immunodeficiency virus (HIV)-related morbidity and mortality [1]
Elucidation of the specific structural features of PIs that confer their ability to inhibit GLUT4 would facilitate efforts to define the molecular mechanism for this effect but could provide a rationale for a way to design newer generations of PIs that retain their efficacy in treating HIV infection without producing insulin resistance
Aromatic Peptide Effects on GLUT4 Activity—All HIV protease inhibitors share a similar core structure that resembles the aromatic peptide backbone that acts as the native substrate for the HIV type 1 protease (Fig. 1)

Summary

Introduction

The clinical use of HIV1 protease inhibitors (PIs) has led to dramatic improvements in HIV-related morbidity and mortality [1]. These data establish a structural basis for PI effects on GLUT4 activity and support the direct binding of PIs to the transport protein as the mechanism for acute inhibition of insulin-stimulated glucose uptake.

Results

Conclusion