6th International Workshop on Adverse Drug Reactions and Lipodystrophy in HIV 25–28 October 2004 - Washington, DC, USA

A STRUCTURAL BASIS FOR THE EFFECTS OF HIV PROTEASE INHIBITORS ON GLUT4 ACTIVITY

Antiviral Therapy 2004; 9(6):L5 (abstract no. 5)

P Hruz, J Hertel, H Struthers and C Baird Horj
Washington University, St Louis, Mo., USA

HIV protease inhibitors (PIs) act as potent reversible noncompetitive inhibitors of GLUT4 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 aromatic di- and tripeptides containing structural elements found in PIs were screened for their ability to inhibit 2-deoxyglucose transport in primary rat adipocytes. This analysis identified the peptide oxybenzylcarbonyl-His-Phe-Phe-O-ethyl (zHFFe) as a potent inhibitor of zero-trans glucose flux with a Ki of 25 µM, comparable with the binding affinities of PIs to GLUT4. In addition, like PIs, glucose transport inhibition by this peptide was acute, noncompetitive and readily reversible. Within a Xenopus oocyte expression system, 200 µM zHFFe acutely and reversibly inhibited GLUT4- mediated glucose uptake by 69% compared with untreated controls, whereas GLUT1 activity was unaffected at the same peptide concentration. To characterize the direct peptide–protein interactions that mediate GLUT4 inhibition, intact adipocytes were treated with a photoactivatable derivative of zHFFe, zHFF-P-benzoylphenylalanine-[¹²⁵I]-Tyr-O-ethyl. The results of this analysis showed that a protein with molecular weight identical to GLUT4 (50 kDa) was selectively labelled by the photoactivatable peptide and that 500 µM indinavir effectively protected against photolabelling. Furthermore, GLUT4 was found to selectively bind to a peptide affinity column containing the zHFF sequence. These data establish a structural basis for PI effects on GLUT4 activity and support direct binding of PIs to the transport protein as the mechanism for acute inhibition of insulin-stimulated glucose uptake. Moreover, the identification of isoform selective peptide inhibitors of GLUT4 provides novel tools for studying both normal glucose transport and the alterations in glucose homeostasis seen in patients treated with HIV protease inhibitors.

2004-10-25
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