GPG-NH2acts via the metabolite αHGA to target HIV-1 Env to the ER-associated protein degradation pathway

Alenka Jejcic,Anders Vahlne,Stefan Höglund

doi:10.1186/1742-4690-7-20

Alenka Jejcic, Anders Vahlne + Show 1 more

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https://doi.org/10.1186/1742-4690-7-20

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Journal: Retrovirology	Publication Date: Mar 15, 2010
Citations: 22	License type: cc-by

Affiliation: Karolinska Institutet, Uppsala University

Abstract

BackgroundThe synthetic peptide glycyl-prolyl-glycine amide (GPG-NH2) was previously shown to abolish the ability of HIV-1 particles to fuse with the target cells, by reducing the content of the viral envelope glycoprotein (Env) in progeny HIV-1 particles. The loss of Env was found to result from GPG-NH2 targeting the Env precursor protein gp160 to the ER-associated protein degradation (ERAD) pathway during its maturation. However, the anti-viral effect of GPG-NH2 has been shown to be mediated by its metabolite α-hydroxy-glycineamide (αHGA), which is produced in the presence of fetal bovine serum, but not human serum. In accordance, we wanted to investigate whether the targeting of gp160 to the ERAD pathway by GPG-NH2 was attributed to its metabolite αHGA.ResultsIn the presence of fetal bovine serum, GPG-NH2, its intermediary metabolite glycine amide (G-NH2), and final metabolite αHGA all induced the degradation of gp160 through the ERAD pathway. However, when fetal bovine serum was replaced with human serum only αHGA showed an effect on gp160, and this activity was further shown to be completely independent of serum. This indicated that GPG-NH2 acts as a pro-drug, which was supported by the observation that it had to be added earlier to the cell cultures than αHGA to induce the degradation of gp160. Furthermore, the substantial reduction of Env incorporation into HIV-1 particles that occurs during GPG-NH2 treatment was also achieved by treating HIV-1 infected cells with αHGA.ConclusionsThe previously observed specificity of GPG-NH2 towards gp160 in HIV-1 infected cells, resulting in the production of Env (gp120/gp41) deficient fusion incompetent HIV-1 particles, was most probably due to the action of the GPG-NH2 metabolite αHGA.

Highlights

The synthetic peptide glycyl-prolyl-glycine amide (GPG-NH2) was previously shown to abolish the ability of HIV-1 particles to fuse with the target cells, by reducing the content of the viral envelope glycoprotein (Env) in progeny HIV-1 particles
The HIV-1 infection is initiated by its Env, where gp120 directs binding to the target cell, and gp41 mediates the fusion of the viral membrane with the host cell plasma membrane, which results in the delivery of the viral content into the cell [4]
To evaluate whether the targeting of gp160 to the endoplasmic reticulum (ER)-associated protein degradation (ERAD) pathway is due to the action of GPG-NH2, its intermediate metabolite G-NH2, or its final metabolite aHGA the respective drugs were added to HeLa-tat III cells at indicated concentrations 2 h after transfection with the gp160 expressing plasmid pNL1.5EU

Summary

Introduction

The synthetic peptide glycyl-prolyl-glycine amide (GPG-NH2) was previously shown to abolish the ability of HIV-1 particles to fuse with the target cells, by reducing the content of the viral envelope glycoprotein (Env) in progeny HIV-1 particles. Prevention of viral spreading by targeting viral entry can be achieved by inhibiting the function of gp120/gp41 [5,6] It might be accomplished late in the viral replication cycle by negatively affecting the maturation of gp160. Treatment of HIV-1 infected cells with the synthetic peptide glycyl-prolylglycine amide (GPG-NH2) targets gp160 to the ER-associated protein degradation (ERAD) pathway. To be initiated, this process requires the ER quality control machinery to recognize gp160 as terminally misfolded and results in its retro-translocation to the cytoplasm. HIV1 particles produced in the presence of GPG-NH2 have a significantly reduced content of gp120/gp on their surface [10]

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