title: Effects of chronic alcohol drinking on receptor-binding, internalization, and degradation of human immunodeficiency virus 1 envelope protein gp120 in hepatocytes.
abstract: Although alcohol drinking increases susceptibility to human immunodeficiency virus (HIV) infection, possible mechanisms underlying the effects of alcohol are not yet known. Since the HIV envelope protein gp120 plays a key role in progression of HIV infection, the aim of the present study was to evaluate the toxicity and degradation of gp120 in hepatocytes isolated from liver of alcohol-preferring rats drinking either 15% ethanol in water or pure water for 70 days. The hypothesis was that alcohol drinking augmented the toxicity, but suppressed degradation of gp120. Hepatocytes from water-drinking rats (C-cells) or ethanol-drinking rats (Et-cells) were treated with laptacystin, anti-CD4 antibodies, CCR5 antagonist, or mannose, followed by [(125)I]gp120 or native gp120. At predetermined intervals, control (C) and ethanol exposed (Et) cells were analyzed for toxicity and degradation of gp120. In C-cells, [(125)I]gp120 binding and internalization peaked within 5-45 min and remained elevated for up to 10h and then decreased gradually. In Et-cells, [(125)I]gp120 binding peaked comparably to C-cells, but the binding remained to the peak level throughout the experimental period. C-cells exhibited the lysosomal/ubiquitin-mediated degradation of intracellular gp120, resulting in released gp120 fragments into the incubation medium that suppressed gp120-CD4 binding, improved cell viability, and inhibited gp120-induced apoptosis. Ethanol drinking suppressed gp120 degradation in and release of gp120 fragments from hepatocytes. The incubation medium of Et-cells did not suppress gp120-CD4 binding or the gp120-mediated apoptosis in hepatocytes. Thus, chronic alcohol drinking augmented the adverse effects of gp120 possibly by suppressing its degradation in hepatocytes. The present observation also suggests that a number of CCR5 or ubiquitin-based therapeutic drugs may not be effective in suppressing HIV infection in alcohol-drinking subjects.
authors.affiliation: Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, 1333 Gortner Avenue, St Paul, Minnesota 55108, USA. singh001@umn.edu
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Singh
authors.forename: Yin
authors.initials: Y
authors.lastname: Jiang
authors.forename: Shveta
authors.initials: S
authors.lastname: Gupta
mesh_terms: D000428:Alcohol Drinking / Q000378:metabolism*; D000437:Alcoholism / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D017209:Apoptosis / Q000187:drug effects; D015704:CD4 Antigens / Q000276:immunology / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D055316:Cystatin C; D015891:Cystatins / Q000378:metabolism; D004705:Endocytosis; D000431:Ethanol / Q000494:pharmacology*; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006868:Hydrolysis; D008297:Male; D008358:Mannose / Q000494:pharmacology; D008969:Molecular Sequence Data; D011485:Protein Binding; D051381:Rats; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D019713:Receptors, CCR5 / Q000378:metabolism; D020539:Sequence Analysis, Protein; D013997:Time Factors; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D000906:Antibodies; D015704:CD4 Antigens; C525030:CST3 protein, human; D002492:Central Nervous System Depressants; C525032:Cst3 protein, rat; D055316:Cystatin C; D015891:Cystatins; D015699:HIV Envelope Protein gp120; C484953:MPR300 protein, rat; D017527:Receptor, IGF Type 2; D019713:Receptors, CCR5; D025801:Ubiquitin; C514793:gp120 protein, Human immunodeficiency virus 1; D000431:Ethanol; D008358:Mannose