Pro-apoptotic activity of HIV-1 auxiliary regulatory protein Vpr is subtype-dependent and potently enhanced by nonconservative changes of the leucine residue at position 64.
Destruction of CD4+ T cells, the hallmark of AIDS, is caused in part by HIV-1-induced apoptosis of both infected cells and noninfected "bystander" cells. The HIV-1 auxiliary regulatory protein Vpr has been shown to harbor a pro-apoptotic activity that may contribute to cellular and tissue damage during AIDS pathogenesis. The biochemical mechanism of this Vpr function remains unclear. In this report, substitutions of a single amino acid residue Leu64 with Pro, Ala, or Arg are shown to dramatically enhance the pro-apoptotic activity of Vpr, as evidenced by the degradation of cellular DNA into fragments of 200-bp increments. Substitutions of Leu64 with conservative residues have no effect. The pro-apoptotic activity of the VprL64P mutant also requires activation of caspase(s) and is inhibited by the secondary mutation I61A, indicating a high specificity for Vpr-induced apoptosis. Among the three HIV-1 subtypes examined, a subtype B Vpr and an A/G subtype recombinant Vpr have a moderate level of pro-apoptotic activity, whereas a subtype D Vpr has no detectable activity. However, the L64P mutation efficiently enhances the pro-apoptotic potential of the subtype B and subtype D Vpr molecules but not that of the A/G recombinant Vpr. It is hypothesized that Vpr molecules from different HIV-1 subtypes as well as Vpr variants that emerge during HIV-1 infection may have different pro-apoptotic potentials and contribute to the diversity of AIDS pathogenesis.
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D053938:DNA Fragmentation; D004622:Embryo, Mammalian; D004789:Enzyme Activation; D015870:Gene Expression; D016336:Gene Products, vpr / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D015497:HIV-1 / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D007668:Kidney; D007930:Leucine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014162:Transfection; D054325:vpr Gene Products, Human Immunodeficiency Virus
D016336:Gene Products, vpr; D011994:Recombinant Proteins; D054325:vpr Gene Products, Human Immunodeficiency Virus; D004247:DNA; D020169:Caspases; D007930:Leucine