Vpr cytopathicity independent of G2/M cell cycle arrest in human immunodeficiency virus type 1-infected CD4+ T cells.
The mechanism of CD4(+) T-cell depletion in human immunodeficiency virus type 1 (HIV-1)-infected individuals remains unknown, although mounting evidence suggests that direct viral cytopathicity contributes to this loss. The HIV-1 Vpr accessory protein causes cell death and arrests cells in the G(2)/M phase; however, the molecular mechanism underlying these properties is not clear. Mutation of hydrophobic residues on the surface of its third alpha-helix disrupted Vpr toxicity, G(2)/M arrest induction, nuclear localization, and self-association, implicating this region in multiple Vpr functions. Cytopathicity by virion-delivered mutant Vpr protein correlated with G(2)/M arrest induction but not nuclear localization or self-association. However, infection with whole virus encoding these Vpr mutants did not abrogate HIV-1-induced cell killing. Rather, mutant Vpr proteins that are impaired for G(2)/M block still prevented infected cell proliferation, and this property correlated with the death of infected cells. Chemical agents that inhibit infected cells from entering G(2)/M also did not reduce HIV-1 cytopathicity. Combined, these data implicate Vpr in HIV-1 killing through a mechanism involving inhibiting cell division but not necessarily in G(2)/M. Thus, the hydrophobic region of the third alpha-helix of Vpr is crucial for mediating G(2)/M arrest, nuclear localization, and self-association but dispensable for HIV-1 cytopathicity due to residual cell proliferation blockade mediated by a separate region of the protein.
Bolton
Diane L
DL
Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bldg. 10, Rm. 11N311, 10 Center Dr., Bethesda, MD 20892-1892, USA.
Lenardo
Michael J
MJ
D019943:Amino Acid Substitution / Q000235:genetics; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000821:virology*; D002453:Cell Cycle; D016923:Cell Death; D045744:Cell Line, Tumor; D003588:Cytopathogenic Effect, Viral; D016336:Gene Products, vpr / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D019169:Jurkat Cells; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D011485:Protein Binding / Q000235:genetics; D017433:Protein Structure, Secondary; D021381:Protein Transport / Q000235:genetics; D054325:vpr Gene Products, Human Immunodeficiency Virus
D016336:Gene Products, vpr; D054325:vpr Gene Products, Human Immunodeficiency Virus