HIV-1 Vpr displays natural protein-transducing properties: implications for viral pathogenesis.
The 14-kDa Vpr protein of human immunodeficiency virus type 1 (HIV-1) serves multiple functions in the retroviral life cycle, including the enhancement of viral replication in nondividing macrophages, the induction of G2 cell-cycle arrest in proliferating T lymphocytes, and the modulation of HIV-1-induced apoptosis. Extracellular Vpr has been detected in the sera and cerebral spinal fluid of HIV-infected patients. However, it is not known whether such forms of Vpr are biologically active. Vpr contains a carboxy-terminal basic amino acid rich segment stretch that is homologous to domains that mediate the energy- and receptor-independent cellular uptake of polypeptides by a process termed protein transduction. Similar functional protein-transducing domains are present in HIV-1 Tat, herpes simplex virus-1 DNA-binding protein VP22, and the Drosophila antennapedia homeotic transcription factor. We now demonstrate effective transduction of biologically active, synthetic Vpr (sVpr) as well as the Vpr-beta-galactosidase fusion protein. However, in contrast to other transducing proteins, Vpr transduction is not enhanced by protein denaturation, and Vpr's carboxy-terminal basic domain alone is not sufficient for its transduction across biological membranes. In contrast, the full-length Vpr protein effectively transduces a broad array of cells, leading to dose-dependent G2 cell-cycle arrest and apoptosis. Addition of Vpr into the extracellular medium also rescues the replication of Vpr-deficient strains of HIV-1 in human macrophage cultures. Native Vpr may thus be optimized for protein transduction, a feature that might enhance and extend the pathological effects of HIV infection.
Sherman
Michael P
MP
Gladstone Institute of Virology and Immunology, San Fransisco, California 94141, USA.
Schubert
Ulrich
U
Williams
Samuel A
SA
de Noronha
Carlos M C
CM
Kreisberg
Jason F
JF
Henklein
Peter
P
Greene
Warner C
WC
D002461:Cell Line, Transformed; D016336:Gene Products, vpr / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D054325:vpr Gene Products, Human Immunodeficiency Virus
D016336:Gene Products, vpr; D054325:vpr Gene Products, Human Immunodeficiency Virus