HIV induces lymphocyte apoptosis by a p53-initiated, mitochondrial-mediated mechanism 1
- DAVIDE GENINI*,†,2,
- DENNIS SHEETER*,2,
- STEFFNEY ROUGHT*,‡,
- JOHN J. ZAUNDERS‡,
- SANTOS A. SUSIN§,
- GUIDO KROEMER§,
- DOUGLAS D. RICHMAN*,‡,
- DENNIS A. CARSON*,†,
- JACQUES CORBEIL*,‡,2 and
- LORENZO M. LEONI*,†,2,3
- *Departments of Medicine and
- †The Sam and Rose Stein Institute for Research on Aging, University of California San Diego, La Jolla, California 92093-0663, USA;
- ‡San Diego Health Care System and Veterans Medical Research Foundation, San Diego, California 92161, USA; and
- §Centre National de la Recherche Scientifique, UMR1599, Institut Gustave Roussy, F-94805 Villejuif, France
- ↵Correspondence: 3Correspondence: Department of Medicine-0663, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0663, USA. E-mail: lleoni{at}ucsd.edu
SPECIFIC AIMS
HIV-1 induces apoptosis and leads to CD4+ T lymphocyte depletion in humans. It is still unclear whether HIV-1 kills infected cells directly or indirectly. In this study we provide a mechanistic view on how HIV-1 induces apoptotic death of infected primary human CD4+ T lymphocytes.
PRINCIPAL FINDINGS
1. HIV damages mitochondria, leading to cytochrome c release and caspase activation
The time course of activation of the extrinsic and intrinsic pathways of apoptosis was examined after HIV-1 infection of primary CD4+ T lymphocytes. The percentage of cells undergoing apoptosis was quantified by flow cytometry and measuring the proportion of cells with sub-G1 DNA content and correlating it with HIV p24 production. Caspase activities were measured at multiple time points after infection by using specific fluorometric substrates (Fig. 1⇓ ). The pattern of caspase activation strongly suggested that the intrinsic pathway of apoptosis induction was operational. This suggestion was borne out by the following observations. The catalytic activity of the apical caspase-2 and -9 increased after 2 days, concomitantly with the activation of the executioner caspase-3. Activated caspase-6 was detectable only 72 h after infection. No activity of the death receptor-associated apical caspase-8 was observed during the infection (up to 72 h). Caspase enzymatic activities were corroborated by immunoblotting. Cleavage of the proform of caspase-3 was …
