Human Immunodeficiency Virus Type 1 Vpr Interacts with Antiapoptotic Mitochondrial Protein HAX-1

ABSTRACT Human immunodeficiency virus type 1 viral protein R (Vpr) is required for viral pathogenesis and has been implicated in T-cell apoptosis through its activation of caspase 3 and caspase 9 and perturbation of mitochondrial membrane potential. To understand better Vpr-mitochondria interaction, we report here the identification of antiapoptotic mitochondrial protein HAX-1 as a novel Vpr target. We show that Vpr and HAX-1 physically associate with each other. Overexpression of Vpr in cells dislocates HAX-1 from its normal residence in mitochondria and creates mitochondrion instability and cell death. Conversely, overexpression of HAX-1 suppressed the proapoptotic activity of Vpr.

Download Full-text

Fusion-Induced Apoptosis Contributes to Thymocyte Depletion by a Pathogenic Human Immunodeficiency Virus Type 1 Envelope in the Human Thymus

Journal of Virology ◽

10.1128/jvi.01382-06 ◽

2006 ◽

Vol 80 (22) ◽

pp. 11019-11030 ◽

Cited By ~ 21

Author(s):

Eric G. Meissner ◽

Liguo Zhang ◽

S. Jiang ◽

Lishan Su

Keyword(s):

Human Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Caspase 3 ◽

Fusion Inhibitors ◽

Immunodeficiency Virus ◽

Induced Apoptosis ◽

Hiv 1 ◽

Active Caspase

ABSTRACT The mechanisms of CD4+ T-cell depletion during human immunodeficiency virus type 1 (HIV-1) infection remain incompletely characterized. Of particular importance is how CD4+ T cells are depleted within the lymphoid organs, including the lymph nodes and thymus. Herein we characterize the pathogenic mechanisms of an envelope from a rapid progressor (R3A Env) in the NL4-3 backbone (NL4-R3A) which is able to efficiently replicate and deplete CD4+ thymocytes in the human fetal-thymus organ culture (HF-TOC). We demonstrate that uninterrupted replication is required for continual thymocyte depletion. During depletion, NL4-R3A induces an increase in thymocytes which uptake 7AAD, a marker of cell death, and which express active caspase-3, a marker of apoptosis. While 7AAD uptake is observed predominantly in uninfected thymocytes (p24−), active caspase-3 is expressed in both infected (p24+) and uninfected thymocytes (p24−). When added to HF-TOC with ongoing infection, the protease inhibitor saquinavir efficiently suppresses NL4-R3A replication. In contrast, the fusion inhibitors T20 and C34 allow for sustained HIV-1 production. Interestingly, T20 and C34 effectively prevent thymocyte depletion in spite of this sustained replication. Apoptosis of both p24− and p24+ thymocytes appears to be envelope fusion dependent, as T20, but not saquinavir, is capable of reducing thymocyte apoptosis. Together, our data support a model whereby pathogenic envelope-dependent fusion contributes to thymocyte depletion in HIV-1-infected thymus, correlated with induction of apoptosis in both p24+ and p24− thymocytes.

Download Full-text

A Carboxy-Terminally Truncated Form of the Human Immunodeficiency Virus Type 1 Vpr Protein Induces Apoptosis via G1 Cell Cycle Arrest

Journal of Virology ◽

10.1128/jvi.74.13.6058-6067.2000 ◽

2000 ◽

Vol 74 (13) ◽

pp. 6058-6067 ◽

Cited By ~ 30

Author(s):

Masako Nishizawa ◽

Masakazu Kamata ◽

Ryoichi Katsumata ◽

Yoko Aida

Keyword(s):

Cell Cycle ◽

Human Immunodeficiency Virus ◽

Cell Proliferation ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Caspase 3 ◽

Annexin V ◽

Truncated Form ◽

Immunodeficiency Virus

ABSTRACT Viral protein R (Vpr) of human immunodeficiency virus type 1 inhibits cell proliferation by arresting the cell cycle at the G2 phase and inducing to apoptosis after G2arrest. We have reported previously that C81, a carboxy-terminally truncated form of Vpr, interferes with cell proliferation via a novel pathway that is distinct from G2 arrest. However, the mechanism of this effect of C81 is unknown. We demonstrate here that C81 can induce apoptosis via G1 arrest of the cell cycle. Immunostaining for various markers of stages of the cell cycle and flow cytometry analysis of DNA content showed that most HeLa cells that had been transiently transfected with a C81 expression vector were arrested at the G1 phase and not at the G2 or S phase of the cell cycle. Staining for annexin V, which binds phosphatidylserine on the plasma membrane, as an early indicator of apoptosis and measurement of the activity of caspase-3, a signaling molecule in apoptotic pathways, indicated that C81 is a strong inducer of apoptosis. Expression of C81 induced the condensation, fragmentation, and clumping of chromatin that are typical of apoptosis. Furthermore, the kinetics of the C81-induced G1 arrest were closely correlated with changes in the number of annexin V-positive cells and the activity of caspase-3. Replacement of Ile or Leu residues by Pro at positions 60, 67, 74, and 81 within the leucine zipper-like domain of C81 revealed that Ile60, Leu67, and Ile74 play important roles both in the C81-induced G1 arrest and in apoptosis. Thus, it appears that C81 induces apoptosis through pathways that are identical to those utilized for G1 arrest of the cell cycle. It has been reported that Ile60, Leu67, and Ile74 also play an important role in the C81-induced suppression of growth. These results suggest that the suppression of growth induced by C81 result in apoptosis that is independent of G2 arrest of the cell cycle.

Download Full-text