Vpu: A Multifunctional Protein that Enhances the Pathogenesis of Human Immunodeficiency Virus Type 1

The envelope (Env) protein of human immunodeficiency virus type 2 (HIV-2) and the HIV-1 Vpu protein stimulate the release of retroviral particles from human cells that restrict virus production, an activity that we call the enhancement of virus release (EVR). We have previously shown that two separate domains in the HIV-2 envelope protein are required for this activity: a glycine-tyrosine-x-x-hydrophobic (GYxx) motif in the cytoplasmic tail and an unmapped region in the ectodomain of the protein. We here report that the cellular partner of the GYxx motif is the adaptor protein complex AP-2. The mutation of this motif or the depletion of AP-2 by RNA interference abrogated EVR activity and changed the cellular distribution of the Env from a predominantly punctate pattern to a more diffuse distribution. Since the L domain of equine infectious anemia virus (EIAV) contains a Yxx motif that interacts with AP-2, we used both wild-type and L domain-defective particles of HIV-1 and EIAV to examine whether the HIV-2 Env EVR function was analogous to L domain activity. We observed that the production of all particles was stimulated by HIV-2 Env or Vpu, suggesting that the L domain and EVR activities play independent roles in the release of retroviruses. Interestingly, we found that the cytoplasmic tail of the murine leukemia virus (MLV) Env could functionally substitute for the HIV-2 Env tail, but it did so in a manner that did not require a Yxx motif or AP-2. The cellular distribution of the chimeric HIV-2/MLV Env was significantly less punctate than the wild-type Env, although confocal analysis revealed an overlap in the steady-state locations of the two proteins. Taken together, these data suggest that the essential GYxx motif in the HIV-2 Env tail recruits AP-2 in order to direct Env to a cellular pathway or location that is necessary for its ability to enhance virus release but that an alternate mechanism provided by the MLV Env tail can functionally substitute.

Section: Discussionmentioning

confidence: 99%

Recruitment of the Adaptor Protein 2 Complex by the Human Immunodeficiency Virus Type 2 Envelope Protein Is Necessary for High Levels of Virus Release

Noble

Abada²,

Nunez-Iglesias

et al. 2006

“…Specific interaction of Vpu TM with hu-tetherin. HIV-1 Vpu protein consists of two major elements: an N-terminal TM domain that anchors Vpu in the cellular membranes and a CT consisting of two putative ␣-helices separated by a conserved phosphorylation site (21). To understand which domain of Vpu interacts with hu-tetherin, we generated HEK 293 cells stably expressing KGC-tagged hu-tetherin (KGC-hu-tetherin) (Fig.…”

Section: Fig 2 Interaction Of Tetherin and Vpu Via Tm Domains (A)mentioning

confidence: 99%

Identification of Amino Acids in the Human Tetherin Transmembrane Domain Responsible for HIV-1 Vpu Interaction and Susceptibility

Kobayashi

Ode

Yoshida

et al. 2011

105

Tetherin, also known as BST-2/CD317/HM1.24, is an antiviral cellular protein that inhibits the release of HIV-1 particles from infected cells. HIV-1 viral protein U (Vpu) is a specific antagonist of human tetherin that might contribute to the high virulence of HIV-1. In this study, we show that three amino acid residues (I34, L37, and L41) in the transmembrane (TM) domain of human tetherin are critical for the interaction with Vpu by using a live cell-based assay. We also found that the conservation of an additional amino acid at position 45 and two residues downstream of position 22, which are absent from monkey tetherins, are required for the antagonism by Vpu. Moreover, computer-assisted structural modeling and mutagenesis studies suggest that an alignment of these four amino acid residues (I34, L37, L41, and T45) on the same helical face in the TM domain is crucial for the Vpu-mediated antagonism of human tetherin. These results contribute to the molecular understanding of human tetherin-specific antagonism by HIV-1 Vpu.

“…2A). Vpu is an 81-amino-acid HIV-1 regulatory protein involved in late processing of the HIV-1 virion, prior to release of free virus from CD4 T cells, and prevents Env from binding to the CD4 T-cell receptor within the endoplasmic reticulum during processing (5,11). The Vpu peptide pool is comprised of 19 overlapping peptides.…”

Section: Cd3mentioning

confidence: 99%

Robust NK Cell-Mediated Human Immunodeficiency Virus (HIV)-Specific Antibody-Dependent Responses in HIV-Infected Subjects

Stratov

Chung

Kent

2008

108

Antibody-dependent cellular cytotoxicity (ADCC) is a potentially effective adaptive immune response to human immunodeficiency virus (HIV) infection. The study of ADCC responses has been hampered by the lack of simple methods to quantify these responses and map effective epitopes. We serendipitously observed that standard intracellular cytokine assays on fresh whole blood from a cohort of 26 HIV-infected subjects identified non-T lymphocytes expressing gamma interferon (IFN-␥) in response to overlapping linear peptides spanning HIV-1 proteins. The effector cells were CD3