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1.
Virologie (Montrouge) ; 12(3): 201-213, 2008 Jun 01.
Article in French | MEDLINE | ID: mdl-36131457

ABSTRACT

The production of Human Immunodeficiency Virus-1 (HIV-1), the causative agent of AIDS, requires many interactions between viral and host cell proteins at each step of the viral cycle. The late steps of the replicative cycle of HIV-1 permit the formation of new infectious virions. These steps consist of assembly and budding of the particle, as well as the envelope glycoproteins incorporation step. Several research teams have tried to elucidate the molecular mechanism controlling the envelope glycoproteins (Env) incorporation. Recently, the first cellular cofactor required for this step, Tail-Interacting Protein of 47 kDa (TIP47), has been identified. TIP47 is required for the generation of an infectious viral particle and for the incorporation of the envelope glycoproteins into virions. In this review, we emphasize the key roles of the two major viral structural proteins, Gag and Env, in the last steps of the replicative cycle of HIV-1. We describe the biology of TIP47 and its role as a bridge between Gag and Env, during Env incorporation into new viral particles. Studies discussed in the review illustrate the key roles of proteins implicated in the intracellular trafficking pathways during the formation of the virus.

2.
Mol Cell Biol ; 21(6): 2192-202, 2001 Mar.
Article in English | MEDLINE | ID: mdl-11238952

ABSTRACT

The ubiquitin-proteasome pathway regulates gene expression through protein degradation. Here we show that the F-box protein betaTrCP, the receptor component of the SCF E3 ubiquitin ligase responsible for IkappaBalpha and beta-catenin degradation, is colocalized in the nucleus with ATF4, a member of the ATF-CREB bZIP family of transcription factors, and controls its stability. Association between the two proteins depends on ATF4 phosphorylation and on ATF4 serine residue 219 present in the context of DSGXXXS, which is similar but not identical to the motif found in other substrates of betaTrCP. ATF4 ubiquitination in HeLa cells is enhanced in the presence of betaTrCP. The F-box-deleted betaTrCP protein behaves as a negative transdominant mutant that inhibits ATF4 ubiquitination and degradation and, subsequently, enhances its activity in cyclic AMP-mediated transcription. ATF4 represents a novel substrate for the SCF(betaTrCP) complex, which is the first mammalian E3 ubiquitin ligase identified so far for the control of the degradation of a bZIP transcription factor.


Subject(s)
Cell Nucleus/metabolism , Peptide Synthases/metabolism , Transcription Factors/metabolism , Activating Transcription Factor 4 , Amino Acid Motifs , Cells, Cultured , Cyclic AMP/metabolism , GTP-Binding Proteins/genetics , GTP-Binding Proteins/metabolism , Humans , Mutation , Phosphorylation , Precipitin Tests , SKP Cullin F-Box Protein Ligases , Serine , Transcription Factors/genetics , Transcription, Genetic , beta-Transducin Repeat-Containing Proteins
3.
J Virol ; 75(6): 2982-92, 2001 Mar.
Article in English | MEDLINE | ID: mdl-11222723

ABSTRACT

Short amino acid sequences in the cytosolic domains of transmembrane proteins are recognized by specialized adaptor [corrected] proteins which are part of coated vesicles utilized to transport membrane proteins between the trans-Golgi network (TGN) and the plasma membrane (forward and backward). Previously, we and others reported that the membrane-proximal tyrosine residues Y712 (human immunodeficiency virus [HIV]) and Y721 (simian immunodeficiency virus [SIV]) in the envelope glycoprotein (Env) of the primate lentiviruses are crucial for the association of Env with clathrin-associated adaptor [corrected] complex AP-2. The same tyrosine-based endocytosis motifs in the cytosolic domains (EnvCD) of transmembrane gp41 of HIV type 1 (HIV-1) and SIV, respectively, were also shown to modulate the interaction with TGN- and endosome-based clathrin-associated complex AP-1. Our findings suggested that EnvCD binding to AP-1, unlike the association of EnvCD with AP-2, is dependent largely on residues other than Y712 and Y721. Here, we tested if motifs downstream of Y712 affect HIV-1 EnvCD-AP-1 binding and Env trafficking. Mutational analysis revealed that the C-terminal leucine-based motif in Env was crucial for the recruitment of AP-1 in vitro and in Env-expressing cells. In addition to affecting Env-AP-1 association, mutations at the C terminus of Env also altered the subcellular localization of Env, suggesting that proper post-Golgi routing of Env depends on its recruitment of AP-1. Finally, the C-terminal dileucine was shown to assist the membrane-proximal Y712 motif in restricting the cell surface expression of Env.


Subject(s)
Gene Products, env/chemistry , Gene Products, env/metabolism , HIV-1/metabolism , Membrane Proteins/metabolism , Adaptor Protein Complex delta Subunits , Amino Acid Motifs , Amino Acid Sequence , Gene Expression Regulation, Viral , Gene Products, env/genetics , Genes, env , HIV-1/chemistry , HeLa Cells , Humans , Leucine/chemistry , Leucine/genetics , Membrane Proteins/genetics , Molecular Sequence Data , Mutation , Signal Transduction , Subcellular Fractions/metabolism , Transfection
4.
Traffic ; 1(11): 871-83, 2000 Nov.
Article in English | MEDLINE | ID: mdl-11208076

ABSTRACT

The Nef protein from the human immunodeficiency virus (HIV) induces down-regulation of the CD4 and major histocompatibility complex class I molecules from the cell surface by interfering with the endocytic machinery. This work focuses on the interaction of HIV-1 Nef with the mu 1 chain of adaptor protein type 1 (AP1) complex and its contribution to the Nef-induced alterations of membrane trafficking. Two independent regions surrounding a disordered loop located in the C-terminal part of Nef are involved in mu 1 binding. Each region can separately interact with mu 1, and simultaneous point mutations within both regions are needed to abolish binding. We used CD8 chimeras in which the cytoplasmic tail was replaced by Nef mutants to show that these mu 1-binding sites contain determinants required to induce CD4 down-regulation and to target the chimera to the endocytic pathway by promoting AP1 complex recruitment. Ultrastructural analysis revealed that the CD8-Nef chimera provokes morphological alterations of the endosomal compartments and co-localizes with AP1 complexes. These data indicate that the recruitment by Nef of AP1 via binding to mu 1 participates in the connection of Nef with the endocytic pathway.


Subject(s)
Endocytosis/physiology , Genes, nef , HIV-1/genetics , HIV-1/physiology , Membrane Proteins/metabolism , Adaptor Protein Complex 1 , Adaptor Protein Complex alpha Subunits , Adaptor Proteins, Vesicular Transport , Amino Acid Sequence , Binding Sites/genetics , CD4 Antigens/metabolism , CD8 Antigens/genetics , CD8 Antigens/metabolism , Cell Compartmentation , Cell Nucleus/metabolism , Down-Regulation , Endosomes/metabolism , HeLa Cells , Humans , Microscopy, Immunoelectron , Molecular Sequence Data , Point Mutation , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Transfection
5.
J Virol ; 73(2): 1350-61, 1999 Feb.
Article in English | MEDLINE | ID: mdl-9882340

ABSTRACT

The cytoplasmic domains of the transmembrane (TM) envelope proteins (TM-CDs) of most retroviruses have a Tyr-based motif, YXXO, in their membrane-proximal regions. This signal is involved in the trafficking and endocytosis of membrane receptors via clathrin-associated AP-1 and AP-2 adaptor complexes. We have used CD8-TM-CD chimeras to investigate the role of the Tyr-based motif of human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus (SIV), and human T-leukemia virus type 1 (HTLV-1) TM-CDs in the cell surface expression of the envelope glycoprotein. Flow cytometry and confocal microscopy studies showed that this motif is a major determinant of the cell surface expression of the CD8-HTLV chimera. The YXXO motif also plays a key role in subcellular distribution of the envelope of lentiviruses HIV-1 and SIV. However, these viruses, which encode TM proteins with a long cytoplasmic domain, have additional determinants distal to the YXXO motif that participate in regulating cell surface expression. We have also used the yeast two-hybrid system and in vitro binding assays to demonstrate that all three retroviral YXXO motifs interact with the micro1 and micro2 subunits of AP complexes and that the C-terminal regions of HIV-1 and SIV TM proteins interact with the beta2 adaptin subunit. The TM-CDs of HTLV-1, HIV-1, and SIV also interact with the whole AP complexes. These results clearly demonstrate that the cell surface expression of retroviral envelope glycoproteins is governed by interactions with adaptor complexes. The YXXO-based signal is the major determinant of this interaction for the HTLV-1 TM, which contains a short cytoplasmic domain, whereas the lentiviruses HIV-1 and SIV have additional determinants distal to this signal that are also involved.


Subject(s)
Clathrin/metabolism , Gene Products, env/metabolism , HIV Envelope Protein gp41/metabolism , HIV-1/metabolism , Human T-lymphotropic virus 1/metabolism , Membrane Proteins/metabolism , Retroviridae Proteins, Oncogenic/metabolism , Simian Immunodeficiency Virus/metabolism , Viral Fusion Proteins/metabolism , Adaptor Protein Complex alpha Subunits , Adaptor Protein Complex beta Subunits , Adaptor Proteins, Vesicular Transport , Amino Acid Sequence , Amino Acid Substitution , Animals , Binding Sites , CD8 Antigens/metabolism , Cell Membrane/metabolism , Cytoplasm/metabolism , Gene Products, env/genetics , HIV Envelope Protein gp41/genetics , HIV-1/genetics , Haplorhini , HeLa Cells , Human T-lymphotropic virus 1/genetics , Humans , Intracellular Fluid , Molecular Sequence Data , Retroviridae Proteins, Oncogenic/genetics , Simian Immunodeficiency Virus/genetics , Subcellular Fractions , Tyrosine , Viral Fusion Proteins/genetics , env Gene Products, Human Immunodeficiency Virus
6.
J Virol ; 73(1): 592-600, 1999 Jan.
Article in English | MEDLINE | ID: mdl-9847364

ABSTRACT

Vpr and Vpx proteins from human and simian immunodeficiency viruses (HIV and SIV) are incorporated into virions in quantities equivalent to those of the viral Gag proteins. We demonstrate here that Vpr and Vpx proteins from distinct lineages of primate lentiviruses were able to bind to their respective Gag precursors. The capacity of HIV type 1 (HIV-1) Vpr mutants to bind to Pr55(Gag) was correlated with their incorporation into virions. Molecular analysis of these interactions revealed that they required the C-terminal p6 domain of the Gag precursors. While the signal for HIV-1 Vpr binding lies in the leucine triplet repeat region of the p6 domain reported to be essential for incorporation, SIVsm Gag lacking the equivalent region still bound to SIVsm Vpr and Vpx, indicating that the determinants for Gag binding are located upstream of this region of the p6 domain. Binding to Gag cleavage products showed that HIV-1 Vpr interacted directly with the nucleocapsid protein (NC), whereas SIVsm Vpr and Vpx did not interact with NC but with the p6 protein. These results (i) reveal differences between HIV-1 and SIVsm for the p6 determinants required for Vpr and Vpx binding to Gag and (ii) suggest that HIV-1 Vpr and SIVsm Vpr and Vpx interact with distinct cleavage products of the precursor following proteolytic processing in the virions.


Subject(s)
Gene Products, gag/metabolism , Gene Products, vpr/metabolism , HIV/metabolism , Protein Precursors/metabolism , Simian Immunodeficiency Virus/metabolism , Viral Regulatory and Accessory Proteins/metabolism , Virion/metabolism , Amino Acid Sequence , Humans , Molecular Sequence Data , Repetitive Sequences, Amino Acid , vpr Gene Products, Human Immunodeficiency Virus
7.
Immunity ; 8(4): 483-95, 1998 Apr.
Article in English | MEDLINE | ID: mdl-9586638

ABSTRACT

The surface expression of MHC I is reduced in HIV-infected cells. We show that the Nef protein affects the intracellular sorting of HLA-A and -B molecules. In the presence of Nef, these proteins accumulate in the Golgi and colocalize with clathrin-coated vesicles. MHC I modulation relies on a tyrosine-based sorting signal located in the cytoplasmic domain of HLA-A and -B heavy chains. This cryptic sorting signal becomes operative only in the presence of Nef. Nef interacts with the medium (mu) subunit of AP adaptor complexes involved in the recognition of tyrosine-based sorting signals, likely facilitating the connection between MHC I and the clathrin-dependent sorting machinery.


Subject(s)
Clathrin/metabolism , Gene Products, nef/metabolism , HLA-A Antigens/metabolism , HLA-B Antigens/metabolism , Adaptor Protein Complex alpha Subunits , Adaptor Proteins, Vesicular Transport , Amino Acid Sequence , Binding Sites , CD4 Antigens/metabolism , Clathrin/chemistry , Down-Regulation , HIV Infections/metabolism , HIV-1/metabolism , HIV-2/metabolism , HLA-A Antigens/chemistry , HLA-A Antigens/genetics , HLA-B Antigens/chemistry , HLA-B Antigens/genetics , HLA-C Antigens/chemistry , HLA-C Antigens/genetics , HLA-C Antigens/metabolism , HeLa Cells , Humans , Membrane Proteins/chemistry , Membrane Proteins/metabolism , Models, Biological , Molecular Sequence Data , Protein Conformation , Signal Transduction , Simian Immunodeficiency Virus/metabolism , nef Gene Products, Human Immunodeficiency Virus
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