scholarly journals Cell-Type-Dependent Targeting of Human Immunodeficiency Virus Type 1 Assembly to the Plasma Membrane and the Multivesicular Body

2004 ◽  
Vol 78 (3) ◽  
pp. 1552-1563 ◽  
Author(s):  
Akira Ono ◽  
Eric O. Freed
Keyword(s):  
Human Immunodeficiency Virus ◽  
Plasma Membrane ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Multivesicular Body ◽  
Cell Type ◽  
Gag Proteins ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) assembly-and-release pathway begins with the targeting of the Gag precursor to the site of virus assembly. The molecular mechanism by which Gag is targeted to the appropriate subcellular location remains poorly understood. Based on the analysis of mutant Gag proteins, we and others have previously demonstrated that a highly basic patch in the matrix (MA) domain of Gag is a major determinant of Gag transport to the plasma membrane. In this study, we determined that in HeLa and T cells, the MA mutant Gag proteins that are defective in plasma membrane targeting form virus particles in a CD63-positive compartment, defined as the late endosome or multivesicular body (MVB). Interestingly, we find that in primary human macrophages, both wild-type (WT) and MA mutant Gag proteins are targeted specifically to the MVB. Despite the fact that particle assembly in macrophages occurs at an intracellular site rather than at the plasma membrane, we observe that WT Gag expressed in this cell type is released as extracellular virions with high efficiency. These results demonstrate that Gag targeting to and assembly in the MVB are physiologically important steps in HIV-1 virus particle production in macrophages and that particle release in this cell type may follow an exosomal pathway. To determine whether Gag targeting to the MVB is the result of an interaction between the late domain in p6Gag and the MVB sorting machinery (e.g., TSG101), we examined the targeting and assembly of Gag mutants lacking p6. Significantly, the MVB localization of Gag was still observed in the absence of p6, suggesting that an interaction between Gag and TSG101 is not required for Gag targeting to the MVB. These data are consistent with a model for Gag targeting that postulates two different cellular binding partners for Gag, one on the plasma membrane and the other in the MVB.

scholarly journals Productive Human Immunodeficiency Virus Type 1 Assembly Takes Place at the Plasma Membrane

2007 ◽  
Vol 81 (14) ◽  
pp. 7476-7490 ◽  
Author(s):  
Andrés Finzi ◽  
Alexandre Orthwein ◽  
Johanne Mercier ◽  
Éric A. Cohen
Keyword(s):  
Human Immunodeficiency Virus ◽  
Plasma Membrane ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Multivesicular Body ◽  
Subcellular Fractionation ◽  
Particle Assembly ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Gag proteins are necessary and sufficient to direct human immunodeficiency virus type 1 (HIV-1) particle assembly and budding. Recent evidence suggests that Gag targeting to late endosomal/multivesicular body (LE/MVB) compartments occurs prior to viral particle budding at the plasma membrane (PM). However, the route that Gag follows before reaching its steady-state destinations still remains a subject of debate. Using a subcellular fractionation method that separates PM from LE/MVB combined with pulse-chase labeling, we analyzed Gag trafficking in HIV-1-producing HEK 293T cells. Our results reveal that the majority of newly synthesized Gag is primarily targeted to the PM. While PM-targeted Gag was efficiently released, a significant fraction of the remaining cell surface-associated Gag was found to be subsequently internalized to LE/MVB, where it accumulated, thus accounting for the majority of LE/MVB-associated Gag. Importantly, this accumulation of Gag in LE/MVB was found to be cholesterol dependent since it was sensitive to the sterol-binding drugs filipin and methyl-β-cyclodextrin. These results point towards the PM as being the primary site of productive HIV-1 assembly in cells that also support Gag accumulation in intracellular compartments.

scholarly journals Human ESCRT-II Complex and Its Role in Human Immunodeficiency Virus Type 1 Release

2006 ◽  
Vol 80 (19) ◽  
pp. 9465-9480 ◽  
Author(s):  
Charles Langelier ◽  
Uta K. von Schwedler ◽  
Robert D. Fisher ◽  
Ivana De Domenico ◽  
Paul L. White ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Protein Sorting ◽  
Growth Factor Receptor ◽  
Multivesicular Body ◽  
Vesicle Formation ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The budding of many enveloped RNA viruses, including human immunodeficiency virus type 1 (HIV-1), requires some of the same cellular machinery as vesicle formation at the multivesicular body (MVB). In Saccharomyces cerevisiae, the ESCRT-II complex performs a central role in MVB protein sorting and vesicle formation, as it is recruited by the upstream ESCRT-I complex and nucleates assembly of the downstream ESCRT-III complex. Here, we report that the three subunits of human ESCRT-II, EAP20, EAP30, and EAP45, have a number of properties in common with their yeast orthologs. Specifically, EAP45 bound ubiquitin via its N-terminal GRAM-like ubiquitin-binding in EAP45 (GLUE) domain, both EAP45 and EAP30 bound the C-terminal domain of TSG101/ESCRT-I, and EAP20 bound the N-terminal half of CHMP6/ESCRT-III. Consistent with its expected role in MVB vesicle formation, (i) human ESCRT-II localized to endosomal membranes in a VPS4-dependent fashion and (ii) depletion of EAP20/ESCRT-II and CHMP6/ESCRT-III inhibited lysosomal targeting and downregulation of the epidermal growth factor receptor, albeit to a lesser extent than depletion of TSG101/ESCRT-I. Nevertheless, HIV-1 release and infectivity were not reduced by efficient small interfering RNA depletion of EAP20/ESCRT-II or CHMP6/ESCRT-III. These observations indicate that there are probably multiple pathways for protein sorting/MVB vesicle formation in human cells and that HIV-1 does not utilize an ESCRT-II-dependent pathway to leave the cell.

scholarly journals Kinesin KIF4 Regulates Intracellular Trafficking and Stability of the Human Immunodeficiency Virus Type 1 Gag Polyprotein

2008 ◽  
Vol 82 (20) ◽  
pp. 9937-9950 ◽  
Author(s):  
Nathaniel W. Martinez ◽  
Xiaoxiao Xue ◽  
Reem G. Berro ◽  
Geri Kreitzer ◽  
Marilyn D. Resh
Keyword(s):  
Human Immunodeficiency Virus ◽  
Plasma Membrane ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Particle Production ◽  
Particle Assembly ◽  
Gag Protein ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Retroviral Gag proteins are synthesized as soluble, myristoylated precursors that traffic to the plasma membrane and promote viral particle production. The intracellular transport of human immunodeficiency virus type 1 (HIV-1) Gag to the plasma membrane remains poorly understood, and cellular motor proteins responsible for Gag movement are not known. Here we show that disrupting the function of KIF4, a kinesin family member, slowed temporal progression of Gag through its trafficking intermediates and inhibited virus-like particle production. Knockdown of KIF4 also led to increased Gag degradation, resulting in reduced intracellular Gag protein levels; this phenotype was rescued by reintroduction of KIF4. When KIF4 function was blocked, Gag transiently accumulated in discrete, perinuclear, nonendocytic clusters that colocalized with endogenous KIF4, with Ubc9, an E2 SUMO-1 conjugating enzyme, and with SUMO. These studies identify a novel transit station through which Gag traffics en route to particle assembly and highlight the importance of KIF4 in regulating HIV-1 Gag trafficking and stability.

scholarly journals Analysis of Human Immunodeficiency Virus Type 1 Gag Ubiquitination

2005 ◽  
Vol 79 (14) ◽  
pp. 9134-9144 ◽  
Author(s):  
Eva Gottwein ◽  
Hans-Georg Kräusslich
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Gag Protein ◽  
Gag Proteins ◽  
Immunodeficiency Virus ◽  
Lysine Residues ◽  
The Matrix ◽  
Hiv 1

ABSTRACT Ubiquitin is important for the release of human immunodeficiency virus type 1 (HIV-1) and several other retroviruses, but the functional significance of Gag ubiquitination is unknown. To address this problem, we decided to analyze Gag ubiquitination in detail. A low percentage of the HIV-1 p6 protein has previously been shown to be ubiquitinated, and published mutagenesis data suggested that Gag ubiquitination is largely lost upon mutation of the two lysine residues in p6. In this study, we show that Gag proteins lacking the p6 domain or the two lysine residues within p6 are ubiquitinated at levels comparable to those of the wild-type Gag protein. We detected monoubiquitinated forms of the matrix (MA), capsid (CA), and nucleocapsid (NC) proteins in mature virus preparations. Protease digestion of Gag polyproteins extracted from immature virions indicated that ubiquitinated MA, CA, and possibly NC are as abundant as ubiquitinated p6. The HIV-1 late-domain motifs PTAP and LRSLF were not required for Gag ubiquitination, and mutation of the PTAP motif even resulted in an increase in the amount of Gag-Ub conjugates detected. Finally, at steady state, ubiquitinated Gag proteins were not enriched in either membrane-associated or virus-derived Gag fractions. In summary, these results indicate that HIV-1 Gag can be monoubiquitinated in all domains and that ubiquitination of lysine residues outside p6 may thus contribute to viral release and/or infectivity.

scholarly journals Deletion Mutagenesis within the Dimerization Initiation Site of Human Immunodeficiency Virus Type 1 Results in Delayed Processing of the p2 Peptide from Precursor Proteins

1999 ◽  
Vol 73 (7) ◽  
pp. 6147-6151 ◽  
Author(s):  
Chen Liang ◽  
Liwei Rong ◽  
Elana Cherry ◽  
Lawrence Kleiman ◽  
Michael Laughrea ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Point Mutations ◽  
Initiation Site ◽  
Gag Proteins ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Dimerization Initiation Site

ABSTRACT Previous work has shown that deletions of genomic segments at nucleotide (nt) positions +238 to +253, i.e., construct BH10-LD3, or nt positions +261 to +274, i.e., construct BH10-LD4, within the human immunodeficiency virus type 1 (HIV-1) dimerization initiation site (DIS) destroyed DIS secondary structure and dramatically reduced viral replication capacity. Surprisingly, two point mutations located within the viral peptide 2 (p2) and nucleocapsid (NC) protein termed MP2 and MNC, respectively, were able to compensate for this defect. Since the MP2 mutation involves an amino acid substitution near the cleavage site between p2 and NC, we investigated the effects of the above-mentioned deletions on the processing of Gag proteins. Immunoprecipitation assays performed with monoclonal antibodies against viral capsid (CA) (p24) protein showed that p2 was cleaved from CA with less efficiency in viruses that contained the LD3 and LD4 deletions than in wild-type viruses. The presence of the two compensatory mutations, MP2 and MNC, increased the efficiency of the cleavage of p2 from CA, but neither mutation alone had this effect or was sufficient to compensate for the observed impairment in infectiousness. A virus that contained both of the above-mentioned deletions within the DIS was also impaired in regard to processing and infectiousness, and it could likewise be compensated by the MP2 and MNC point mutations. These results suggest that the DIS region of HIV-1 RNA plays an important role in the processing of Gag proteins.

scholarly journals Human Immunodeficiency Virus Type 1 Gag Contains a Dileucine-Like Motif That Regulates Association with Multivesicular Bodies

2004 ◽  
Vol 78 (11) ◽  
pp. 6013-6023 ◽  
Author(s):  
O. Wolf Lindwasser ◽  
Marilyn D. Resh
Keyword(s):  
Human Immunodeficiency Virus ◽  
Plasma Membrane ◽  
Human Immunodeficiency Virus Type ◽  
Particle Production ◽  
Endocytic Pathway ◽  
Multivesicular Bodies ◽  
Gag Proteins ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Multivesicular bodies (MVBs) are cholesterol-enriched organelles formed by the endocytic pathway. The topology of vesicle formation in MVBs is identical to that of retroviral budding from the plasma membrane, and budding of human immunodeficiency virus type 1 (HIV-1) into MVBs in macrophages has recently been visualized. The Gag proteins from HIV-1, as well as many other retroviruses, contain short motifs that mediate interactions with MVBs and other endocytic components, suggesting that Gag proteins directly interface with the endocytic pathway. Here, we show that HIV-1 Gag contains an internalization signal that promotes endocytosis of a chimeric transmembrane fusion protein. Mutation of this motif within Gag strongly inhibits virus-like particle production. Moreover, wild-type Gag, but not the internalization-defective mutation, can be induced to accumulate within CD63-positive MVBs by treatment of cells with U18666A, a drug that redistributes cholesterol from the plasma membrane to MVBs. We propose that HIV-1 Gag contains a signal that promotes interaction with the cellular endocytic machinery and that the site of particle production is regulated by the subcellular distribution of cholesterol.

scholarly journals Human Immunodeficiency Virus Type 1 Matrix Inhibits and Confers Cooperativity on Gag Precursor-Membrane Interactions

2004 ◽  
Vol 78 (17) ◽  
pp. 9560-9563 ◽  
Author(s):  
David Perez-Caballero ◽  
Theodora Hatziioannou ◽  
Juan Martin-Serrano ◽  
Paul D. Bieniasz
Keyword(s):  
Human Immunodeficiency Virus ◽  
Plasma Membrane ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Specific Targeting ◽  
Immunodeficiency Virus ◽  
Targeting Signal ◽  
Hiv 1 ◽  
Globular Head

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Gag multimerization and membrane binding are required for particle formation. However, it is unclear what constitutes a minimal plasma membrane-specific targeting signal and what role the matrix (MA) globular head and other Gag domains play in membrane targeting. Here, we use membrane flotation and microscopic analysis of Gag deletion mutants to demonstrate that the HIV-1 MA globular head inhibits a plasma membrane-specific targeting signal contained within the six amino-terminal MA residues. MA-mediated inhibition is relieved by concentration-dependent Gag multimerization and imparts a high degree of cooperativity on Gag-membrane association. This cooperativity may confer temporal and spatial regulation on HIV-1 assembly.

scholarly journals Vpu and Tsg101 Regulate Intracellular Targeting of the Human Immunodeficiency Virus Type 1 Core Protein Precursor Pr55gag

2006 ◽  
Vol 80 (8) ◽  
pp. 3765-3772 ◽  
Author(s):  
Kirsi Harila ◽  
Ian Prior ◽  
Mathilda Sjöberg ◽  
Antti Salminen ◽  
Jorma Hinkula ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Plasma Membrane ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Core Protein ◽  
Virus Assembly ◽  
Host Protein ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Assembly of human immunodeficiency virus type 1 (HIV-1) is directed by the viral core protein Pr55 gag . Depending on the cell type, Pr55 gag accumulates either at the plasma membrane or on late endosomes/multivesicular bodies. Intracellular localization of Pr55 gag determines the site of virus assembly, but molecular mechanisms that define cell surface or endosomal targeting of Pr55 gag are poorly characterized. We have analyzed targeting of newly synthesized Pr55 gag in HeLa H1 cells by pulse-chase studies and subcellular fractionations. Our results indicated that Pr55 gag was inserted into the plasma membrane and, when coexpressed with the viral accessory protein Vpu, Pr55 gag remained at the plasma membrane and virions assembled at this site. In contrast, Pr55 gag expressed in the absence of Vpu was initially inserted into the plasma membrane, but subsequently endocytosed, and virus assembly was partially shifted to internal membranes. This endocytosis of Pr55 gag required the host protein Tsg101. These results identified a previously unknown role for Vpu and Tsg101 as regulators for the endocytic uptake of Pr55 gag and suggested that the site of HIV-1 assembly is determined by factors that regulate the endocytosis of Pr55 gag .

scholarly journals Human Immunodeficiency Virus Type 1 Assembly, Budding, and Cell-Cell Spread in T Cells Take Place in Tetraspanin-Enriched Plasma Membrane Domains

2007 ◽  
Vol 81 (15) ◽  
pp. 7873-7884 ◽  
Author(s):  
Clare Jolly ◽  
Quentin J. Sattentau
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Plasma Membrane ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Membrane Domains ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Cell Cell

ABSTRACT Human immunodeficiency virus type-1 (HIV-1) egress from infected CD4+ T cells is thought to be via assembly and budding at the plasma membrane and may involve components of the T-cell secretory apparatus, including tetraspanins. However, many studies on HIV-1 assembly have examined the trafficking of viral proteins in isolation, and most have used immortalized epithelial, fibroblastic, or hematopoietic cell lines that may not necessarily reflect natural infection of susceptible T cells. Here we have used immunofluorescence and cryoimmunoelectron microscopy (CEM) to examine protein transport during HIV-1 assembly in productively infected Jurkat CD4+ T cells and primary CD4+ T cells. The HIV-1 envelope glycoprotein (Env) and the core protein (Gag) colocalize strongly with CD63 and CD81 and less strongly with CD9, whereas no colocalization was seen between Env or Gag and the late endosome/lysosomal marker Lamp2. CEM revealed incorporation of CD63 and CD81 but not Lamp2 into virions budding at the plasma membrane, and this was supported by immunoprecipitation studies, confirming that HIV-1 egress in T cells is trafficked via tetraspanin-enriched membrane domains (TEMs) that are distinct from lysosomal compartments. CD63, CD81, and, to a lesser extent, CD9 were recruited to the virological synapse (VS), and antibodies against these tetraspanins reduced VS formation. We propose that HIV-1 promotes virus assembly and cell-cell transfer in T cells by targeting plasma membrane TEMs.

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