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Saurav S, Tanwar J, Ahuja K, Motiani RK. Dysregulation of host cell calcium signaling during viral infections: Emerging paradigm with high clinical relevance. Mol Aspects Med 2021; 81:101004. [PMID: 34304899 PMCID: PMC8299155 DOI: 10.1016/j.mam.2021.101004] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 05/18/2021] [Accepted: 07/16/2021] [Indexed: 12/22/2022]
Abstract
Viral infections are one of the leading causes of human illness. Viruses take over host cell signaling cascades for their replication and infection. Calcium (Ca2+) is a versatile and ubiquitous second messenger that modulates plethora of cellular functions. In last two decades, a critical role of host cell Ca2+ signaling in modulating viral infections has emerged. Furthermore, recent literature clearly implicates a vital role for the organellar Ca2+ dynamics (influx and efflux across organelles) in regulating virus entry, replication and severity of the infection. Therefore, it is not surprising that a number of viral infections including current SARS-CoV-2 driven COVID-19 pandemic are associated with dysregulated Ca2+ homeostasis. The focus of this review is to first discuss the role of host cell Ca2+ signaling in viral entry, replication and egress. We further deliberate on emerging literature demonstrating hijacking of the host cell Ca2+ dynamics by viruses. In particular, a variety of viruses including SARS-CoV-2 modulate lysosomal and cytosolic Ca2+ signaling for host cell entry and replication. Moreover, we delve into the recent studies, which have demonstrated the potential of several FDA-approved drugs targeting Ca2+ handling machinery in inhibiting viral infections. Importantly, we discuss the prospective of targeting intracellular Ca2+ signaling for better management and treatment of viral pathogenesis including COVID-19. Finally, we highlight the key outstanding questions in the field that demand critical and timely attention.
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Affiliation(s)
- Suman Saurav
- Laboratory of Calciomics and Systemic Pathophysiology, Regional Centre for Biotechnology (RCB), Faridabad-121001, Delhi-NCR, India
| | - Jyoti Tanwar
- CSIR-Institute of Genomics and Integrative Biology (IGIB), New Delhi-110025, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India
| | - Kriti Ahuja
- Laboratory of Calciomics and Systemic Pathophysiology, Regional Centre for Biotechnology (RCB), Faridabad-121001, Delhi-NCR, India
| | - Rajender K Motiani
- Laboratory of Calciomics and Systemic Pathophysiology, Regional Centre for Biotechnology (RCB), Faridabad-121001, Delhi-NCR, India.
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Almeida C. A potential third-order role of the host endoplasmic reticulum as a contact site in interkingdom microbial endosymbiosis and viral infection. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:255-271. [PMID: 33559322 DOI: 10.1111/1758-2229.12938] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
The normal functioning of eukaryotic cells depends on the compartmentalization of metabolic processes within specific organelles. Interactions among organelles, such as those between the endoplasmic reticulum (ER) - considered the largest single structure in eukaryotic cells - and other organelles at membrane contact sites (MCSs) have also been suggested to trigger synergisms, including intracellular immune responses against pathogens. In addition to the ER-endogenous functions and ER-organelle MCSs, we present the perspective of a third-order role of the ER as a host contact site for endosymbiotic microbial non-pathogens and pathogens, from endosymbiont bacteria to parasitic protists and viruses. Although understudied, ER-endosymbiont interactions have been observed in a range of eukaryotic hosts, including protists, plants, algae, and metazoans. Host ER interactions with endosymbionts could be an ER function built from ancient, conserved mechanisms selected for communicating with mutualistic endosymbionts in specific life cycle stages, and they may be exploited by pathogens and parasites. The host ER-'guest' interactome and traits in endosymbiotic biology are briefly discussed. The acknowledgment and understanding of these possible mechanisms might reveal novel evolutionary perspectives, uncover the causes of unexplained cellular disorders and suggest new pharmacological targets.
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Affiliation(s)
- Celso Almeida
- ENDOBIOS Biotech®, Praceta Progresso Clube n° 6, 2725-110 Mem-Martins, Portugal
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3
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Host Calcium Channels and Pumps in Viral Infections. Cells 2019; 9:cells9010094. [PMID: 31905994 PMCID: PMC7016755 DOI: 10.3390/cells9010094] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 12/23/2019] [Accepted: 12/24/2019] [Indexed: 11/29/2022] Open
Abstract
Ca2+ is essential for virus entry, viral gene replication, virion maturation, and release. The alteration of host cells Ca2+ homeostasis is one of the strategies that viruses use to modulate host cells signal transduction mechanisms in their favor. Host calcium-permeable channels and pumps (including voltage-gated calcium channels, store-operated channels, receptor-operated channels, transient receptor potential ion channels, and Ca2+-ATPase) mediate Ca2+ across the plasma membrane or subcellular organelles, modulating intracellular free Ca2+. Therefore, these Ca2+ channels or pumps present important aspects of viral pathogenesis and virus–host interaction. It has been reported that viruses hijack host calcium channels or pumps, disturbing the cellular homeostatic balance of Ca2+. Such a disturbance benefits virus lifecycles while inducing host cells’ morbidity. Evidence has emerged that pharmacologically targeting the calcium channel or calcium release from the endoplasmic reticulum (ER) can obstruct virus lifecycles. Impeding virus-induced abnormal intracellular Ca2+ homeostasis is becoming a useful strategy in the development of potent antiviral drugs. In this present review, the recent identified cellular calcium channels and pumps as targets for virus attack are emphasized.
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Wei W, Huang W, Yue J. Requirement of IP3 receptor 3 (IP3R3) in nitric oxide induced cardiomyocyte differentiation of mouse embryonic stem cells. Exp Cell Res 2016; 346:9-16. [PMID: 27349290 DOI: 10.1016/j.yexcr.2016.06.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 06/21/2016] [Accepted: 06/23/2016] [Indexed: 01/29/2023]
Abstract
Nitric oxide (NO) markedly induces cardiomyocyte (CM) differentiation of embryonic stem (ES) cells. Here we examined the role of the Ca(2+) signaling in the NO-induced CM differentiation of mouse ES cells. We found that NO induced intracellular Ca(2+) increases in ES cells in a dose-dependent manner, and application of IP3 pathway antagonists not only significantly inhibited this induced Ca(2+) increase but also abolished NO-induced CM differentiation of ES cells. Subsequently, all 3 types of inositol 1, 4, 5-trisphosphate (IP3) receptors (IP3Rs) in mouse ES cells were individually or triply knocked down. Interestingly, only knockdown of type 3 IP3R (IP3R3) or triple-knockdown of three types of IP3Rs significantly inhibited the NO-induced Ca(2+) increases. Consistently, IP3R3 knockdown blocked the NO-induced CM differentiation of ES cells. CMs derived from IP3R3 knockdown ES cells also showed both structural and functional defects. In summary, our results indicate that the IP3R3-Ca(2+) pathway is required for NO-induced CM differentiation of ES cells.
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Affiliation(s)
- Wenjie Wei
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China; Department of Biology, South University of Science and Technology of China, Shenzhen 518052, China
| | - Wei Huang
- Department of Biology, South University of Science and Technology of China, Shenzhen 518052, China
| | - Jianbo Yue
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China.
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Ravindran MS, Bagchi P, Cunningham CN, Tsai B. Opportunistic intruders: how viruses orchestrate ER functions to infect cells. Nat Rev Microbiol 2016; 14:407-420. [PMID: 27265768 PMCID: PMC5272919 DOI: 10.1038/nrmicro.2016.60] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Viruses exploit the functions of the endoplasmic reticulum (ER) to promote both early and later stages of their life cycle, including entry, translation, replication, assembly, morphogenesis and egress. This observation reveals a shared principle that underlies virus–host cell relationships. Viral entry often requires disassembly of the incoming virus particle. This is best exemplified in the case of polyomavirus entry, in which ER-associated machineries are hijacked to disassemble the virus and promote entry to the cytosol en route to the nucleus. Many enveloped viruses, such as HIV and influenza virus, co-opt the ER-associated protein biosynthetic machinery to translate their genome and produce structural proteins that are necessary for the formation of virus particles and non-structural proteins that are essential during genome replication. Replication of the viral genome, particularly for positive-sense RNA ((+)RNA) viruses including hepatitis C virus (HCV), dengue virus (DENV) and West Nile virus (WNV), occurs in virus-induced membranous structures that are most often derived from the ER. The formation of these structures requires morphological changes to the ER membrane, involving membrane rearrangements that are induced by viral non-structural proteins that are targeted to the ER. As virus assembly is often coupled to genome replication, the assembly process frequently relies on the ER membrane. This strategy is seen for both RNA and DNA viruses. Morphogenesis of assembled virus particles can also take advantage of the ER. This is best observed in the non-enveloped rotavirus, for which a transient enveloped intermediate is converted to the mature and infectious particle in the lumen of the ER. After maturation in the ER, progeny virus particles egress the host through the ER-dependent secretory pathway, which provides a physical conduit to the extracellular environment. The overall observations that the ER actively promotes all steps of viral infection have therapeutic implications. The development of chemical inhibitors of selective ER-associated components is emerging as a potential avenue of antiviral therapy, provided that these inhibitors have minimal toxicity to the host cell.
Many host structures are vital for viral infection and the endoplasmic reticulum (ER), in particular, is essential. In this Review, Tsai and colleagues highlight examples of subversion of the ER by diverse viruses to promote all stages of their life cycle, from entry to egress. Viruses subvert the functions of their host cells to replicate and form new viral progeny. The endoplasmic reticulum (ER) has been identified as a central organelle that governs the intracellular interplay between viruses and hosts. In this Review, we analyse how viruses from vastly different families converge on this unique intracellular organelle during infection, co-opting some of the endogenous functions of the ER to promote distinct steps of the viral life cycle from entry and replication to assembly and egress. The ER can act as the common denominator during infection for diverse virus families, thereby providing a shared principle that underlies the apparent complexity of relationships between viruses and host cells. As a plethora of information illuminating the molecular and cellular basis of virus–ER interactions has become available, these insights may lead to the development of crucial therapeutic agents.
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Affiliation(s)
- Madhu Sudhan Ravindran
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, Room 3043, Ann Arbor, Michigan 48109, USA
| | - Parikshit Bagchi
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, Room 3043, Ann Arbor, Michigan 48109, USA
| | - Corey Nathaniel Cunningham
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, Room 3043, Ann Arbor, Michigan 48109, USA
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, Room 3043, Ann Arbor, Michigan 48109, USA
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Identification of Host Cell Factors Associated with Astrovirus Replication in Caco-2 Cells. J Virol 2015; 89:10359-70. [PMID: 26246569 DOI: 10.1128/jvi.01225-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 07/28/2015] [Indexed: 01/25/2023] Open
Abstract
UNLABELLED Astroviruses are small, nonenveloped viruses with a single-stranded positive-sense RNA genome causing acute gastroenteritis in children and immunocompromised patients. Since positive-sense RNA viruses have frequently been found to replicate in association with membranous structures, in this work we characterized the replication of the human astrovirus serotype 8 strain Yuc8 in Caco-2 cells, using density gradient centrifugation and free-flow zonal electrophoresis (FFZE) to fractionate cellular membranes. Structural and nonstructural viral proteins, positive- and negative-sense viral RNA, and infectious virus particles were found to be associated with a distinct population of membranes separated by FFZE. The cellular proteins associated with this membrane population in infected and mock-infected cells were identified by tandem mass spectrometry. The results indicated that membranes derived from multiple cell organelles were present in the population. Gene ontology and protein-protein interaction network analysis showed that groups of proteins with roles in fatty acid synthesis and ATP biosynthesis were highly enriched in the fractions of this population in infected cells. Based on this information, we investigated by RNA interference the role that some of the identified proteins might have in the replication cycle of the virus. Silencing of the expression of genes involved in cholesterol (DHCR7, CYP51A1) and fatty acid (FASN) synthesis, phosphatidylinositol (PI4KIIIβ) and inositol phosphate (ITPR3) metabolism, and RNA helicase activity (DDX23) significantly decreased the amounts of Yuc8 genomic and antigenomic RNA, synthesis of the structural protein VP90, and virus yield. These results strongly suggest that astrovirus RNA replication and particle assembly take place in association with modified membranes potentially derived from multiple cell organelles. IMPORTANCE Astroviruses are common etiological agents of acute gastroenteritis in children and immunocompromised patients. More recently, they have been associated with neurological diseases in mammals, including humans, and are also responsible for different pathologies in birds. In this work, we provide evidence that astrovirus RNA replication and virus assembly occur in contact with cell membranes potentially derived from multiple cell organelles and show that membrane-associated cellular proteins involved in lipid metabolism are required for efficient viral replication. Our findings provide information to enhance our knowledge of astrovirus biology and provide information that might be useful for the development of therapeutic interventions to prevent virus replication.
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Galbraith DA, Yang X, Niño EL, Yi S, Grozinger C. Parallel epigenomic and transcriptomic responses to viral infection in honey bees (Apis mellifera). PLoS Pathog 2015; 11:e1004713. [PMID: 25811620 PMCID: PMC4374888 DOI: 10.1371/journal.ppat.1004713] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 01/28/2015] [Indexed: 01/07/2023] Open
Abstract
Populations of honey bees are declining throughout the world, with US beekeepers losing 30% of their colonies each winter. Though multiple factors are driving these colony losses, it is increasingly clear that viruses play a major role. However, information about the molecular mechanisms mediating antiviral immunity in honey bees is surprisingly limited. Here, we examined the transcriptional and epigenetic (DNA methylation) responses to viral infection in honey bee workers. One-day old worker honey bees were fed solutions containing Israeli Acute Paralysis Virus (IAPV), a virus which causes muscle paralysis and death and has previously been associated with colony loss. Uninfected control and infected, symptomatic bees were collected within 20-24 hours after infection. Worker fat bodies, the primary tissue involved in metabolism, detoxification and immune responses, were collected for analysis. We performed transcriptome- and bisulfite-sequencing of the worker fat bodies to identify genome-wide gene expression and DNA methylation patterns associated with viral infection. There were 753 differentially expressed genes (FDR<0.05) in infected versus control bees, including several genes involved in epigenetic and antiviral pathways. DNA methylation status of 156 genes (FDR<0.1) changed significantly as a result of the infection, including those involved in antiviral responses in humans. There was no significant overlap between the significantly differentially expressed and significantly differentially methylated genes, and indeed, the genomic characteristics of these sets of genes were quite distinct. Our results indicate that honey bees have two distinct molecular pathways, mediated by transcription and methylation, that modulate protein levels and/or function in response to viral infections.
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Affiliation(s)
- David A. Galbraith
- Department of Entomology, Center for Pollinator Research, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Xingyu Yang
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Elina Lastro Niño
- Department of Entomology, Center for Pollinator Research, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Soojin Yi
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Christina Grozinger
- Department of Entomology, Center for Pollinator Research, Pennsylvania State University, University Park, Pennsylvania, United States of America
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8
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Brown SA, Loew LM. Integration of modeling with experimental and clinical findings synthesizes and refines the central role of inositol 1,4,5-trisphosphate receptor 1 in spinocerebellar ataxia. Front Neurosci 2015; 8:453. [PMID: 25653583 PMCID: PMC4300941 DOI: 10.3389/fnins.2014.00453] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 12/22/2014] [Indexed: 12/22/2022] Open
Abstract
A suite of models was developed to study the role of inositol 1,4,5-trisphosphate receptor 1 (IP3R1) in spinocerebellar ataxias (SCAs). Several SCAs are linked to reduced abundance of IP3R1 or to supranormal sensitivity of the receptor to activation by its ligand inositol 1,4,5-trisphosphate (IP3). Detailed multidimensional models have been created to simulate biochemical calcium signaling and membrane electrophysiology in cerebellar Purkinje neurons. In these models, IP3R1-mediated calcium release is allowed to interact with ion channel response on the cell membrane. Experimental findings in mice and clinical observations in humans provide data input for the models. The SCA modeling suite helps interpret experimental results and provides suggestions to guide experiments. The models predict IP3R1 supersensitivity in SCA1 and compensatory mechanisms in SCA1, SCA2, and SCA3. Simulations explain the impact of calcium buffer proteins. Results show that IP3R1-mediated calcium release activates voltage-gated calcium-activated potassium channels in the plasma membrane. The SCA modeling suite unifies observations from experiments in a number of SCAs. The cadre of simulations demonstrates the central role of IP3R1.
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Affiliation(s)
| | - Leslie M Loew
- Richard D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center Farmington, CT, USA
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9
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Mariani C, Desdouits M, Favard C, Benaroch P, Muriaux DM. Role of Gag and lipids during HIV-1 assembly in CD4(+) T cells and macrophages. Front Microbiol 2014; 5:312. [PMID: 25009540 PMCID: PMC4069574 DOI: 10.3389/fmicb.2014.00312] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 06/08/2014] [Indexed: 12/25/2022] Open
Abstract
HIV-1 is an RNA enveloped virus that preferentially infects CD4+ T lymphocytes and also macrophages. In CD4+ T cells, HIV-1 mainly buds from the host cell plasma membrane. The viral Gag polyprotein targets the plasma membrane and is the orchestrator of the HIV assembly as its expression is sufficient to promote the formation of virus-like particles carrying a lipidic envelope derived from the host cell membrane. Certain lipids are enriched in the viral membrane and are thought to play a key role in the assembly process and the envelop composition. A large body of work performed on infected CD4+ T cells has provided important knowledge about the assembly process and the membrane virus lipid composition. While HIV assembly and budding in macrophages is thought to follow the same general Gag-driven mechanism as in T-lymphocytes, the HIV cycle in macrophage exhibits specific features. In these cells, new virions bud from the limiting membrane of seemingly intracellular compartments, where they accumulate while remaining infectious. These structures are now often referred to as Virus Containing Compartments (VCCs). Recent studies suggest that VCCs represent intracellularly sequestered regions of the plasma membrane, but their precise nature remains elusive. The proteomic and lipidomic characterization of virions produced by T cells or macrophages has highlighted the similarity between their composition and that of the plasma membrane of producer cells, as well as their enrichment in acidic lipids, some components of raft lipids and in tetraspanin-enriched microdomains. It is likely that Gag promotes the coalescence of these components into an assembly platform from which viral budding takes place. How Gag exactly interacts with membrane lipids and what are the mechanisms involved in the interaction between the different membrane nanodomains within the assembly platform remains unclear. Here we review recent literature regarding the role of Gag and lipids on HIV-1 assembly in CD4+ T cells and macrophages.
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Affiliation(s)
- Charlotte Mariani
- Membrane Domains and Viral Assembly, CNRS UMR-5236, Centre d'étude d'agents Pathogènes et Biotechnologies pour la Santé Montpellier, Cedex, France
| | - Marion Desdouits
- Intracellular Transport and Immunity, Immunité et Cancer, Institut Curie - Inserm U932 Paris, France
| | - Cyril Favard
- Membrane Domains and Viral Assembly, CNRS UMR-5236, Centre d'étude d'agents Pathogènes et Biotechnologies pour la Santé Montpellier, Cedex, France
| | - Philippe Benaroch
- Intracellular Transport and Immunity, Immunité et Cancer, Institut Curie - Inserm U932 Paris, France
| | - Delphine M Muriaux
- Membrane Domains and Viral Assembly, CNRS UMR-5236, Centre d'étude d'agents Pathogènes et Biotechnologies pour la Santé Montpellier, Cedex, France
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10
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Ehrlich LS, Medina GN, Photiadis S, Whittredge PB, Watanabe S, Taraska JW, Carter CA. Tsg101 regulates PI(4,5)P2/Ca(2+) signaling for HIV-1 Gag assembly. Front Microbiol 2014; 5:234. [PMID: 24904548 PMCID: PMC4033031 DOI: 10.3389/fmicb.2014.00234] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Accepted: 04/30/2014] [Indexed: 11/13/2022] Open
Abstract
Our previous studies identified the 1,4,5-inositol trisphosphate receptor (IP3R), a channel mediating release of Ca2+ from ER stores, as a cellular factor differentially associated with HIV-1 Gag that might facilitate ESCRT function in virus budding. Channel opening requires activation that is initiated by binding of 1,4,5-triphosphate (IP3), a product of phospholipase C (PLC)-mediated PI(4,5)P2 hydrolysis. The store emptying that follows stimulates store refilling which requires intact PI(4,5)P2. Raising cytosolic Ca2+ promotes viral particle production and our studies indicate that IP3R and the ER Ca2+ store are the physiological providers of Ca2+ for Gag assembly and release. Here, we show that Gag modulates ER store gating and refilling. Cells expressing Gag exhibited a higher cytosolic Ca2+ level originating from the ER store than control cells, suggesting that Gag induced release of store Ca2+. This property required the PTAP motif in Gag that recruits Tsg101, an ESCRT-1 component. Consistent with cytosolic Ca2+ elevation, Gag accumulation at the plasma membrane was found to require continuous IP3R activation. Like other IP3R channel modulators, Gag was detected in physical proximity to the ER and to endogenous IP3R, as indicated respectively by total internal reflection fluorescence (TIRF) and immunoelectron microscopy (IEM) or indirect immunofluorescence. Reciprocal co-immunoprecipitation suggested that Gag and IP3R proximity is favored when the PTAP motif in Gag is intact. Gag expression was also accompanied by increased PI(4,5)P2 accumulation at the plasma membrane, a condition favoring store refilling capacity. Supporting this notion, Gag particle production was impervious to treatment with 2-aminoethoxydiphenyl borate, an inhibitor of a refilling coupling interaction. In contrast, particle production by a Gag mutant lacking the PTAP motif was reduced. We conclude that a functional PTAP L domain, and by inference Tsg101 binding, confers Gag with an ability to modulate both ER store Ca2+ release and ER store refilling.
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Affiliation(s)
- Lorna S Ehrlich
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Gisselle N Medina
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Sara Photiadis
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Paul B Whittredge
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health Bethesda, MD, USA
| | - Susan Watanabe
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Justin W Taraska
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health Bethesda, MD, USA
| | - Carol A Carter
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
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11
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Leyva-Grado VH, Hai R, Fernandes F, Belicha-Villanueva A, Carter C, Yondola MA. Modulation of an ectodomain motif in the influenza A virus neuraminidase alters tetherin sensitivity and results in virus attenuation in vivo. J Mol Biol 2013; 426:1308-21. [PMID: 24380762 DOI: 10.1016/j.jmb.2013.12.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 12/19/2013] [Accepted: 12/19/2013] [Indexed: 11/19/2022]
Abstract
We previously demonstrated that ectodomain residue Asp286 in N2 neuraminidase (NA; Asp268 in N1 NA) present in budding-capable NA proteins contributes to productive NA plasma membrane transport partly by mediating escape from tetherin restriction [Yondola MA, Fernandes F, Belicha-Villanueva A, Uccelini M, Gao Q, Carter C, et al. (2011). Budding capability of the influenza virus neuraminidase can be modulated by tetherin. J Virol, 85, 2480-2491]. Budding-incapable NA proteins contain a G at this position and either co-expression of human immunodeficiency virus type 1 vpu or siRNA-mediated depletion of tetherin rescued budding capabilities in these proteins [Yondola MA, Fernandes F, Belicha-Villanueva A, Uccelini M, Gao Q, Carter C, et al. (2011). Budding capability of the influenza virus neuraminidase can be modulated by tetherin. J Virol, 85, 2480-2491]. Furthermore, replacement of D286 with G in budding-capable NA proteins caused loss of function, preventing release of NA virus-like particles (VLPs). Here, we show that mutation of this residue specifically modulates the ability of NA to escape tetherin restriction at the plasma membrane and results in virus attenuation in vivo. Based on immunogold electron microscopy and co-immunoprecipitation assays, both NAD286-containing and NAD286G-containing proteins associated with tetherin in the endoplasmic reticulum (ER). However, the NAD286G loss-of-function mutant also associated with the host factor outside the ER and in plasma-membrane-localized VLPs as visualized using immunogold electron microscopy. We conclude that the presence of aspartate at residue 286 liberates NA from tetherin-dependent restriction upon exit from the ER compartment thus preventing restriction at the plasma membrane. Underscoring the importance of these observations, knockdown of tetherin resulted in a 1-1.5 log increase in influenza virus growth. Additionally, the loss-of-function mutation conferred attenuation in a mouse model of influenza infection as evidenced by a 5-fold increase in LD50 and increases in either percent survival or time to death dependent on the administered dose in vivo.
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Affiliation(s)
| | - Rong Hai
- Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | | | | | - Carol Carter
- Stony Brook University, Stony Brook, NY 11790, USA
| | - Mark A Yondola
- Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
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12
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Watanabe SM, Chen MH, Khan M, Ehrlich L, Kemal KS, Weiser B, Shi B, Chen C, Powell M, Anastos K, Burger H, Carter CA. The S40 residue in HIV-1 Gag p6 impacts local and distal budding determinants, revealing additional late domain activities. Retrovirology 2013; 10:143. [PMID: 24257210 PMCID: PMC3907034 DOI: 10.1186/1742-4690-10-143] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 11/11/2013] [Indexed: 12/11/2022] Open
Abstract
Background HIV-1 budding is directed primarily by two motifs in Gag p6 designated as late domain-1 and −2 that recruit ESCRT machinery by binding Tsg101 and Alix, respectively, and by poorly characterized determinants in the capsid (CA) domain. Here, we report that a conserved Gag p6 residue, S40, impacts budding mediated by all of these determinants. Results Whereas budding normally results in formation of single spherical particles ~100 nm in diameter and containing a characteristic electron-dense conical core, the substitution of Phe for S40, a change that does not alter the amino acids encoded in the overlapping pol reading frame, resulted in defective CA-SP1 cleavage, formation of strings of tethered particles or filopodia-like membrane protrusions containing Gag, and diminished infectious particle formation. The S40F-mediated release defects were exacerbated when the viral-encoded protease (PR) was inactivated or when L domain-1 function was disrupted or when budding was almost completely obliterated by the disruption of both L domain-1 and −2. S40F mutation also resulted in stronger Gag-Alix interaction, as detected by yeast 2-hybrid assay. Reducing Alix binding by mutational disruption of contact residues restored single particle release, implicating the perturbed Gag-Alix interaction in the aberrant budding events. Interestingly, introduction of S40F partially rescued the negative effects on budding of CA NTD mutations EE75,76AA and P99A, which both prevent membrane curvature and therefore block budding at an early stage. Conclusions The results indicate that the S40 residue is a novel determinant of HIV-1 egress that is most likely involved in regulation of a critical assembly event required for budding in the Tsg101-, Alix-, Nedd4- and CA N-terminal domain affected pathways.
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Affiliation(s)
- Susan M Watanabe
- Department of Molecular Genetics & Microbiology, Stony Brook University, Life Sciences Bldg, Rm 248, Stony Brook, NY 11794-5222, USA.
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13
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Spadaro F, Cecchetti S, Purificato C, Sabbatucci M, Podo F, Ramoni C, Gessani S, Fantuzzi L. Nuclear phosphoinositide-specific phospholipase C β1 controls cytoplasmic CCL2 mRNA levels in HIV-1 gp120-stimulated primary human macrophages. PLoS One 2013; 8:e59705. [PMID: 23555755 PMCID: PMC3610878 DOI: 10.1371/journal.pone.0059705] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 02/17/2013] [Indexed: 01/21/2023] Open
Abstract
HIV-1 envelope glycoprotein gp120 induces, independently of infection, the release of CCL2 from macrophages. In turn, this chemokine acts as an autocrine factor enhancing viral replication. In this study, we show for the first time that phosphoinositide-specific phospholipase C (PI-PLC) is required for the production of CCL2 triggered by gp120 in macrophages. Using a combination of confocal laser-scanner microscopy, pharmacologic inhibition, western blotting and fluorescence-activated cell sorter analysis, we demonstrate that gp120 interaction with CCR5 leads to nuclear localization of the PI-PLC β1 isozyme mediated by mitogen-activated protein kinase ERK-1/2. Notably, phosphatidylcholine-specific phospholipase C (PC-PLC), previously reported to be required for NF-kB-mediated CCL2 production induced by gp120 in macrophages, drives both ERK1/2 activation and PI-PLC β1 nuclear localization induced by gp120. PI-PLC β1 activation through CCR5 is also triggered by the natural chemokine ligand CCL4, but independently of ERK1/2. Finally, PI-PLC inhibition neither blocks gp120-mediated NF-kB activation nor overall accumulation of CCL2 mRNA, whereas it decreases CCL2 transcript level in the cytoplasm. These results identify nuclear PI-PLC β1 as a new intermediate in the gp120-triggered PC-PLC-driven signal transduction pathway leading to CCL2 secretion in macrophages. The finding that a concerted gp120-mediated signaling involving both PC- and PI-specific PLCs is required for the expression of CCL2 in macrophages suggests that this signal transduction pathway may also be relevant for the modulation of viral replication in these cells. Thus, this study may contribute to identify novel targets for therapeutic intervention in HIV-1 infection.
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Affiliation(s)
- Francesca Spadaro
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Serena Cecchetti
- Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy
| | - Cristina Purificato
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Michela Sabbatucci
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Franca Podo
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
- Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy
| | - Carlo Ramoni
- Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy
| | - Sandra Gessani
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Laura Fantuzzi
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
- * E-mail:
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14
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Defective HIV-1 particle assembly in AP-3-deficient cells derived from patients with Hermansky-Pudlak syndrome type 2. J Virol 2012; 86:11242-53. [PMID: 22875976 DOI: 10.1128/jvi.00544-12] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Adaptor protein complex 3 (AP-3) is a heterotetramer that is involved in signal-mediated protein sorting to endosomal-lysosomal organelles. AP-3 deficiency in humans, induced by mutations in the AP3B1 gene, which encodes the β3A subunit of the AP-3 complex, results in Hermansky-Pudlak syndrome 2 (HPS2), which is a rare genetic disorder with defective lysosome-related organelles. In a previous study, we identified the AP-3 complex as an important contributor to HIV-1 assembly and release. We hypothesized that cells from patients affected by HPS2 should demonstrate abnormalities of HIV-1 assembly. Here we report that HIV-1 particle assembly and release are indeed diminished in HPS2 fibroblast cultures. Transient or stable expression of the full-length wild-type β3A subunit in HPS2 fibroblasts restored the impaired virus assembly and release. In contrast, virus-like particle release mediated by MA-deficient Gag mutants lacking the AP-3 binding site was not altered in HPS2 cells, indicating that the MA domain serves as the major viral determinant required for the recruitment of the AP-3 complex. AP-3 deficiency decreased HIV-1 Gag localization at the plasma membrane and late endosomes and increased the accumulation of HIV-1 Gag at an intermediate step between early and late endosomes. Blockage of the clathrin-mediated endocytic pathway in HPS2 cells did not reverse the inhibited virus assembly and release imposed by the AP-3 deficiency. These results demonstrate that the intact and stable AP-3 complex is required for HIV-1 assembly and release, and the involvement of the AP-3 complex in late stages of the HIV-1 replication cycle is independent of clathrin-mediated endocytosis.
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15
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HIV Assembly and Budding: Ca(2+) Signaling and Non-ESCRT Proteins Set the Stage. Mol Biol Int 2012; 2012:851670. [PMID: 22761998 PMCID: PMC3384956 DOI: 10.1155/2012/851670] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 03/26/2012] [Indexed: 12/16/2022] Open
Abstract
More than a decade has elapsed since the link between the endosomal sorting complex required for transport (ESCRT) machinery and HIV-1 protein trafficking and budding was first identified. L domains in HIV-1 Gag mediate recruitment of ESCRT which function in bud abscission releasing the viral particle from the host cell. Beyond virus budding, the ESCRT machinery is also involved in the endocytic pathway, cytokinesis, and autophagy. In the past few years, the number of non-ESCRT host proteins shown to be required in the assembly process has also grown. In this paper, we highlight the role of recently identified cellular factors that link ESCRT machinery to calcium signaling machinery and we suggest that this liaison contributes to setting the stage for productive ESCRT recruitment and mediation of abscission. Parallel paradigms for non-ESCRT roles in virus budding and cytokinesis will be discussed.
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16
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Ehrlich LS, Medina GN, Carter CA. ESCRT machinery potentiates HIV-1 utilization of the PI(4,5)P(2)-PLC-IP3R-Ca(2+) signaling cascade. J Mol Biol 2011; 413:347-58. [PMID: 21875593 PMCID: PMC3193579 DOI: 10.1016/j.jmb.2011.08.038] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 08/05/2011] [Accepted: 08/16/2011] [Indexed: 01/09/2023]
Abstract
Human immunodeficiency virus type 1 (HIV-1) release efficiency is directed by late (L) domain motifs in the viral structural precursor polyprotein Gag, which serve as links to the ESCRT (endosomal sorting complex required for transport) machinery. Linkage is normally through binding of Tsg101, an ESCRT-1 component, to the P(7)TAP motif in the p6 region of Gag. In its absence, budding is directed by binding of Alix, an ESCRT adaptor protein, to the LY(36)PX(n)L motif in Gag. We recently showed that budding requires activation of the inositol 1,4,5-triphosphate receptor (IP3R), a protein that "gates" Ca(2+) release from intracellular stores, triggers Ca(2+) cell influx and thereby functions as a major regulator of Ca(2+) signaling. In the present study, we determined whether the L domain links Gag to Ca(2+) signaling machinery. Depletion of IP3R and inactivation of phospholipase C (PLC) inhibited budding whether or not Tsg101 was bound to Gag. PLC hydrolysis of phosphatidylinositol-(4,5)-bisphosphate generates inositol (1,4,5)-triphosphate, the ligand that activates IP3R. However, with Tsg101 bound, Gag release was independent of Gq-mediated activation of PLC, and budding was readily enhanced by pharmacological stimulation of PLC. Moreover, IP3R was redistributed to the cell periphery and cytosolic Ca(2+) was elevated, events indicative of induction of Ca(2+) signaling. The results suggest that L domain function, ESCRT machinery and Ca(2+) signaling are linked events in Gag release.
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Affiliation(s)
- Lorna S. Ehrlich
- Dept. of Molecular Genetics & Microbiology, Stony Brook University, Stony Brook, NY 11794-5222, USA
| | - Gisselle N. Medina
- Dept. of Molecular Genetics & Microbiology, Stony Brook University, Stony Brook, NY 11794-5222, USA
| | - Carol A. Carter
- Dept. of Molecular Genetics & Microbiology, Stony Brook University, Stony Brook, NY 11794-5222, USA
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17
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Chukkapalli V, Ono A. Molecular determinants that regulate plasma membrane association of HIV-1 Gag. J Mol Biol 2011; 410:512-24. [PMID: 21762797 DOI: 10.1016/j.jmb.2011.04.015] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 04/04/2011] [Accepted: 04/06/2011] [Indexed: 11/17/2022]
Abstract
Human immunodeficiency virus type 1 assembly is a multistep process that occurs at the plasma membrane (PM). Targeting and binding of Gag to the PM are the first steps in this assembly process and are mediated by the matrix domain of Gag. This review highlights our current knowledge on viral and cellular determinants that affect specific interactions between Gag and the PM. We will discuss potential mechanisms by which the matrix domain might integrate three regulatory components, myristate, phosphatidylinositol-(4,5)-bisphosphate, and RNA, to ensure that human immunodeficiency virus type 1 assembly occurs at the PM.
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Affiliation(s)
- Vineela Chukkapalli
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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18
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Abstract
Assembly and release of human immunodeficiency virus type 1 (HIV-1) particles is mediated by the viral Gag polyprotein precursor. Gag is synthesized in the cytosol and rapidly translocates to membrane to orchestrate particle production. The cell biology of HIV-1 Gag trafficking is currently one of the least understood aspects of HIV-1 replication. In this review, we highlight the current understanding of the cellular machinery involved in Gag trafficking and virus assembly.
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Affiliation(s)
- Muthukumar Balasubramaniam
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland
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19
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Ehrlich LS, Medina GN, Carter CA. Sprouty2 regulates PI(4,5)P2/Ca2+ signaling and HIV-1 Gag release. J Mol Biol 2011; 410:716-25. [PMID: 21762810 PMCID: PMC3139110 DOI: 10.1016/j.jmb.2011.04.069] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Revised: 04/26/2011] [Accepted: 04/27/2011] [Indexed: 12/13/2022]
Abstract
We reported recently that activation of the inositol 1,4,5-triphosphate receptor (IP3R) is required for efficient HIV-1 Gag trafficking and viral particle release. IP3R activation requires phospholipase C (PLC)-catalyzed hydrolysis of PI(4,5)P(2) to IP3 and diacylglycerol. We show that Sprouty2 (Spry2), which binds PI(4,5)P(2) and PLCγ, interfered with PI(4,5)P(2) in a manner similar to that of U73122, an inhibitor of PI(4,5)P(2) hydrolysis, suggesting that Spry2 negatively regulates IP3R by preventing formation of its activating ligand, IP3. Mutation to Asp of R252, a crucial determinant of PI(4,5)P(2) binding in the C-terminal domain of Spry2, prevented the interference, indicating that binding to the phospholipid is required. By contrast, deletion of the PLCγ binding region or mutation of a critical Tyr residue in the region did not prevent the interference but Spry2-PI(4,5)P(2) colocalization was not detected, suggesting that PLC binding is required for their stable association. Like U73122, Spry2 over-expression inhibited wild type Gag release as virus-like particles. Disrupting either binding determinant relieved the inhibition. IP3R-mediated Ca(2+)signaling, in turn, was found to influence Spry2 subcellular distribution and ERK, a Spry2 regulator. Our findings suggest that Spry2 influences IP3R function through control of PI(4,5)P(2) and IP3R influences Spry2 function by controlling its distribution and ERK activation.
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Affiliation(s)
- Lorna S Ehrlich
- Department of Molecular Genetics & Microbiology, Stony Brook University, Stony Brook, NY 11794-5222, USA
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20
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Joshi A, Garg H, Ablan SD, Freed EO. Evidence of a role for soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) machinery in HIV-1 assembly and release. J Biol Chem 2011; 286:29861-71. [PMID: 21680744 DOI: 10.1074/jbc.m111.241521] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Retrovirus assembly is a complex process that requires the orchestrated participation of viral components and host-cell factors. The concerted movement of different viral proteins to specific sites in the plasma membrane allows for virus particle assembly and ultimately budding and maturation of infectious virions. The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins constitute the minimal machinery that catalyzes the fusion of intracellular vesicles with the plasma membrane, thus regulating protein trafficking. Using siRNA and dominant negative approaches we demonstrate here that generalized disruption of the host SNARE machinery results in a significant reduction in human immunodeficiency virus type 1 (HIV-1) and equine infectious anemia virus particle production. Further analysis of the mechanism involved revealed a defect at the level of HIV-1 Gag localization to the plasma membrane. Our findings demonstrate for the first time a role of SNARE proteins in HIV-1 assembly and release, likely by affecting cellular trafficking pathways required for Gag transport and association with the plasma membrane.
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Affiliation(s)
- Anjali Joshi
- Center of Excellence for Infectious Diseases, Department of Biomedical Sciences, Texas Tech University Health Sciences Center, El Paso, Texas 79905, USA.
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Inositol 1,4,5-trisphosphate receptor subtype-specific regulation of calcium oscillations. Neurochem Res 2011; 36:1175-85. [PMID: 21479917 PMCID: PMC3111726 DOI: 10.1007/s11064-011-0457-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/18/2011] [Indexed: 11/18/2022]
Abstract
Oscillatory fluctuations in the cytosolic concentration of free calcium ions (Ca2+) are considered a ubiquitous mechanism for controlling multiple cellular processes. Inositol 1,4,5-trisphosphate (IP3) receptors (IP3R) are intracellular Ca2+ release channels that mediate Ca2+ release from endoplasmic reticulum (ER) Ca2+ stores. The three IP3R subtypes described so far exhibit differential structural, biophysical, and biochemical properties. Subtype specific regulation of IP3R by the endogenous modulators IP3, Ca2+, protein kinases and associated proteins have been thoroughly examined. In this article we will review the contribution of each IP3R subtype in shaping cytosolic Ca2+ oscillations.
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22
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Muriaux D, Darlix JL. Properties and functions of the nucleocapsid protein in virus assembly. RNA Biol 2010; 7:744-53. [PMID: 21157181 DOI: 10.4161/rna.7.6.14065] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
HIV-1 nucleocapsid protein (NC) is a small basic protein generated by the cleavage of the Gag structural polyprotein precusor by the viral protease during virus assembly in the infected cell. HIV-1 NC possesses two copies of a highly conserved CCHC zinc finger (ZnF), flanked by basic residues. HIV-1 NC and more generally retroviral NC proteins are nucleic acid binding proteins possessing potent nucleic acid condensing and chaperoning activities. As such NC protein drives critical structural rearrangements of the genomic RNA, notably RNA dimerization in the course of virus assembly and viral nucleic acid annealing required for genomic RNA replication by the viral reverse transcriptase (RT). Here we review the relationships between the 3D structure of HIV-1 NC, notably the central globular domain encompassing the two zinc fingers and the basic linker and NC functions in the early and late phases of virus replication. One of the salient feature of the NC central globular domain is an hydrophobic plateau which appears to orchestrate the NC functions, such as chaperoning the conversion of the genomic RNA into viral DNA by RT during the early phase, and driving the selection and dimerization of the genomic RNA at the initial stage of viral particle assembly. This ensures a bona fide trafficking of early GagNC-genomic RNA complexes to the plasma membrane of the infected cell and ultimately virion formation and budding.
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