Journal of Virology最新文献

{"title":"Primer: Functions and evolution of viral proteins.","authors":"Eugene V Koonin, Mart Krupovic","doi":"10.1128/jvi.01202-26","DOIUrl":"10.1128/jvi.01202-26","url":null,"abstract":"<p><p>Viruses encode an enormous variety of proteins that jointly comprise the largest pool of protein diversity on Earth. At coarse grain, the viral pan-proteome can be partitioned into four classes of proteins that differ in their evolutionary conservation, spread across the virosphere, and broadly defined functionality: (i) viral hallmark proteins (VHPs) that are broadly conserved across different realms of viruses, (ii) proteins responsible for core viral functions, such as replication, expression, and virion structure, but are more narrowly represented within a single virus realm, kingdom, or phylum, (iii) fast-evolving proteins involved in virus-host interactions, particularly counter-defense, that are typically conserved only in narrow groups of viruses, (iv) \"dark matter,\" that is, proteins without detectable homologs or known functions, typically shared only by closely related viruses. Apart from the few VHPs that might descend from the primordial protein pool, most of the viral proteins are derived from cellular ancestors, via recruitment of proteins with activities relevant for virus replication, and extensive exaptation. The recruitment of cellular proteins for roles in viral reproduction follows a logic dictated by the functionalities that are relevant for viruses. Thus, different groups of viruses often convergently capture distinct, sometimes unrelated proteins, providing similar activities, for example, polymerases, helicases, and proteases of different families. Recent advances in protein structure prediction and analysis provide unprecedented insights into the organization and evolution of the viral pan-proteome.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0120226"},"PeriodicalIF":4.1,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149181813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Primer: Giant viruses of protists.","authors":"Jonatas Santos Abrahao","doi":"10.1128/jvi.01257-26","DOIUrl":"10.1128/jvi.01257-26","url":null,"abstract":"<p><p>Giant viruses infecting protists have expanded our understanding of viral diversity. These members of the phylum <i>Nucleocytoviricota</i> possess genomes that can exceed 2.5 Mb and encode hundreds to thousands of proteins, including functions once thought unique to cellular organisms. They infect amoebae, algae, and other unicellular eukaryotes, forming large factories and interacting with virophages and mobile genetic elements. Their virions display diverse architectures, from icosahedral particles to amphora-shaped pandoraviruses and tail-bearing tupanviruses. Comparative genomics highlights evolutionary processes such as horizontal gene transfer, gene duplication, <i>de novo</i> gene birth, and genome rearrangements, which contribute to their genomic diversity. Despite their widespread presence in aquatic and terrestrial ecosystems, many aspects of their biology remain unknown, including the roles of lineage-specific ORFan genes (open reading frames with no detectable homologs in current databases) and the molecular strategies used to manipulate hosts. This Primer provides an accessible overview of protist-infecting giant viruses, summarizing their classification, virion architecture, replication strategies, and evolutionary scenarios, and points to key questions that remain open.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0125726"},"PeriodicalIF":4.1,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149181907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Beyond independent roles: spatiotemporal coupling between viral fusion proteins and viroporins in viral replication and host inflammation.","authors":"Jiaqi Li, Yuan Sun, Hua-Ji Qiu, Su Li","doi":"10.1128/jvi.01013-26","DOIUrl":"https://doi.org/10.1128/jvi.01013-26","url":null,"abstract":"<p><p>Membrane fusion and permeabilization are key membrane remodeling processes hijacked by viruses. Although fusion proteins and viroporins have long been characterized as discrete functional modules, emerging evidence supports the spatiotemporal coordination through shared regulation of ion flux, pH homeostasis, membrane tension, organelle stress, and vesicular trafficking during viral infections. These synchronized membrane events synergistically shape viral replication and host immune responses. This review establishes a fusion-ion-inflammation axis to guide mechanistic exploration and antiviral drug development.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0101326"},"PeriodicalIF":4.1,"publicationDate":"2026-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149182732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting mRNA capping in <i>Mononegavirales</i>: a promising, yet underexplored antiviral target.","authors":"Khadijah Khan, Mohammad Ejaz Adil, Monika Antil, Dilip Kumar","doi":"10.1128/jvi.01025-26","DOIUrl":"https://doi.org/10.1128/jvi.01025-26","url":null,"abstract":"<p><p>mRNA capping is a co-transcriptional, nuclear process in eukaryotes that adds a cap onto the 5' end of RNA to confer stability, efficient translation, and nuclear export. Viruses have evolved diverse strategies by mimicking or subverting host pathways to install an mRNA cap for efficient gene expression and evasion of the host innate immune response. The conventional mRNA capping pathway, employed by many RNA and DNA viruses, is mediated by dedicated RNA 5'-triphosphatase, guanylyltransferase, and methyltransferase enzymes. In contrast, many RNA viruses utilize unconventional capping mechanisms that diverge from the canonical pathway, offering unique opportunities to develop virus family-specific antiviral therapeutics. Among negative-sense RNA viruses, members of the order <i>Mononegavirales</i> harbor a unique capping domain, polyribonucleotidyltransferase (PRNTase), embedded within the viral RdRp large (L) protein. Unlike the conventional guanylyltransferase-mediated mechanism, PRNTase catalyzes mRNA capping through the formation of a covalent L-pRNA intermediate rather than the canonical GMP-enzyme intermediate. The HR motif in PRNTase, involved in covalent linking to mRNA, is highly conserved in non-segmented negative-strand RNA viruses. This review focuses on structural and functional insights into <i>Mononegavirales</i> capping, highlighting the conserved motifs and domain architecture that make it a promising therapeutic target.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0102526"},"PeriodicalIF":4.1,"publicationDate":"2026-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149182385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Avian influenza A virus polymerase gene leads to temperature-resistant genome replication.","authors":"Stephanie L Williams, Sebastian M Gygli, Jacob C Bjorgen, Haitian Fan, Munashe Mudiwa, Lex Matthews, Yongli Xiao, Ashley Freeman, Sharon F Legaspi, Li Qi, Jeffery K Taubenberger, Ervin Fodor","doi":"10.1128/jvi.00978-26","DOIUrl":"https://doi.org/10.1128/jvi.00978-26","url":null,"abstract":"<p><p>Influenza A viruses (IAV) pose a persistent pandemic threat. Successful cross-species transmission from waterfowl to mammals requires host adaptation for efficient replication and spread. Avian IAVs are adapted to the temperature of the avian gut, approximately 41°C, while human IAVs replicate at 33°C in the upper respiratory tract. PB1, the catalytic core of the viral heterotrimeric RNA-dependent RNA polymerase (RdRp), is essential for viral RNA synthesis. Three pandemic IAV strains (1918, 1957, and 1968) carried an avian-origin PB1 gene, suggesting a selective advantage. Fever, a critical antiviral response, elevates body temperature to 38°C or higher and can restrict viral replication. We hypothesized that avian PB1 may allow IAV replication at febrile temperatures. Using a mini-replicon system, we demonstrate that a polymerase of a seasonal human H1N1 IAV fails to replicate viral RNA efficiently at 40°C, whereas substitution of the PB1 with that from the 1918, 1957, and 1968 pandemic viruses, or a low-pathogenic avian H2N1 virus, restores RNA synthesis. Chimeric seasonal human H1N1 viruses expressing avian or 1918 PB1 replicate at 40°C in MDCK cells, unlike wild-type H1N1. Activity assays with purified chimeric IAV polymerases further suggest that avian-origin PB1 may intrinsically enhance polymerase activity at elevated temperatures. Together, these data show that avian-origin PB1 enables IAV replication at febrile temperatures, highlighting its role in zoonotic emergence and host adaptation. Surveillance of avian-origin PB1 genes in IAVs circulating in mammals may help identify strains with pandemic potential and inform the development of countermeasures.IMPORTANCEInfluenza A viruses of avian origin remain a persistent threat to human health. The 1918, 1957, and 1968 pandemic influenza viruses each acquired an avian-origin PB1 gene, but the adaptive advantage conferred by these genes remains incompletely understood. Here, we show that avian-origin PB1 genes enhance viral RNA replication by a seasonal human influenza virus polymerase at elevated temperature and enable replication of a human influenza virus at 40°C, a temperature relevant to both avian hosts and human febrile illness. PB1-dependent effects were observed in cell-based polymerase assays, with purified polymerase, and during authentic virus infection. These findings identify temperature-resistant genome replication as a potential adaptive property of avian-origin PB1 and suggest that acquisition of an avian PB1 may help influenza viruses overcome temperature barriers encountered during adaptation to mammalian hosts.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0097826"},"PeriodicalIF":4.1,"publicationDate":"2026-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149182721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Superinfection exclusion strategy of siphophage T5: analysis of the FhuA:Llp complex.","authors":"Séraphine Degroux, Corinne Vivès, Emeline Mestdach, Claudine Darnault, Aline le Roy, Caroline Mas, Loïc Salmon, Torsten Herrmann, Cécile Breyton","doi":"10.1128/jvi.00909-26","DOIUrl":"https://doi.org/10.1128/jvi.00909-26","url":null,"abstract":"<p><p>Superinfection exclusion is a widespread viral mechanism that protects the infected cell from overinfection by other identical or closely related viruses. Shortly after infection by bacteriophage T5, the bacterium <i>Escherichia coli</i> produces Llp, encoded by the newly injected viral genome. Llp is a small lipoprotein targeted to the inner leaflet of the host outer membrane. It binds to FhuA, an outer-membrane iron-ferrichrome transporter, which is the T5 receptor at the <i>E. coli</i> cell surface. The interaction between Llp and FhuA prevents any further bacteriophage binding and infection. Here, we determined the NMR structure of Llp and analyzed the formation of the FhuA:Llp complex using a wide range of techniques and mutants, both <i>in vivo</i> and <i>in vitro</i>. Interaction of Llp with FhuA is governed by a two-step equilibrium with a strong contribution of induced fit: Llp binding requires remodeling of FhuA periplasmic plug surface, enabling the subsequent large conformational reorganization of the extracellular loops. Analysis of FhuA mutants shows the importance of the intertwined interactions between the extracellular loops and the plug in the communication between the periplasmic and the extracellular faces of FhuA.IMPORTANCEBacteriophages (phages) are viruses that infect bacteria. As their enemies, phages play an important role in the dynamics, diversity, evolution, and pathogenicity of bacterial populations, but also represent an alternative to antibiotics in our fight against the rise of multi-resistant pathogenic bacterial strains. Infection is triggered by phage recognition of a receptor at the host surface, inducing phage DNA injection into the bacterial cytoplasm. The host cell is then transformed into a viral factory. To secure this viral factory, the infecting phage develops superinfection exclusion strategies, preventing other phages from interfering. Understanding how phages achieve the \"locking\" of the host will allow us to optimize phage use in phage therapy. Here, we analyze the structure of the receptor-exclusion protein complex using integrated <i>in vivo</i>, biochemical, and biophysical approaches. Our analysis reveals an unusually slow association process, consistent with an induced-fit mechanism, ultimately transmitting information from the bacterial periplasm to its surface.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0090926"},"PeriodicalIF":4.1,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149167220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Marek's disease virus: mechanistic insights into host immune responses and multilayered immune evasion strategies.","authors":"Kexin Gao, Qingqing Yu, Ru Guo, Huijing Sun, Yulu Duan, Yanping Zhang, Yulong Gao, Yongzhen Liu","doi":"10.1128/jvi.00736-26","DOIUrl":"https://doi.org/10.1128/jvi.00736-26","url":null,"abstract":"<p><p>Marek's disease virus (MDV) is a highly contagious, oncogenic alphaherpesvirus that induces profound immunosuppression and T-cell lymphomas in poultry, serving as a prominent paradigm for investigating virus-induced tumorigenesis and pathogen evolution under vaccine-driven selection pressure. Despite half a century of widespread vaccination, the continuous circulation and progressive enhancement of MDV virulence within flocks highlight a critical gap in our understanding of host-virus immunological interplay and co-evolution. This review systematically delineates the dynamic molecular mechanisms underlying the interplay between MDV and the host immune system. We first dissect the innate immune sensing networks, with a particular focus on the cGAS-STING pathway, and elucidate the multidimensional strategies employed by MDV to antagonize these early antiviral defenses. Subsequently, we explore the complexities of the adaptive immune response, revealing the immune evasion mechanisms by which MDV establishes a tumor-permissive microenvironment via the downregulation of MHC-I, induction of T-cell exhaustion, and recruitment of regulatory T cells. Furthermore, we discuss telomere integration as a key mechanism contributing to MDV persistence and highlight the unresolved mechanisms governing reactivation. The purpose of this review is to clarify the key factors that determine the immune protective efficacy of MDV vaccines and to provide insights into the optimization of prevention and control strategies.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0073626"},"PeriodicalIF":4.1,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149170007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"HSV-1 induces stable associations between the Golgi and endosomes within the cytoplasmic viral assembly compartment of neuronal cells.","authors":"Dah Hyun Jung, Shaowen White, Richard J Roller","doi":"10.1128/jvi.00999-26","DOIUrl":"https://doi.org/10.1128/jvi.00999-26","url":null,"abstract":"<p><p>Assembly of mature herpesvirus particles is associated with extensive rearrangement of cytoplasmic membranes. Herpes simplex virus type 1 (HSV-1) infection in neuronal cells induces the formation of a distinctive cytoplasmic viral assembly compartment (cVAC), in which rearranged host membranes and viral proteins are clustered at the perinuclear microtubule-organizing center (MTOC). Although both the <i>trans</i>-Golgi network (TGN) and endosomal compartments have been implicated as membrane sources for cytoplasmic envelopment, how secretory and endosomal pathways are reorganized and associated within the cVAC remains unclear. Here, we treated HSV-1-infected cells with nocodazole at a post-entry stage to disperse membrane components of the cVAC and identify microtubule-independent membrane organizations and associations using immunofluorescence imaging. We found that the Golgi apparatus was fragmented during infection but maintained cisternal stacking, as the Golgi markers GM130, GalT, and GRASP65 remained colocalized in both the absence and presence of nocodazole. We further demonstrated that Golgi mini-stacks retained their association with Rab6 during HSV-1 infection and formed microtubule-independent associations with early and recycling endosomes, resulting in the formation of Golgi-endosome super-mini-stacks. Viral capsid, glycoprotein, and tegument proteins were colocalized with Golgi-endosome super-mini-stacks in both the presence and absence of microtubules, suggesting that this membrane complex serves as a site of cytoplasmic envelopment regardless of clustering at the MTOC. Formation of these stable Golgi-endosome associations did not require viral capsids. Neither actin filaments nor acetylated microtubules colocalized with Golgi-endosome super-mini-stacks, suggesting that cytoskeletal elements are not required for this association.IMPORTANCEMany viruses remodel host cytoplasmic membranes to facilitate their assembly. Elucidating the molecular mechanisms underlying this remodeling may reveal novel antiviral targets while also providing insight into fundamental principles of intracellular membrane organization. Infection with an important human pathogen, herpes simplex virus type 1 (HSV-1), induces extensive membrane remodeling that leads to the formation of the cytoplasmic viral assembly compartment (cVAC) in neuronal cells, yet the underlying mechanisms remain poorly understood. Here, we demonstrate that HSV-1 induces stable associations between membranes within the cVAC. Our findings support a model in which HSV-1 generates a dynamic hybrid membrane compartment during infection, potentially reconciling conflicting views on the roles of distinct membrane sources in cytoplasmic assembly.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0099926"},"PeriodicalIF":4.1,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149170093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Syncrip coordinates with hnRNPK to regulate PPV NS1 mRNA splicing and facilitate viral replication.","authors":"Yiyuan Jiang, Qian Du, Xiaoyang Zhang, Liu Yang, Caiyi Chen, Bichen Miao, Yong Huang, Dewen Tong","doi":"10.1128/jvi.00901-26","DOIUrl":"https://doi.org/10.1128/jvi.00901-26","url":null,"abstract":"<p><p>Porcine parvovirus (PPV) relies on alternative splicing of the nonstructural protein 1 (NS1) transcript to generate nonstructural protein 2 (NS2), but the host factors coordinating this process remain incompletely defined. Here, we identified heterogeneous nuclear ribonucleoprotein K (hnRNPK) as a regulator of PPV NS1-to-NS2 mRNA splicing in PK-15 cells. hnRNPK specifically associated with NS1 mRNA, and PPV infection increased hnRNPK expression in a time- and multiplicity-of-infection-dependent manner. hnRNPK overexpression decreased the NS1/NS2 mRNA and protein ratios and increased viral DNA accumulation, whereas hnRNPK knockout produced the opposite effects. hnRNPK and the previously identified splicing regulator synaptotagmin-binding, cytoplasmic RNA-interacting protein (Syncrip) additively promoted NS1-to-NS2 splicing and PPV replication. Double-knockout and reconstitution experiments further showed that co-expression of hnRNPK and Syncrip restored NS2 production and viral replication more effectively than either factor alone. Domain-mapping analyses identified the K-protein interaction region (KI) of hnRNPK and the RNA recognition motif 2 (RRM2) region of Syncrip as the principal regions supporting this activity. hnRNPK associated directly with Syncrip, and Syncrip was required for efficient recruitment of hnRNPK to NS1 mRNA. In addition, hnRNPK associated with serine- and arginine-rich splicing factor 1 (SRSF1) in an RNA-independent manner during PPV infection. These findings support a model in which a Syncrip-hnRNPK complex promotes PPV NS1-to-NS2 alternative splicing and thereby facilitates viral replication, while identifying SRSF1 as a candidate component of the associated host splicing machinery.IMPORTANCEPorcine parvovirus (PPV) causes reproductive failure in swine and relies extensively on host RNA-processing machinery because of its limited coding capacity. Alternative splicing of the PPV nonstructural protein 1 (NS1) transcript generates nonstructural protein 2 (NS2), but the host factors controlling this process remain poorly defined. Here, we identify heterogeneous nuclear ribonucleoprotein K (hnRNPK) as a host regulator of PPV mRNA splicing and replication. hnRNPK acts additively with synaptotagmin-binding, cytoplasmic RNA-interacting protein (Syncrip) to promote NS1-to-NS2 mRNA splicing, increase NS2 production, and support viral DNA replication. Syncrip facilitates the association of hnRNPK with NS1 mRNA, and defined regions within both proteins contribute to this activity. hnRNPK also associates with the cellular splicing factor serine- and arginine-rich splicing factor 1 (SRSF1) during PPV infection. These findings reveal a host RNA-binding protein network that PPV exploits to expand its coding capacity and promote replication.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0090126"},"PeriodicalIF":4.1,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149172233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SERINC5 is the primary target of retroviral antagonists among human SERINC paralogs and requires a tri-cysteine motif for its counteraction by HIV-1 Nef.","authors":"Cinzia Bertelli, Annachiara Rosa, Teresa Vanzo, Irene Crescioli, Hamza Ur Rehman, Ajit Chande, Remigiusz Serwa, Edward W Tate, Peter Cherepanov, Massimo Pizzato","doi":"10.1128/jvi.01088-26","DOIUrl":"https://doi.org/10.1128/jvi.01088-26","url":null,"abstract":"<p><p>The human transmembrane protein SERINC5 incorporates into budding HIV-1 particles and inhibits virus fusion with target cells. Although three other human SERINC paralogs display antiviral activity, their contribution to retroviral restriction and their susceptibility to viral antagonists have not been systematically compared. HIV-1 Nef, Moloney murine leukemia virus (MoMLV) glycoGag, and the equine infectious anemia virus (EIAV) S2 glycoprotein independently evolved mechanisms to counteract SERINC5. Here, we show that all human SERINC paralogs are incorporated into HIV-1 virions despite their differing antiviral activities. However, compared with the other SERINC paralogs, SERINC5 is selectively and efficiently targeted by all retroviral antagonists examined, supporting the notion that SERINC5 has exerted the strongest selective pressure on retroviral evolution. We identified a tri-cysteine motif within intracellular loop 4 (ICL4) as a critical determinant of SERINC5 antagonism by Nef. Disruption of this motif impaired Nef-mediated internalization, exclusion from virions, and full rescue of HIV-1 infectivity by diverse HIV-1 and SIV Nef alleles, but had no effect on antagonism by MoMLV glycoGag or EIAV S2, indicating that these viral proteins recognize distinct molecular features of SERINC5. Transfer of ICL4 to SERINC2 was insufficient to confer Nef sensitivity, demonstrating that the tri-cysteine motif is necessary but not sufficient for antagonism. Finally, we show that this motif is palmitoylated, suggesting that palmitoylation contributes to SERINC5 recognition by Nef. Together, these findings establish SERINC5 as the principal target of retroviral antagonists and demonstrate that its recognition by Nef depends on the broader structural context of SERINC5.</p><p><strong>Importance: </strong>The SERINC family of multipass transmembrane proteins includes host factors capable of restricting retrovirus infectivity. Among the five human paralogs, SERINC5 displays the strongest antiviral activity and is the only member efficiently targeted by all known retroviral antagonists, including HIV-1 Nef, MLV glycoGag, and the EIAV S2. This selectivity indicates that the evolutionary pressure exerted by SERINC proteins on retroviruses has been primarily driven by SERINC5 rather than by its relatives. Through structure-guided mutagenesis, we identified a tri-cysteine motif within intracellular loop 4 as a crucial determinant for SERINC5 downregulation by Nef, providing a molecular explanation for its distinctive susceptibility. These findings establish SERINC5 as the principal target of viral counteraction and suggest that its molecular features have contributed to shaping the adaptation of primate lentiviral Nef proteins to the host.</p>","PeriodicalId":17583,"journal":{"name":"Journal of Virology","volume":" ","pages":"e0108826"},"PeriodicalIF":4.1,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149170716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}