GO:0019064 fusion of virus membrane with host plasma membrane: Viral Entry Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0019064 describes the fusion of a viral membrane with the host cell plasma membrane during viral entry, releasing virion contents into the cytoplasm.
• This process is used by enveloped viruses such as influenza virus, SARS-CoV-2, and alphaherpesviruses to initiate infection.
• Fusion requires viral fusion proteins, often activated by receptor binding or proteolytic cleavage, and can occur at the plasma membrane or after endocytosis.
• Key viral proteins include influenza hemagglutinin, SARS-CoV-2 spike, and herpes simplex virus glycoproteins gB, gD, gH/gL.
• Host factors such as IFITM3 can restrict fusion by altering lipid ordering and stabilizing hemifusion intermediates.
• Studying GO:0019064 informs antiviral drug development, vaccine design, and understanding of viral pathogenesis.
Description
Fusion of the viral membrane with the host plasma membrane is a critical step in the entry of enveloped viruses, allowing the viral genome to be delivered into the host cell cytoplasm. This process, annotated as GO:0019064, is essential for infection by many clinically important viruses, including influenza virus, coronaviruses, and herpesviruses. Understanding the molecular details of this fusion event is fundamental for developing antiviral therapies and vaccines. The fusion reaction is mediated by viral fusion proteins that undergo conformational changes triggered by receptor binding, low pH, or proteolytic cleavage, leading to the merger of viral and cellular membranes. Research on this process has been accelerated by advanced imaging techniques such as single-virus tracking, which can resolve the dynamics of fusion at the plasma membrane. Moreover, host restriction factors like IFITM3 can block fusion by modulating membrane lipid composition and stabilizing hemifusion intermediates, highlighting the interplay between viral and host factors. This article provides a comprehensive overview of GO:0019064, covering its definition, mechanism, key genes, disease relevance, and experimental approaches for studying it.
fusion of virus membrane with host plasma membrane At A Glance
| GO ID | GO:0019064 |
|---|---|
| GO term | fusion of virus membrane with host plasma membrane |
| Ontology | biological_process |
| Synonym | viral envelope fusion; viral penetration via membrane fusion; viral entry into host cell via membrane fusion with the plasma membrane |
| Major function | Mediates the merger of viral and host plasma membranes to release viral contents into the cytoplasm during entry of enveloped viruses |
| Definition | Fusion of a viral membrane with the host cell membrane during viral entry. Results in release of the virion contents into the cytoplasm. |
| Related processes | Viral entry, membrane fusion, endocytosis, hemifusion |
| Key viral proteins | Influenza hemagglutinin, SARS-CoV-2 spike, herpes simplex virus glycoproteins gB, gD, gH/gL |
| Host factors | IFITM3, lipid rafts, cholesterol, proteases |
What Is GO:0019064?
GO:0019064, fusion of virus membrane with host plasma membrane, is a biological process defined as the fusion of a viral membrane with the host cell membrane during viral entry, resulting in the release of virion contents into the cytoplasm. This term specifically refers to fusion events that occur at the plasma membrane, as opposed to fusion within endosomes, although some viruses can fuse at either location depending on conditions. The process is synonymous with viral envelope fusion, viral penetration via membrane fusion, and viral entry into host cell via membrane fusion with the plasma membrane.
Why Is fusion of virus membrane with host plasma membrane Important in Cell Biology?
GO:0019064 is a central step in the life cycle of enveloped viruses and represents a prime target for antiviral intervention. Because fusion is required for the release of the viral genome into the host cell, blocking this process can prevent infection. Many approved and experimental antiviral drugs, such as fusion inhibitors for HIV and SARS-CoV-2, act by interfering with membrane fusion. Additionally, understanding the molecular mechanisms of fusion informs vaccine design, as antibodies that neutralize fusion proteins can be protective. The process is also relevant to viral pathogenesis, as differences in fusion efficiency and host restriction factors like IFITM3 can influence viral tropism and disease severity.
• Essential for entry of enveloped viruses including influenza, SARS-CoV-2, and herpesviruses.
• Target for antiviral drugs such as fusion inhibitors.
• Informs vaccine development by identifying neutralizing epitopes on fusion proteins.
• Host restriction factors like IFITM3 modulate fusion and influence viral susceptibility.
• Fusion mechanisms can be exploited for gene delivery and cell-cell fusion studies.
• Single-virus tracking provides quantitative insights into fusion dynamics.
• Dysregulation of fusion can lead to syncytia formation and tissue damage in viral infections.
• Understanding fusion helps explain viral tropism and cross-species transmission.
• Fusion is a model system for studying membrane merger in cell biology.
• The process is relevant to emerging viral pandemics and biodefense.
What Happens During fusion of virus membrane with host plasma membrane?
Viral Attachment and Receptor Binding
In simple terms: The virus first sticks to the cell surface by binding to specific receptors.
The fusion process begins with the attachment of the virus to host cell receptors, which can be proteins, carbohydrates, or lipids. For example, influenza virus hemagglutinin binds to sialic acid residues, while SARS-CoV-2 spike protein binds to ACE2. This binding is often a trigger for conformational changes in the viral fusion protein that prime it for membrane fusion. Receptor binding can also determine host range and tissue tropism.
Activation of the Fusion Protein
In simple terms: The viral fusion protein changes shape after being triggered by factors like low pH or cleavage by enzymes.
Fusion proteins require activation to expose their fusion peptide or internal fusion loop. Activation can occur through proteolytic cleavage by host proteases (e.g., TMPRSS2 for SARS-CoV-2) or by exposure to low pH in endosomes (e.g., influenza virus). For alphaherpesviruses, binding to a receptor triggers the fusion machinery composed of gB, gD, and gH/gL. These conformational changes insert the fusion peptide into the target membrane, anchoring the virus to the host membrane.
Hemifusion Intermediate
In simple terms: The outer layers of the viral and cell membranes merge, but the inner layers remain separate.
After insertion of the fusion peptide, the viral and host membranes are pulled together, leading to the formation of a hemifusion stalk where the outer leaflets of the lipid bilayers merge while the inner leaflets remain distinct. This hemifusion intermediate is a key step that can be stabilized by host factors such as IFITM3, which restricts fusion by altering lipid ordering. Hemifusion is reversible and represents a point of regulation.
Formation of the Fusion Pore
In simple terms: A hole opens up between the viral and cell membranes, allowing the viral contents to enter.
The hemifusion intermediate resolves into a fusion pore, a small opening that connects the viral interior with the host cytoplasm. This pore expands to allow the release of the viral genome and other contents into the cytoplasm. For viruses that fuse at the plasma membrane, this step occurs directly at the cell surface, as visualized by single-virus tracking for SARS-CoV-2. The formation of the fusion pore is driven by the free energy released from the conformational changes of the fusion protein.
Release of Viral Contents
In simple terms: The viral genetic material and proteins are released into the cell to start infection.
Once the fusion pore is fully open, the viral nucleocapsid or genome is released into the cytoplasm, where replication begins. For influenza virus, the release of ribonucleoproteins into the cytoplasm is essential for transcription and replication. This step completes the entry process and marks the transition to viral replication.
Key Genes Involved in GO:0019064 fusion of virus membrane with host plasma membrane
The following genes and proteins are central to the fusion of virus membrane with host plasma membrane, either as viral fusion machinery or host factors that regulate the process.
| Gene | Major Role | Research Relevance |
|---|---|---|
| HA (influenza hemagglutinin) | Viral fusion protein that mediates membrane fusion upon low pH activation | Model for class I fusion proteins; target of neutralizing antibodies |
| S (SARS-CoV-2 spike) | Binds ACE2 and mediates fusion at plasma membrane or endosome | Key target for vaccines and antivirals; studied by single-virus tracking |
| gB (herpes simplex virus) | Conserved fusion protein that executes membrane merger | Essential for alphaherpesvirus entry; target of neutralizing antibodies |
| gD (herpes simplex virus) | Receptor-binding protein that triggers fusion | Determines cell tropism and triggers gB/gH/gL |
| gH/gL (herpes simplex virus) | Regulatory complex that activates gB | Component of the fusion machinery; antibody target |
| IFITM3 | Host restriction factor that blocks fusion by altering lipid order | Inhibits influenza and other enveloped viruses; stabilizes hemifusion |
| ACE2 | Host receptor for SARS-CoV-2 spike | Determines susceptibility and tissue tropism |
| TMPRSS2 | Host protease that cleaves SARS-CoV-2 spike to activate fusion | Enhances plasma membrane fusion; drug target |
| Cathepsin L | Endosomal protease that activates spike for fusion | Alternative activation pathway in endosomes |
| Sialic acid receptors | Host glycans that bind influenza HA | Attachment factors for influenza virus |
| Cholesterol | Lipid component that modulates membrane fluidity and fusion | Influences hemifusion and pore formation |
| Phosphatidylserine | Lipid exposed on viral envelope that can enhance fusion | Potential target for broad-spectrum antivirals |
| TMPRSS2 | Protease that cleaves and activates viral fusion proteins | Host factor for SARS-CoV-2 and influenza |
| Furin | Protease that cleaves some viral fusion proteins | Activates spike during virus production |
| IFITM1 | Host restriction factor similar to IFITM3 | Blocks fusion of various enveloped viruses |
| IFITM2 | Host restriction factor | Restricts viral entry |
| CLEC4M/DC-SIGN | Attachment factor for some viruses | Enhances infection in dendritic cells |
| Nectin-1 | Herpesvirus entry receptor | Mediates gD binding and fusion |
How Is fusion of virus membrane with host plasma membrane Regulated?
The fusion of virus membrane with host plasma membrane is regulated at multiple levels. Host restriction factors such as IFITM3 can inhibit fusion by sorting lipids and stabilizing hemifusion intermediates, thereby preventing the formation of a fusion pore. Proteolytic activation of viral fusion proteins by host proteases like TMPRSS2 and cathepsins is a critical regulatory step that determines whether fusion occurs at the plasma membrane or in endosomes. Additionally, the lipid composition of the target membrane, including cholesterol and phosphatidylserine, can modulate fusion efficiency. Viral factors, such as the density of fusion proteins and their conformational stability, also influence the rate and extent of fusion. Finally, cellular signaling pathways that affect actin dynamics and membrane trafficking can impact the availability of receptors and proteases, indirectly regulating fusion.
fusion of virus membrane with host plasma membrane and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| HA (influenza) | Influenza virus infection | KO of HA in reverse genetics; point mutations to alter pH threshold |
| S (SARS-CoV-2) | COVID-19 | Knock-in of spike mutations; overexpression for pseudovirus entry assays |
| gB (HSV-1) | Herpes simplex encephalitis and cold sores | KO of gB in HSV-1; point mutations to map fusion loops |
| IFITM3 | Severe influenza and viral susceptibility | KO and overexpression in cell lines; knock-in of human SNP |
| ACE2 | SARS-CoV-2 susceptibility | KO in cell lines; humanized knock-in mouse models |
Influenza Virus Infection
Influenza virus relies on the fusion of its envelope with the host plasma membrane or endosomal membrane to release its genome. The hemagglutinin protein mediates this fusion upon low pH activation in endosomes. Monoclonal antibodies targeting specific epitopes on hemagglutinin can inhibit fusion and neutralize the virus, highlighting the importance of this process as a therapeutic target. IFITM3 restricts influenza virus entry by blocking fusion, and individuals with certain IFITM3 polymorphisms may be more susceptible to severe influenza.
COVID-19
SARS-CoV-2 entry involves binding of the spike protein to ACE2 and subsequent fusion at the plasma membrane or within endosomes. The fusion peptide of spike inserts into the host membrane, and proteolytic cleavage by TMPRSS2 or cathepsins is required for activation. Single-virus tracking has revealed that SARS-CoV-2 can fuse directly with the plasma membrane, a process that is a target for neutralizing antibodies and antiviral drugs. Understanding the fusion mechanism is critical for developing vaccines and therapeutics against COVID-19.
Herpes Simplex Virus Infections
Alphaherpesviruses such as herpes simplex virus 1 (HSV-1) enter cells by fusing their envelope with the plasma membrane, a process mediated by the conserved fusion protein gB and the regulatory complex gH/gL, triggered by gD binding to a receptor. This fusion event is essential for the establishment of latent and lytic infections. Mutations in gB or gH/gL can abolish fusion and viral entry, and antibodies against these proteins can neutralize the virus. The study of HSV fusion has provided insights into class III fusion proteins and their mechanisms.
Virus-Induced Cell-Cell Fusion
Some enveloped viruses, including herpesviruses and coronaviruses, can induce fusion between infected and neighboring cells, forming syncytia. This process is mediated by viral fusion proteins expressed on the cell surface and can contribute to tissue damage and immune evasion. Cell-cell fusion is a pathological hallmark of certain viral infections, such as respiratory syncytial virus and measles virus, and can be studied using reporter assays. Understanding the mechanisms of virus-mediated cell-cell fusion is important for developing therapies that limit viral spread.
From fusion of virus membrane with host plasma membrane-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X regulate viral fusion at the plasma membrane? | CRISPR KO of gene X in permissive cells followed by fusion assay |
| Does a specific point mutation in a viral fusion protein alter fusion efficiency? | Point mutation knock-in of the viral gene in reverse genetics system |
| Can a host factor be tagged to visualize its role in fusion? | Knock-in of fluorescent tag (e.g., GFP) at the endogenous locus |
| Does overexpression of a host factor enhance or inhibit fusion? | Overexpression of the gene of interest in target cells |
| Which host genes are essential for viral fusion? | Genome-wide CRISPR library screening with a fusion-dependent reporter virus |
| Does a SNP in IFITM3 affect fusion restriction? | Knock-in of the SNP in a cell line; fusion assay with influenza virus |
How to Study the fusion of virus membrane with host plasma membrane Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Single-virus tracking | Real-time fusion events and kinetics | Studying SARS-CoV-2 fusion at plasma membrane |
| Reporter virus fusion assay | Fusion pore formation and content mixing | High-throughput screening for fusion inhibitors |
| Cell-cell fusion assay | Syncytia formation | Studying viral fusion proteins and syncytia |
| Proteomics | Protein-protein interactions | Identifying host factors in fusion |
| Lipidomics | Membrane lipid composition | Assessing role of cholesterol in fusion |
| CRISPR KO screening | Host genes required for fusion | Discovering antiviral targets |
| CRISPR activation screening | Host genes that restrict fusion | Identifying restriction factors |
| Neutralization assay | Antibody inhibition of fusion | Evaluating vaccine responses |
Single-Virus Tracking
Single-virus tracking uses fluorescently labeled viruses to follow individual fusion events in real time, providing quantitative data on the kinetics and location of fusion. This method has been used to reveal that SARS-CoV-2 can fuse directly with the plasma membrane, and it can distinguish between fusion at the plasma membrane versus endosomes. It is particularly useful for studying the dynamics of hemifusion and pore formation.
Fusion Assays
Fusion assays often use reporter systems, such as beta-lactamase or luciferase, that are activated upon mixing of viral and cellular contents. These assays can be adapted for high-throughput screening to identify inhibitors or host factors. Cell-cell fusion assays can also be used to study viral fusion proteins expressed on the cell surface.
Proteomics and Lipidomics
Proteomic approaches can identify host proteins that interact with viral fusion proteins or that are recruited to fusion sites. Lipidomics can reveal changes in membrane lipid composition that affect fusion, such as the role of cholesterol and phosphatidylserine. These methods help elucidate the host machinery involved in fusion.
CRISPR Screening
Genome-wide CRISPR knockout or activation screens can identify host genes that are essential for or restrict viral fusion. For example, screens with influenza virus or SARS-CoV-2 have identified IFITM3 and other factors. These screens are powerful for discovering novel therapeutic targets.
How CRISPR Can Be Used to Study GO:0019064 fusion of virus membrane with host plasma membrane
Knockout
CRISPR knockout of host genes can determine whether they are required for viral fusion. For example, knockout of ACE2 abolishes SARS-CoV-2 entry, and knockout of IFITM3 increases influenza virus fusion. Knockout of viral genes in reverse genetics systems can also assess their necessity for fusion.
Point Mutation
Point mutations can be introduced into viral fusion proteins to map functional domains, such as the fusion peptide or hinge regions. For instance, mutations in the influenza hemagglutinin that alter the pH threshold for fusion can be generated to study activation. Similarly, point mutations in SARS-CoV-2 spike can affect fusion efficiency and antibody escape.
Knock-in
Knock-in of reporter tags or disease-associated SNPs can provide insights into fusion regulation. For example, knocking in a fluorescent tag into IFITM3 allows visualization of its localization during fusion. Knock-in of human ACE2 into mouse cells can create a model for SARS-CoV-2 fusion.
Overexpression
Overexpression of host or viral fusion proteins can enhance fusion and facilitate biochemical studies. Overexpression of SARS-CoV-2 spike in cells can induce cell-cell fusion, which can be used to test inhibitors. Overexpression of IFITM3 can protect cells from fusion-mediated entry.
How EDITGENE Supports fusion of virus membrane with host plasma membrane Research
Researchers studying fusion of virus membrane with host plasma membrane-related genes often need to determine whether a candidate gene is causally involved in the fusion process or is merely a bystander. This requires precise genetic manipulation, such as knockout, point mutation, knock-in, or overexpression, to establish causality. EDITGENE provides a comprehensive suite of CRISPR services to enable such studies in relevant cell models.
Contact EDITGENE today to design your custom CRISPR model for fusion of virus membrane with host plasma membrane research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| GAS6 Knockout HEK293 Cell Line | EDJ-KQ3061 | Human | 2621 | Details Get a Quote |
| NECTIN2 Knockout HEK293 Cell Line | EDJ-KQ5614 | Human | 5819 | Details Get a Quote |
| CTSL Knockout A-549 Cell Line | EDJ-KQ19864 | Human | 1514 | Details Get a Quote |
| CTSL Knockout HCT 116 Cell Line | EDJ-KQ19865 | Human | 1514 | Details Get a Quote |
| CTSL Knockout HeLa Cell Line | EDJ-KQ19866 | Human | 1514 | Details Get a Quote |
| GAS6 Knockout A-549 Cell Line | EDJ-KQ25695 | Human | 2621 | Details Get a Quote |
| GAS6 Knockout HCT 116 Cell Line | EDJ-KQ25696 | Human | 2621 | Details Get a Quote |
| GAS6 Knockout HeLa Cell Line | EDJ-KQ25697 | Human | 2621 | Details Get a Quote |
| NECTIN2 Knockout A-549 Cell Line | EDJ-KQ28910 | Human | 5819 | Details Get a Quote |
| NECTIN2 Knockout HCT 116 Cell Line | EDJ-KQ28911 | Human | 5819 | Details Get a Quote |
| NECTIN2 Knockout HeLa Cell Line | EDJ-KQ28912 | Human | 5819 | Details Get a Quote |
| CTSL Knockout HEK293 Cell Line | EDC90403 | Human | 1514 | Details Get a Quote |
Frequently Asked Questions About fusion of virus membrane with host plasma membrane
What is GO:0019064?
GO:0019064 is a Gene Ontology term for the biological process 'fusion of virus membrane with host plasma membrane', which describes the merger of the viral envelope with the host cell plasma membrane during viral entry, releasing the virion contents into the cytoplasm.
What genes are involved in fusion of virus membrane with host plasma membrane?
Key genes include viral fusion proteins such as influenza hemagglutinin (HA), SARS-CoV-2 spike (S), and herpes simplex virus glycoproteins (gB, gD, gH/gL), as well as host factors like ACE2, TMPRSS2, and IFITM3.
How does the viral membrane fuse with the host plasma membrane?
The process involves receptor binding, activation of the viral fusion protein, insertion of the fusion peptide into the host membrane, formation of a hemifusion intermediate, and opening of a fusion pore that releases the viral genome.
What is the role of IFITM3 in viral fusion?
IFITM3 is a host restriction factor that blocks influenza virus entry by sorting lipids and stabilizing hemifusion, thereby preventing the formation of a fusion pore.
Which viruses use fusion with the plasma membrane for entry?
Many enveloped viruses can fuse at the plasma membrane, including SARS-CoV-2, herpes simplex virus, and some retroviruses, although influenza virus typically fuses in endosomes.
How can I study fusion of virus membrane with host plasma membrane?
Common methods include single-virus tracking, reporter virus fusion assays, cell-cell fusion assays, proteomics, lipidomics, and CRISPR screening.
What is the difference between fusion at the plasma membrane and endosomal fusion?
Plasma membrane fusion occurs at the cell surface and is often triggered by receptor binding or proteases like TMPRSS2, while endosomal fusion requires low pH and proteases like cathepsins after endocytosis.
Can CRISPR be used to study viral fusion?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression can be used to manipulate host or viral genes and assess their impact on fusion.
What diseases are associated with defects in viral fusion?
Viral fusion is essential for infections such as influenza, COVID-19, and herpes simplex encephalitis; host factors that regulate fusion can influence susceptibility and disease severity.
What are the therapeutic implications of understanding viral fusion?
Understanding fusion mechanisms aids in the development of fusion inhibitors, neutralizing antibodies, and vaccines that target viral entry.
Conclusion
GO:0019064, fusion of virus membrane with host plasma membrane, is a fundamental process in the entry of enveloped viruses and a key target for antiviral strategies. The interplay between viral fusion proteins and host factors determines the efficiency and location of fusion, with significant implications for viral pathogenesis and host range. Advanced techniques such as single-virus tracking and CRISPR screening continue to unravel the molecular details of this process, offering new opportunities for therapeutic intervention. EDITGENE provides a comprehensive toolkit of CRISPR cell models and screening services to support research on viral fusion and to accelerate the discovery of novel antiviral targets.
References
- 1. Leroy H et al.. 2020. Virus-Mediated Cell-Cell Fusion.. Int J Mol Sci 21(24) PMID: 33348900
- 2. Klein S et al.. 2023. IFITM3 blocks influenza virus entry by sorting lipids and stabilizing hemifusion.. Cell Host Microbe 31(4):616-633.e20 PMID: 37003257
- 3. Liu HY et al.. 2024. Quantitative single-virus tracking for revealing the dynamics of SARS-CoV-2 fusion with plasma membrane.. Sci Bull (Beijing) 69(4):502-511 PMID: 37993331
- 4. Cairns TM et al.. 2021. Entry of Alphaherpesviruses.. Curr Issues Mol Biol 41:63-124 PMID: 32764159
- 5. Wędrowska E et al.. 2020. Coronaviruses fusion with the membrane and entry to the host cell.. Ann Agric Environ Med 27(2):175-183 PMID: 32588590
- 6. Mas V et al.. 2024. Entry of Enveloped Viruses into Host Cells: Membrane Fusion.. Subcell Biochem 105:567-592 PMID: 39738958
- 7. Imai M et al.. 1998. Fusion of influenza virus with the endosomal membrane is inhibited by monoclonal antibodies to defined epitopes on the hemagglutinin.. Virus Res 53(2):129-39 PMID: 9620205
- 8. Schaefer SL et al.. 2021. Binding of SARS-CoV-2 Fusion Peptide to Host Endosome and Plasma Membrane.. J Phys Chem B 125(28):7732-7741 PMID: 34255499
