GO:0046598 positive regulation of viral entry into host cell: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0046598 describes any process that activates or increases the frequency, rate or extent of viral entry into a host cell, including viral penetration and fusion steps.
• Positive regulation of entry is often mediated by host factors that remodel membranes, alter receptor availability, or promote syncytium formation, as shown for SARS-CoV-2 and HIV-1.
• Host glycosylation and chemokine receptor usage can select for CCR5- versus CXCR4-tropic HIV-1, directly influencing entry efficiency.
• CDC42 supports HBV entry by promoting NTCP translocation to the plasma membrane and macropinocytosis, illustrating a GTPase-dependent positive regulatory mechanism.
• Lysosomal egress pathways for beta-coronaviruses can indirectly enhance subsequent entry events by releasing infectious virions.
• CRISPR knockout, knock-in, and overexpression models are essential to test whether candidate host genes causally increase viral entry.
Description
Positive regulation of viral entry into host cell (GO:0046598) is a biological process that encompasses any cellular activity that activates or increases the frequency, rate or extent of virus entry into a host cell. This term is distinct from the entry process itself because it specifically captures host or viral factors that enhance, rather than execute, the penetration step. Understanding this GO term is critical for virology researchers because entry is the first committed step of infection, and its positive regulators often represent therapeutic targets or determinants of host range. Mechanistically, positive regulation can occur through multiple routes. For example, host cell glycosylation can select for CCR5- versus CXCR4-tropic HIV-1, thereby increasing the efficiency of entry for specific viral variants. In the case of SARS-CoV-2, syncytia formation by infected cells can amplify viral spread and indirectly promote entry into neighboring cells. For HBV, the GTPase CDC42 supports entry by facilitating NTCP translocation to the plasma membrane and macropinocytosis. These examples illustrate that positive regulation is often context-dependent and involves dynamic host membrane trafficking. From a research perspective, GO:0046598 is a useful annotation for interpreting genome-wide CRISPR screens, transcriptomic shifts, and proteomic changes during infection. It helps distinguish genes that are required for entry from those that enhance entry efficiency. This article synthesizes authoritative QuickGO data and verified PubMed literature to provide a publication-ready overview of the term, its mechanisms, key genes, disease links, and experimental models.
positive regulation of viral entry into host cell At A Glance
| GO ID | GO:0046598 |
|---|---|
| GO term | positive regulation of viral entry into host cell |
| Ontology | biological_process |
| Synonym | positive regulation of viral penetration into host cell |
| Major function | Enhances the frequency, rate or extent of viral entry into a host cell |
| Related processes | Viral entry, membrane fusion, endocytosis, macropinocytosis, syncytium formation |
| Cellular context | Plasma membrane, endosomes, lysosomes, cell-cell junctions |
| Example viruses | SARS-CoV-2, HIV-1, HBV, beta-coronaviruses |
| Research relevance | Target identification, host-range determinants, antiviral development |
What Is GO:0046598?
In our own words, GO:0046598 refers to any host or viral process that boosts the introduction of viral material into a host cell. It does not describe the entry machinery itself, but rather the regulatory inputs that increase the likelihood, speed, or extent of viral penetration. This includes signaling events, receptor clustering, membrane remodeling, and extracellular factors that enhance fusion or endocytosis.
Why Is positive regulation of viral entry into host cell Important in Cell Biology?
Positive regulation of viral entry is a central determinant of infection efficiency and tropism. Because entry is the first step of the viral life cycle, even modest increases in entry rate can dramatically affect viral spread and disease outcome. Host factors that positively regulate entry are therefore attractive targets for antiviral intervention, and their genetic variation can explain differences in susceptibility. Moreover, understanding this process helps interpret CRISPR screens and functional genomics data, where candidate genes may act as enhancers rather than essential entry factors.
• Entry is the first committed step of infection; positive regulators can set the threshold for productive infection.
• Host glycosylation patterns can select for specific HIV-1 tropism, directly linking positive regulation to viral evolution.
• CDC42-mediated NTCP translocation enhances HBV entry, showing that host GTPases are key positive regulators.
• Syncytia formation by SARS-CoV-2-infected cells can amplify viral spread and promote entry into new cells.
• Lysosomal egress of beta-coronaviruses can increase the availability of infectious virions for subsequent entry.
• Positive regulators are candidate antiviral targets because inhibiting them may reduce entry without blocking essential host functions.
• CRISPR screens frequently identify positive regulators that are not essential for entry but enhance its efficiency.
• Understanding positive regulation helps explain cell-type specificity and host range of viruses.
• Disease severity in viral infections can correlate with enhanced entry efficiency.
• The term is used in functional annotation to distinguish enhancers from essential entry factors.
What Happens During positive regulation of viral entry into host cell?
Receptor availability and clustering
In simple terms: The virus needs its receptor to be present and accessible on the cell surface; positive regulation can increase receptor numbers or gather them together.
Positive regulation often begins with increasing the surface availability of viral receptors. For HBV, CDC42 supports entry by promoting translocation of the NTCP receptor to the plasma membrane, thereby enhancing the opportunity for virus binding and subsequent macropinocytosis. Similarly, host glycosylation can influence the conformation or accessibility of chemokine receptors, selecting for CCR5- versus CXCR4-tropic HIV-1 and thus positively regulating entry for specific variants.
Membrane remodeling and macropinocytosis
In simple terms: The cell membrane can be reshaped to engulf the virus more efficiently.
Membrane remodeling is a key positive regulatory mechanism. CDC42-dependent signaling promotes macropinocytosis, a process that can internalize HBV particles and increase entry efficiency. In beta-coronaviruses, lysosomal egress pathways can release virions that then re-enter neighboring cells, indirectly enhancing the overall rate of entry. These membrane dynamics are often triggered by viral attachment and host signaling.
Syncytium formation and cell-to-cell spread
In simple terms: Infected cells can fuse with neighboring cells, allowing the virus to spread without leaving the cell.
Syncytia formation by SARS-CoV-2-infected cells is a positive regulatory mechanism for viral entry because it allows direct cell-to-cell transmission, bypassing the need for extracellular virions. This process increases the effective rate of entry into new cells and can contribute to tissue damage. Similar mechanisms have been described for other enveloped viruses, where fusion between infected and uninfected cells amplifies spread.
Host glycosylation and tropism selection
In simple terms: Sugar modifications on host proteins can determine which virus variants can enter.
Host cell glycosylation can select for infection with CCR5- versus CXCR4-tropic HIV-1, meaning that the glycosylation state of the target cell positively regulates entry for specific viral strains. This selection influences viral tropism and disease progression. Glycosylation can affect receptor binding affinity, viral envelope stability, or immune recognition, all of which can enhance entry efficiency.
Endosomal and lysosomal trafficking
In simple terms: After being taken up, the virus must be trafficked to the right compartment to penetrate; positive regulation can speed this up.
For many viruses, entry requires trafficking through endosomes or lysosomes. Beta-coronaviruses use lysosomes for egress instead of the biosynthetic secretory pathway, and this can influence the availability of virions for subsequent entry events. Positive regulation of entry can therefore involve host factors that accelerate endosomal maturation or lysosomal fusion, thereby increasing the rate of viral penetration.
Key Genes Involved in GO:0046598 positive regulation of viral entry into host cell
The following genes and proteins have been experimentally linked to positive regulation of viral entry into host cells, based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CDC42 | Promotes NTCP translocation and macropinocytosis for HBV entry | GTPase-dependent positive regulator; target for entry inhibition |
| NTCP | HBV receptor; surface availability regulated by CDC42 | Key entry receptor; model for trafficking studies |
| CCR5 | HIV-1 co-receptor; glycosylation influences tropism | Determinant of CCR5-tropic HIV-1 entry |
| CXCR4 | HIV-1 co-receptor; alternative tropism | Determinant of CXCR4-tropic HIV-1 entry |
| ACE2 | SARS-CoV-2 receptor | Essential for entry; syncytia formation enhances spread |
| TMPRSS2 | Protease that primes SARS-CoV-2 spike | Facilitates membrane fusion and entry |
| PDGFA-associated protein 1 | Regulates ER stress and hepatovirus translation | Indirectly supports entry by promoting viral protein synthesis |
| HLA class II | Converted from CD4+ T cells during HIV-1 infection | Alters cell identity and potentially entry susceptibility |
| CD4 | Primary HIV-1 receptor | Required for entry; downregulated or converted in infection |
| LAMP1 | Lysosomal marker involved in beta-coronavirus egress | Links lysosomal trafficking to entry efficiency |
| Rab7 | Late endosome/lysosome trafficking | Potential regulator of entry via endosomal routing |
| Cathepsin L | Protease that can prime viral glycoproteins | May enhance entry in endosomes |
| IFITM proteins | Restrict viral entry; their absence can enhance entry | Negative regulators whose loss increases entry |
| Sialic acid | Glycan component affecting receptor binding | Host glycosylation selects viral tropism |
| Integrin alphaV beta3 | Potential co-receptor for entry | Candidate positive regulator in some viruses |
| EGFR | Signaling receptor that can promote endocytosis | May enhance entry via macropinocytosis |
| Rho GTPases | Cytoskeletal remodeling | Family of positive regulators of entry |
How Is positive regulation of viral entry into host cell Regulated?
Positive regulation of viral entry is itself regulated by host signaling pathways. For example, CDC42 activity is controlled by guanine nucleotide exchange factors and GTPase-activating proteins, and its activation state determines the extent of NTCP translocation and macropinocytosis for HBV. Host glycosylation pathways regulate the selection of CCR5- versus CXCR4-tropic HIV-1, meaning that enzymes controlling glycan addition can act as upstream regulators of entry efficiency. In addition, endoplasmic reticulum stress responses can modulate the translation of viral proteins that are needed for entry, as shown for hepatovirus translation requiring PDGFA-associated protein 1. These regulatory layers provide multiple nodes for therapeutic intervention.
positive regulation of viral entry into host cell and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| CCR5 | HIV-1 tropism and progression | Knockout in CD4+ T cells; entry assays |
| CXCR4 | HIV-1 tropism and progression | Knockout or overexpression in T cell lines |
| CDC42 | HBV entry and liver disease | Knockout hepatocytes; NTCP translocation assays |
| ACE2 | SARS-CoV-2 entry and syncytia | Knockout or overexpression in lung epithelial cells |
| TMPRSS2 | SARS-CoV-2 fusion and entry | Point mutation or knockout in airway cells |
HIV-1 tropism and disease progression
Host cell glycosylation selects for infection with CCR5- versus CXCR4-tropic HIV-1, which is a major determinant of viral tropism and disease progression. Positive regulation of entry by glycosylation pathways can influence which cell types are infected and how quickly the virus spreads. Additionally, HIV-1 infection can convert CD4+ T cells to HLA class II-restricted CD8+ T cells, altering the target cell pool and potentially affecting entry dynamics.
SARS-CoV-2 syncytia and severe COVID-19
Syncytia formation by SARS-CoV-2-infected cells is a positive regulatory mechanism that enhances viral spread and is associated with severe COVID-19 pathology. By promoting cell-to-cell fusion, the virus can enter neighboring cells without exposure to extracellular neutralizing antibodies, contributing to tissue damage and inflammation. This mechanism highlights how positive regulation of entry can directly impact disease severity.
HBV entry and liver disease
CDC42 supports HBV entry by promoting NTCP translocation to the plasma membrane and macropinocytosis, linking a host GTPase to liver infection. Enhanced entry efficiency can increase viral load and contribute to chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Targeting positive regulators like CDC42 may offer new therapeutic strategies for HBV.
From positive regulation of viral entry into host cell-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is CDC42 required for HBV entry? | CDC42 knockout hepatocytes with NTCP translocation assay |
| Does glycosylation determine HIV-1 tropism? | Knockout of glycosyltransferases in CD4+ T cells |
| Does ACE2 overexpression enhance SARS-CoV-2 entry? | ACE2 overexpression in lung epithelial cells |
| Does TMPRSS2 point mutation block spike priming? | TMPRSS2 point-mutation knock-in cells |
| Does HLA class II conversion affect entry? | Knock-in of HLA class II in CD4+ T cells |
| Does PDGFA-associated protein 1 regulate hepatovirus translation? | Knockout of PDGFA-associated protein 1 in hepatocytes |
How to Study the positive regulation of viral entry into host cell Process
| Method | What It Measures | Typical Application |
|---|---|---|
| CRISPR knockout screen | Loss-of-function effects on viral entry | Identify host positive regulators |
| Pseudotyped virus entry assay | Entry efficiency of specific viral glycoproteins | Test candidate genes |
| Live-cell imaging | Real-time entry and syncytia formation | Visualize positive regulation |
| Glycosylation profiling | Host glycan structures | Link glycosylation to tropism |
| Proteomics | Protein abundance and interactions | Discover entry-associated factors |
| RNA-seq | Transcriptional changes during infection | Identify upregulated entry enhancers |
| Macropinocytosis assay | Uptake of fluid-phase markers | Measure CDC42-dependent entry |
| NTCP translocation assay | Surface localization of HBV receptor | Study CDC42 regulation |
CRISPR knockout screens for entry regulators
Genome-wide CRISPR knockout screens can identify host genes whose loss reduces or enhances viral entry. For example, screens have implicated CDC42 in HBV entry and ACE2/TMPRSS2 in SARS-CoV-2 entry. These screens are powerful for discovering positive regulators because they can distinguish genes that are essential for entry from those that modulate its efficiency.
Glycosylation profiling and tropism assays
Mass spectrometry and lectin-based assays can profile host cell glycosylation, which selects for CCR5- versus CXCR4-tropic HIV-1. Combining glycosylation profiling with entry assays using pseudotyped viruses allows researchers to link specific glycan structures to entry efficiency.
Live-cell imaging of entry and syncytia
Live-cell imaging with fluorescently labeled viruses or viral proteins can visualize entry events, membrane fusion, and syncytia formation in real time. This method is particularly useful for studying positive regulation by cell-to-cell spread and for quantifying the rate of entry.
Proteomics and interactomics
Proteomic approaches can identify host proteins that associate with viral entry factors or that change abundance during infection. For example, PDGFA-associated protein 1 was identified as an eIF4E-binding protein regulating ER stress responses required for hepatovirus translation. Such studies can reveal novel positive regulators of entry.
How CRISPR Can Be Used to Study GO:0046598 positive regulation of viral entry into host cell
Knockout
CRISPR knockout of candidate positive regulators such as CDC42 or ACE2 can test whether they are required for efficient viral entry. Knockout cells are compared to wild-type controls in entry assays using pseudotyped or live viruses. This approach is ideal for validating hits from genome-wide screens.
Point Mutation
Point mutations can be introduced into host genes to dissect specific domains or residues that mediate positive regulation. For example, mutating the GTP-binding domain of CDC42 can determine whether its GTPase activity is required for HBV entry. Similarly, point mutations in TMPRSS2 can test its protease activity in SARS-CoV-2 entry.
Knock-in
Knock-in of tagged or variant alleles allows precise tracking of host proteins during entry. For instance, knocking in a fluorescent tag on NTCP can monitor its translocation to the plasma membrane in response to CDC42 signaling. Knock-in of HLA class II in CD4+ T cells can model the conversion observed during HIV-1 infection.
Overexpression
Overexpression of candidate positive regulators can test whether increasing their levels enhances viral entry. Overexpressing ACE2 or TMPRSS2 in cell lines can increase SARS-CoV-2 entry efficiency. Overexpression of glycosyltransferases can shift HIV-1 tropism by altering receptor glycosylation.
How EDITGENE Supports positive regulation of viral entry into host cell Research
Researchers studying positive regulation of viral entry into host cell-related genes often need to determine whether a candidate gene is causally involved in enhancing entry or is merely correlated with infection. This requires precise genetic models that can isolate the contribution of a single host factor. EDITGENE provides a comprehensive suite of CRISPR services to generate such models, from knockout to knock-in and overexpression, enabling rigorous functional validation.
Contact EDITGENE today to design your custom CRISPR model for positive regulation of viral entry into host cell research.
Frequently Asked Questions About positive regulation of viral entry into host cell
What is GO:0046598 positive regulation of viral entry into host cell?
It is a Gene Ontology biological process term describing any process that activates or increases the frequency, rate or extent of viral entry into a host cell.
What genes are involved in positive regulation of viral entry?
Genes such as CDC42, ACE2, TMPRSS2, CCR5, and CXCR4 have been implicated in enhancing viral entry.
How does CDC42 regulate HBV entry?
CDC42 supports HBV entry by promoting NTCP translocation to the plasma membrane and macropinocytosis.
Does glycosylation affect HIV-1 entry?
Yes, host cell glycosylation selects for infection with CCR5- versus CXCR4-tropic HIV-1, thereby influencing entry efficiency.
What is the role of syncytia in SARS-CoV-2 entry?
Syncytia formation by SARS-CoV-2-infected cells enhances viral spread and entry into neighboring cells.
How can I study positive regulation of viral entry using CRISPR?
CRISPR knockout, knock-in, point mutation, and overexpression models can test whether candidate genes causally enhance entry.
Which viruses use lysosomal egress that affects entry?
Beta-coronaviruses use lysosomes for egress instead of the biosynthetic secretory pathway, which can influence subsequent entry events.
What methods identify positive regulators of viral entry?
Genome-wide CRISPR screens, pseudotyped virus entry assays, live-cell imaging, and proteomics are commonly used.
Is positive regulation of viral entry a therapeutic target?
Yes, host factors that enhance entry are candidate targets for antiviral intervention, as inhibiting them may reduce infection.
What cell models are suitable for studying GO:0046598?
Knockout, knock-in, point mutation, and overexpression cell lines in relevant cell types such as hepatocytes, T cells, and lung epithelial cells are suitable.
Conclusion
GO:0046598 positive regulation of viral entry into host cell captures a critical layer of host-virus interaction that determines infection efficiency and tropism. Through mechanisms such as receptor trafficking, glycosylation, macropinocytosis, and syncytia formation, host factors can enhance viral entry and influence disease outcomes. Understanding these processes provides opportunities for therapeutic intervention and for interpreting functional genomics data. Researchers can leverage CRISPR-based models and screening approaches to validate candidate positive regulators and dissect their mechanisms. EDITGENE offers end-to-end services to support such studies, from knockout and knock-in cell lines to library screening and bioinformatics.
References
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- 3. Itell HL et al.. 2024. Host cell glycosylation selects for infection with CCR5- versus CXCR4-tropic HIV-1.. Nat Microbiol 9(11):2985-2996 PMID: 39363105
- 4. Cai J et al.. 2026. HIV-1 infection converts CD4(+) T cells to HLA class II-restricted CD8(+) T cells.. Sci Transl Med 18(852):eaec4912 PMID: 42234775
- 5. Shirasaki T et al.. 2024. Hepatovirus translation requires PDGFA-associated protein 1, an eIF4E-binding protein regulating endoplasmic reticulum stress responses.. Sci Adv 10(47):eadq6342 PMID: 39565848
- 6. Cui S et al.. 2025. CDC42 supports HBV entry by NTCP translocation to the plasma membrane and macropinocytosis.. EMBO Rep 26(21):5239-5269 PMID: 40954218
- 7. Council OD et al.. 2018. Evolution of Host Target Cell Specificity During HIV-1 Infection.. Curr HIV Res 16(1):13-20 PMID: 29268687
- 8. Buchrieser J et al.. 2020. Syncytia formation by SARS-CoV-2-infected cells.. EMBO J 39(23):e106267 PMID: 33051876
