GO:0031623 receptor internalization: Endocytic Trafficking Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0031623 receptor internalization is a receptor-mediated endocytosis process that moves cell surface receptors from the plasma membrane into the cell after ligand-induced monoubiquitination.
• Internalized receptors are sorted into endocytic vesicles and then either degraded in lysosomes/vacuoles or recycled back to the plasma membrane.
• The process is best characterized for G protein-coupled receptors (GPCRs), including chemokine receptors, angiotensin II receptors, delta-opioid receptors, endothelin type-A receptors, GPR15 and mGluR2.
• Posttranslational modifications such as ubiquitination and phosphorylation are central to receptor internalization and subsequent intracellular trafficking.
• Receptor internalization influences physiological signaling, viral entry and disease processes such as neuropsychiatric disorders, cardiovascular disease and viral infection.
• CRISPR knockout, point-mutation, knock-in and overexpression cell models enable causal dissection of receptor internalization genes and their trafficking routes.
Description
Receptor internalization (GO:0031623) is a biological process in which cell surface receptors are moved from the plasma membrane to the inside of the cell through a receptor-mediated endocytosis mechanism. The process begins when cell surface receptors are monoubiquitinated following ligand-induced activation, and the receptors are subsequently taken up into endocytic vesicles from where they are either targeted to the lysosome or vacuole for degradation or recycled back to the plasma membrane. This definition places receptor internalization at the intersection of signal transduction, membrane trafficking and protein degradation. Researchers study this term because it controls the duration and intensity of receptor signaling, determines receptor resensitization versus downregulation, and provides a route for pathogens and therapeutic cargo to enter cells. The process is particularly well documented for G protein-coupled receptors (GPCRs), where ligand binding triggers conformational changes, receptor phosphorylation and ubiquitination, followed by recruitment of endocytic machinery. Chemokine receptors, angiotensin II receptors, delta-opioid receptors, endothelin type-A receptors, GPR15 and mGluR2 are among the receptors whose internalization has been experimentally dissected. Because receptor internalization is a convergence point for signaling, trafficking and degradation, it is a frequent target of genetic and pharmacological studies in cell biology, neuroscience, immunology and virology.
receptor internalization At A Glance
| GO ID | GO:0031623 |
|---|---|
| GO term | receptor internalization |
| Ontology | biological_process |
| Synonym | none |
| Major function | Receptor-mediated endocytosis that moves receptors from the plasma membrane to the inside of the cell |
| Trigger | Monoubiquitination of cell surface receptors following ligand-induced activation |
| Vesicle fate | Endocytic vesicles deliver receptors to lysosome or vacuole for degradation, or recycle them back to the plasma membrane |
| Representative receptors | Chemokine receptors, angiotensin II receptor, delta-opioid receptor, endothelin type-A receptor, GPR15, mGluR2 |
| Related modifications | Posttranslational modifications including ubiquitination and phosphorylation regulate GPCR internalization |
What Is GO:0031623?
In your own words, GO:0031623 receptor internalization is the ligand-triggered, receptor-mediated endocytic movement of receptors from the plasma membrane to the cell interior. The process is initiated when cell surface receptors become monoubiquitinated after ligand-induced activation, and the receptors are then packaged into endocytic vesicles. From these vesicles, receptors are sorted either to lysosomes or vacuoles for degradation or recycled back to the plasma membrane.
Why Is receptor internalization Important in Cell Biology?
Receptor internalization is important because it determines how long a receptor remains at the cell surface and therefore how long a cell can respond to a ligand. By removing receptors from the plasma membrane and routing them to degradation or recycling, internalization controls signal termination, receptor resensitization and cellular adaptation. The process also contributes to physiology and disease: chemokine receptor trafficking shapes immune cell migration, delta-opioid receptor internalization is linked to opioid responses, endothelin type-A receptor internalization is relevant to cardiovascular biology, and mGluR2-associated internalization is exploited by rabies virus and SARS-CoV-2. Consequently, receptor internalization is a key process for understanding drug responses, viral entry and the molecular basis of multiple disorders.
• Controls the strength and duration of receptor signaling by removing activated receptors from the cell surface.
• Determines whether receptors are degraded in lysosomes/vacuoles or recycled back to the plasma membrane.
• Requires ligand-induced monoubiquitination of cell surface receptors as an initiating event.
• Is regulated by posttranslational modifications such as ubiquitination and phosphorylation of GPCRs.
• Shapes chemokine receptor function and immune cell trafficking.
• Modulates opioid receptor responses and neuropsychiatric biology.
• Contributes to cardiovascular signaling through angiotensin II and endothelin type-A receptors.
• Provides an entry route for pathogens such as rabies virus and SARS-CoV-2 via mGluR2 and transferrin receptor protein 1.
• Influences particle uptake efficiency through receptor properties during receptor-mediated endocytosis.
• Is a tractable target for CRISPR-based functional genomics of endocytic and trafficking genes.
What Happens During receptor internalization?
Ligand-induced activation and monoubiquitination
In simple terms: A ligand binds the receptor, and the receptor gets tagged with a small protein called ubiquitin.
The process begins when cell surface receptors are monoubiquitinated following ligand-induced activation. For GPCRs, ligand binding promotes conformational changes and posttranslational modifications, including ubiquitination and phosphorylation, that prepare the receptor for internalization. Chemokine receptors similarly undergo ligand-triggered internalization and intracellular trafficking. This step is the molecular switch that commits an activated receptor to the endocytic pathway.
Recruitment of endocytic machinery and vesicle uptake
In simple terms: The tagged receptor is pulled into the cell inside a small bubble called an endocytic vesicle.
After monoubiquitination, receptors are taken up into endocytic vesicles from the plasma membrane. Endocytic proteins mediate this uptake for specific receptors; for example, endocytic proteins mediating GPR15 receptor internalization provide insight into the underlying mechanisms. Receptor properties, such as density and affinity, influence the efficiency of particle internalization through receptor-mediated endocytosis. The result is movement of receptors from the plasma membrane to the inside of the cell.
Intracellular sorting: degradation versus recycling
In simple terms: Once inside, the receptor is sorted either to be destroyed or sent back to the cell surface.
Receptors taken up into endocytic vesicles are either targeted to the lysosome or vacuole for degradation or recycled back to the plasma membrane. This sorting decision determines whether the cell downregulates the receptor or restores it for further signaling. Chemokine receptor internalization and intracellular trafficking illustrate how sorting routes shape receptor fate. Angiotensin II receptor internalization studies similarly describe molecular mechanisms that govern receptor trafficking.
Receptor-specific mechanisms: GPCRs and other receptors
In simple terms: Different receptors use similar but not identical internalization routes.
GPCR internalization is regulated by posttranslational modifications, including ubiquitination and phosphorylation. Delta-opioid receptor internalization has been characterized in terms of mechanism and consequences. Type-A endothelin receptor internalization has been studied as a cardiovascular-relevant example. Transferrin receptor protein 1 cooperates with mGluR2 to mediate internalization of rabies virus and SARS-CoV-2, linking receptor internalization to viral entry.
Consequences for signaling and cell physiology
In simple terms: Internalization changes how the cell responds to signals over time.
By removing receptors from the plasma membrane, internalization terminates or attenuates ligand-induced signaling and can lead to receptor degradation or recycling. The consequences of delta-opioid receptor internalization have been reviewed in the context of receptor function. Chemokine receptor internalization and intracellular trafficking affect chemokine gradients and cell migration. Thus, receptor internalization is a central determinant of cellular responsiveness and adaptation.
Key Genes Involved in GO:0031623 receptor internalization
The following genes and proteins are experimentally implicated in receptor internalization, endocytic trafficking and related receptor-mediated endocytosis pathways.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CXCR4 | Chemokine receptor that undergoes internalization and intracellular trafficking | Model for GPCR internalization and immune cell migration |
| CCR5 | Chemokine receptor subject to internalization and trafficking | Studied in chemokine signaling and viral entry contexts |
| AGTR1 | Angiotensin II receptor that internalizes after ligand activation | Cardiovascular receptor internalization model |
| OPRD1 | Delta-opioid receptor with characterized internalization mechanism | Neuropsychiatric and opioid response studies |
| EDNRA | Type-A endothelin receptor that undergoes internalization | Cardiovascular signaling research |
| GPR15 | Receptor whose internalization is mediated by endocytic proteins | Mechanistic dissection of endocytic protein requirements |
| GRM2 | mGluR2 cooperates with transferrin receptor protein 1 in viral internalization | Viral entry and receptor trafficking studies |
| TFRC | Transferrin receptor protein 1 cooperates with mGluR2 for rabies virus and SARS-CoV-2 internalization | Host factor for viral internalization |
| UBB | Ubiquitin precursor contributing to monoubiquitination of receptors | Ubiquitination-dependent internalization studies |
| UBC | Ubiquitin precursor contributing to receptor monoubiquitination | Posttranslational modification analysis |
| GRK2 | G protein-coupled receptor kinase involved in GPCR phosphorylation preceding internalization | GPCR regulation studies |
| ARRB1 | Beta-arrestin 1 involved in GPCR internalization and trafficking | GPCR endocytosis research |
| ARRB2 | Beta-arrestin 2 involved in GPCR internalization and trafficking | GPCR endocytosis research |
| CLTC | Clathrin heavy chain component of endocytic vesicles | Endocytic uptake assays |
| AP2M1 | AP-2 adaptor complex subunit in receptor-mediated endocytosis | Endocytic machinery studies |
| RAB5A | Early endosome GTPase controlling receptor sorting | Intracellular trafficking analysis |
| RAB7A | Late endosome GTPase directing receptors to lysosomal degradation | Degradation versus recycling studies |
| VPS35 | Retromer component involved in receptor recycling | Recycling pathway research |
How Is receptor internalization Regulated?
Receptor internalization is regulated by posttranslational modifications, especially ubiquitination and phosphorylation of GPCRs, which control the timing and extent of receptor removal from the plasma membrane. Ligand-induced activation is the trigger for monoubiquitination of cell surface receptors, and this modification initiates the internalization process. Receptor properties such as density and affinity influence the efficiency of internalization through receptor-mediated endocytosis. Endocytic proteins determine receptor-specific uptake, as shown for GPR15 receptor internalization. After internalization, sorting decisions route receptors to lysosomes or vacuoles for degradation or back to the plasma membrane for recycling, providing an additional layer of regulation.
receptor internalization and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| OPRD1 | Delta-opioid receptor internalization and neuropsychiatric responses | Knockout and point-mutation cell models for internalization assays |
| AGTR1 | Angiotensin II receptor internalization in cardiovascular signaling | Overexpression and knockout models for trafficking studies |
| EDNRA | Type-A endothelin receptor internalization in cardiovascular biology | Knock-in reporter models for receptor localization |
| GRM2/TFRC | Rabies virus and SARS-CoV-2 internalization via mGluR2 and transferrin receptor protein 1 | Knockout cells for viral entry and internalization assays |
| CXCR4/CCR5 | Chemokine receptor internalization and intracellular trafficking | Tagged knock-in and knockout models for trafficking analysis |
Receptor internalization in neuropsychiatric and opioid-related disorders
Delta-opioid receptor internalization has been characterized in terms of mechanism and consequences, linking this process to opioid receptor function and neuropsychiatric biology. Because internalization controls receptor availability at the cell surface, altered internalization could influence responses to opioid ligands. Research on delta-opioid receptor internalization therefore provides a framework for understanding receptor trafficking in the nervous system.
Receptor internalization in cardiovascular disease
Angiotensin II receptor internalization is studied as a molecular mechanism relevant to cardiovascular signaling. Type-A endothelin receptor internalization has also been investigated in cardiovascular pharmacology. These examples show that receptor internalization is part of the regulatory logic of cardiovascular receptor systems.
Receptor internalization and viral entry
Transferrin receptor protein 1 cooperates with mGluR2 to mediate the internalization of rabies virus and SARS-CoV-2, demonstrating that receptor internalization pathways can be exploited by pathogens. This links GO:0031623 to host-pathogen interactions and suggests that endocytic trafficking components are relevant to viral entry research. Chemokine receptor internalization and intracellular trafficking are also relevant to immune and viral contexts.
Receptor internalization in immune cell migration and chemokine biology
Chemokine receptor internalization and intracellular trafficking are central to chemokine receptor function and immune cell behavior. Because chemokine receptors must be removed from the surface and either degraded or recycled to maintain responsiveness, defects in internalization can alter cell migration and positioning. This makes receptor internalization a process of interest in immunology and inflammation research.
From receptor internalization-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is a candidate gene required for receptor internalization? | CRISPR knockout cell line followed by internalization assay |
| Does a specific phosphorylation or ubiquitination site control internalization? | Point-mutation knock-in of the receptor or modifying enzyme |
| Where does the receptor traffic after internalization? | Tagged knock-in with fluorescent or affinity tag |
| Does overexpression of an endocytic protein enhance or inhibit internalization? | Overexpression cell model |
| Which endocytic proteins mediate receptor-specific uptake? | Knockout or knockdown of endocytic genes with receptor internalization readout |
| How do receptor properties affect particle internalization? | Engineered receptor expression models with varying density or affinity |
How to Study the receptor internalization Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Fluorescence microscopy | Receptor localization and movement from plasma membrane to endocytic vesicles | Visualizing internalization and sorting |
| Live-cell imaging | Dynamics of receptor internalization after ligand stimulation | Time-course internalization studies |
| Biochemical fractionation | Distribution of receptors among membrane and endosomal fractions | Trafficking route analysis |
| Proteomics | Posttranslational modifications and interacting endocytic proteins | Identifying regulators of internalization |
| CRISPR knockout screening | Genes required for receptor internalization | Functional genomics of endocytic machinery |
| Viral entry assay | Pathogen internalization via receptor-mediated endocytosis | Host factor and viral entry studies |
| Particle uptake assay | Efficiency of receptor-mediated endocytosis as a function of receptor properties | Quantitative internalization modeling |
| Receptor recycling assay | Return of internalized receptors to the plasma membrane | Recycling versus degradation studies |
Imaging-based internalization assays
Fluorescence microscopy and live-cell imaging of tagged receptors allow direct visualization of receptor movement from the plasma membrane to endocytic vesicles. Tagged knock-in models enable tracking of receptor internalization and sorting to lysosomes or recycling endosomes. Imaging is often combined with ligand stimulation to trigger monoubiquitination and internalization.
Biochemical and proteomic analysis of receptor trafficking
Biochemical fractionation and proteomic approaches can identify endocytic proteins and posttranslational modifications associated with receptor internalization. Analysis of ubiquitination and phosphorylation states of GPCRs helps define the regulatory code for internalization. These methods are complementary to imaging and can reveal receptor-specific machinery requirements.
Genetic screens and functional genomics
CRISPR-based knockout screens can identify genes required for receptor internalization and endocytic trafficking. Candidate endocytic proteins can be validated by targeted knockout followed by quantitative internalization assays. Such screens link receptor internalization to broader cellular pathways and disease-relevant processes.
Viral entry and pathogen internalization assays
Because transferrin receptor protein 1 cooperates with mGluR2 to mediate rabies virus and SARS-CoV-2 internalization, viral entry assays can be used to study receptor internalization pathways. These assays connect receptor-mediated endocytosis to host-pathogen interactions. Chemokine receptor internalization assays similarly provide readouts for receptor trafficking in immune contexts.
How CRISPR Can Be Used to Study GO:0031623 receptor internalization
Knockout
CRISPR knockout cell models can remove candidate endocytic or receptor genes to test whether they are required for receptor internalization. For example, knocking out endocytic proteins provides insight into the mechanisms of GPR15 receptor internalization. Knockout of receptors themselves can reveal their contribution to ligand-induced internalization and downstream trafficking.
Point Mutation
Point-mutation models can alter specific ubiquitination or phosphorylation sites on receptors or regulatory proteins to test their role in internalization. Because monoubiquitination following ligand-induced activation initiates internalization, mutation of the modified residue can block or enhance the process. Such models help distinguish initiation signals from downstream trafficking steps.
Knock-in
Knock-in of tagged receptors allows tracking of internalization, lysosomal degradation and recycling in a physiologically expressed context. Tagged knock-in models are useful for imaging receptor movement from the plasma membrane to endocytic vesicles. They can also be combined with disease-relevant mutations to study altered trafficking.
Overexpression
Overexpression of receptors or endocytic proteins can enhance or saturate internalization pathways and reveal rate-limiting components. Receptor properties such as density and affinity influence particle internalization through receptor-mediated endocytosis, making overexpression a useful tool for quantitative studies. Overexpression models complement knockout and knock-in approaches for dissecting receptor internalization mechanisms.
How EDITGENE Supports receptor internalization Research
Researchers studying receptor internalization-related genes often need to determine whether a candidate gene is causally involved in receptor trafficking, endocytic uptake or downstream sorting. EDITGENE provides CRISPR-based cell model services that enable functional dissection of receptor internalization pathways, from gene knockout to precise point mutations, tagged knock-ins, overexpression and library screening.
Contact EDITGENE today to design your custom CRISPR model for receptor internalization research.
Frequently Asked Questions About receptor internalization
What is receptor internalization GO:0031623?
GO:0031623 receptor internalization is a receptor-mediated endocytosis process that moves receptors from the plasma membrane to the inside of the cell, beginning with monoubiquitination after ligand-induced activation and ending with lysosomal/vacuolar degradation or recycling to the plasma membrane.
What genes are involved in receptor internalization?
Genes and proteins implicated in receptor internalization include chemokine receptors such as CXCR4 and CCR5, AGTR1, OPRD1, EDNRA, GPR15, GRM2, TFRC, ubiquitin precursors, GRK2, arrestins, clathrin, AP-2 subunits and RAB GTPases.
How does receptor internalization start?
It starts when cell surface receptors are monoubiquitinated following ligand-induced activation, after which receptors are taken up into endocytic vesicles.
What happens to receptors after internalization?
Internalized receptors are either targeted to the lysosome or vacuole for degradation or recycled back to the plasma membrane.
Which receptors are known to internalize?
Examples include chemokine receptors, angiotensin II receptor, delta-opioid receptor, type-A endothelin receptor, GPR15 and mGluR2.
How is receptor internalization regulated?
It is regulated by posttranslational modifications such as ubiquitination and phosphorylation of GPCRs, and by receptor properties such as density and affinity.
Why is receptor internalization important in disease?
It affects opioid receptor biology, cardiovascular receptor signaling and viral entry by rabies virus and SARS-CoV-2, making it relevant to neuropsychiatric, cardiovascular and infectious disease research.
What methods are used to study receptor internalization?
Common methods include fluorescence microscopy, live-cell imaging, biochemical fractionation, proteomics, CRISPR knockout screening, viral entry assays and particle uptake assays.
Can CRISPR be used to study receptor internalization?
Yes, CRISPR knockout, point-mutation, knock-in and overexpression models can test the role of specific genes and residues in receptor internalization and trafficking.
What is the difference between receptor internalization and receptor-mediated endocytosis?
Receptor internalization is a receptor-mediated endocytosis process specifically resulting in movement of receptors from the plasma membrane to the inside of the cell, often followed by degradation or recycling.
Conclusion
GO:0031623 receptor internalization is a defined biological process that moves activated, monoubiquitinated receptors from the plasma membrane into endocytic vesicles, where they are sorted for degradation or recycling. Its mechanistic study spans GPCR biology, chemokine signaling, cardiovascular receptors, opioid receptors and viral entry, with receptor-specific endocytic machinery requirements. CRISPR-based knockout, point-mutation, knock-in and overexpression models provide a direct route to test causal roles of genes and modifications in this process.
References
- 1. Neel NF et al.. 2005. Chemokine receptor internalization and intracellular trafficking.. Cytokine Growth Factor Rev 16(6):637-58 PMID: 15998596
- 2. Billah MM et al.. 2023. Effects of receptor properties on particle internalization through receptor-mediated endocytosis.. Soft Matter 19(31):5907-5915 PMID: 37483086
- 3. Hunyady L. 1999. Molecular mechanisms of angiotensin II receptor internalization.. J Am Soc Nephrol 10 Suppl 11:S47-56 PMID: 9892140
- 4. Tang X et al.. 2022. Posttranslational modifications in GPCR internalization.. Am J Physiol Cell Physiol 323(1):C84-C94 PMID: 35613355
- 5. Eisinger DA et al.. 2005. Mechanism and consequences of delta-opioid receptor internalization.. Crit Rev Neurobiol 17(1):1-26 PMID: 16307525
- 6. Wang X et al.. 2023. Transferrin Receptor Protein 1 Cooperates with mGluR2 To Mediate the Internalization of Rabies Virus and SARS-CoV-2.. J Virol 97(2):e0161122 PMID: 36779763
- 7. Deng Y et al.. 2023. Endocytic proteins mediating GPR15 receptor internalization provide insight into the underlying mechanisms.. FEBS Lett 597(11):1528-1540 PMID: 37051832
- 8. Wang J et al.. 2000. Internalization of type-A endothelin receptor.. J Cardiovasc Pharmacol 36(5 Suppl 1):S61-5 PMID: 11078337
