GO:0016497 substance K receptor activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016497 substance K receptor activity is a molecular function defined as combining with substance K (neurokinin A), a decapeptide His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met, to initiate a change in cell activity.
• The receptor responsible for this activity is primarily the tachykinin NK2 receptor (TACR2/NK2R), which belongs to the G protein-coupled receptor superfamily and preferentially binds substance K.
• Substance K receptor activity mediates smooth muscle contraction, neurotransmitter release, and inflammatory responses in peripheral tissues, and its dysfunction is linked to gastrointestinal, respiratory, and neurological disorders.
• Pharmacological characterization using selective agonists and antagonists has been essential to distinguish NK2 receptor activity from NK1 and NK3 receptors.
• CRISPR-based knockout, point mutation, and knock-in models of TACR2 enable causal dissection of substance K signaling in health and disease.
• EDITGENE provides comprehensive CRISPR services including TACR2 knockout, point mutation, knock-in, overexpression, and library screening to accelerate substance K receptor research.
Description
Substance K receptor activity (GO:0016497) is a molecular function that mediates cellular responses to the tachykinin peptide substance K, also known as neurokinin A. This decapeptide (His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met) acts as a neurotransmitter and neuromodulator in the central and peripheral nervous systems. The receptor that primarily recognizes substance K is the neurokinin 2 receptor (NK2R), encoded by the TACR2 gene, a member of the G protein-coupled receptor (GPCR) family. Understanding this activity is crucial because tachykinin signaling regulates smooth muscle contraction, exocrine secretion, and inflammatory processes, and its dysregulation has been implicated in diseases such as asthma, irritable bowel syndrome, and glioblastoma. Researchers studying substance K receptor activity seek to elucidate its precise signaling mechanisms, identify selective pharmacological tools, and develop therapeutic strategies targeting this pathway.
substance K receptor activity At A Glance
| GO ID | GO:0016497 |
|---|---|
| GO term | substance K receptor activity |
| Ontology | molecular_function |
| Synonym | neurokinin A receptor activity, neuromedin L receptor activity |
| Major function | Binding to substance K (neurokinin A) to initiate intracellular signaling |
| Primary receptor | Tachykinin NK2 receptor (TACR2/NK2R) |
| Ligand | Substance K (neurokinin A), a decapeptide His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met |
| Signaling mechanism | G protein-coupled receptor activation, typically Gq/11-mediated phospholipase C signaling |
| Tissue distribution | Smooth muscle, gastrointestinal tract, respiratory tract, and central nervous system |
What Is GO:0016497?
According to the Gene Ontology, substance K receptor activity (GO:0016497) is defined as the function of combining with substance K, a peptide with the sequence His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met, to initiate a change in cell activity. This activity is synonymous with neurokinin A receptor activity and neuromedin L receptor activity. It represents the initial molecular event in a signaling cascade that translates extracellular substance K binding into intracellular responses, typically through G protein-coupled receptor activation.
Why Is substance K receptor activity Important in Cell Biology?
Substance K receptor activity is a critical mediator of tachykinin signaling, which regulates a wide range of physiological processes including smooth muscle contraction, neurotransmission, and inflammation. Dysregulation of this activity has been implicated in various pathological conditions, such as gastrointestinal motility disorders, respiratory diseases, and certain cancers. Therefore, understanding the molecular details of substance K receptor activity is essential for developing targeted therapies and for interpreting pharmacological studies that use tachykinin receptor agonists and antagonists.
• Regulates smooth muscle contraction in the gastrointestinal and respiratory tracts.
• Modulates neurotransmitter release and neurogenic inflammation.
• Involved in pain perception and central nervous system signaling.
• Implicated in gastrointestinal motility disorders such as irritable bowel syndrome.
• Contributes to respiratory diseases including asthma and chronic obstructive pulmonary disease.
• Potential target in glioblastoma and other cancers.
• Key to understanding tachykinin receptor selectivity and drug development.
• Provides a model for studying GPCR pharmacology and signal transduction.
• Enables research on gender-related differences in receptor expression and activity.
• Facilitates development of selective NK2 receptor antagonists for therapeutic use.
What Happens During substance K receptor activity?
Ligand Binding and Receptor Activation
In simple terms: Substance K binds to its receptor on the cell surface, like a key fitting into a lock.
Substance K (neurokinin A) is released from neurons or other cells and binds to the NK2 receptor (TACR2) with high affinity. This binding induces a conformational change in the receptor, activating it. The receptor is a member of the tachykinin receptor family, which also includes NK1 and NK3 receptors, but NK2 exhibits preferential binding for substance K over other tachykinins.
G Protein Activation and Second Messenger Signaling
In simple terms: The activated receptor turns on a G protein, which then triggers a cascade of signals inside the cell.
Upon activation, the NK2 receptor interacts with heterotrimeric G proteins, primarily of the Gq/11 family. This leads to the activation of phospholipase C, which hydrolyzes phosphatidylinositol 4,5-bisphosphate into inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 triggers calcium release from intracellular stores, while DAG activates protein kinase C. These second messengers propagate the signal to downstream effectors.
Cellular Responses and Physiological Effects
In simple terms: The signaling cascade causes the cell to respond, such as contracting or releasing substances.
The rise in intracellular calcium and activation of protein kinase C lead to various cellular responses, including smooth muscle contraction, secretion, and gene expression changes. In the gastrointestinal tract, substance K receptor activity stimulates motility. In the respiratory system, it contributes to bronchoconstriction and mucus secretion. In the nervous system, it modulates neurotransmitter release and pain transmission.
Receptor Desensitization and Internalization
In simple terms: After signaling, the receptor is turned off and brought inside the cell to prevent overstimulation.
Prolonged exposure to substance K leads to receptor desensitization, mediated by phosphorylation of the receptor by G protein-coupled receptor kinases (GRKs) and subsequent binding of arrestins. This promotes receptor internalization and recycling or degradation, thereby terminating the signal. This regulatory mechanism is crucial for maintaining responsiveness and preventing pathological overactivation.
Key Genes Involved in GO:0016497 substance K receptor activity
The following genes and proteins are key components of substance K receptor activity and its signaling pathway.
| Gene | Major Role | Research Relevance |
|---|---|---|
| TACR2 | Encodes the NK2 receptor, the primary receptor for substance K | Main target for knockout, point mutation, and knock-in studies |
| TAC1 | Encodes the precursor protein for substance K (neurokinin A) and substance P | Ligand production and processing |
| TACR1 | Encodes the NK1 receptor, which binds substance P with high affinity | Cross-reactivity and selectivity studies |
| TACR3 | Encodes the NK3 receptor, which binds neurokinin B | Family comparison and pharmacological profiling |
| GNAQ | Encodes the Gq alpha subunit | Mediates NK2 receptor signaling to phospholipase C |
| GNA11 | Encodes the G11 alpha subunit | Alternative G protein for NK2 signaling |
| PLCB1 | Encodes phospholipase C beta 1 | Key effector enzyme in NK2 signaling |
| PRKCA | Encodes protein kinase C alpha | Downstream mediator of DAG signaling |
| ITPR1 | Encodes inositol 1,4,5-trisphosphate receptor | Mediates calcium release from ER |
| ARRB1 | Encodes beta-arrestin 1 | Receptor desensitization and internalization |
| ARRB2 | Encodes beta-arrestin 2 | Receptor desensitization and internalization |
| GRK2 | Encodes G protein-coupled receptor kinase 2 | Phosphorylates activated NK2 receptor |
| GRK3 | Encodes G protein-coupled receptor kinase 3 | Phosphorylates activated NK2 receptor |
| CALM1 | Encodes calmodulin 1 | Calcium signaling mediator |
| MAPK1 | Encodes ERK2 | Downstream kinase in NK2 signaling |
| MAPK3 | Encodes ERK1 | Downstream kinase in NK2 signaling |
| NFKB1 | Encodes NF-kappa-B p105 subunit | Inflammatory gene expression |
How Is substance K receptor activity Regulated?
Substance K receptor activity is regulated at multiple levels. Receptor expression levels can be modulated by transcriptional and post-transcriptional mechanisms, as evidenced by gender-related differences in NK2 receptor expression in human colonic smooth muscle. Agonist-induced desensitization and internalization, mediated by GRKs and arrestins, provide rapid feedback regulation. Additionally, the activity of the receptor can be influenced by interactions with other proteins and by post-translational modifications. Pharmacological studies have identified selective antagonists that can block NK2 receptor activity, offering tools to study its regulation. The signaling pathway is also subject to cross-talk with other GPCR pathways and growth factor signaling cascades.
substance K receptor activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| TACR2 | Irritable bowel syndrome, gastrointestinal dysmotility | TACR2 knockout mouse or human intestinal organoids |
| TACR2 | Asthma, COPD | TACR2 knockout or point-mutant airway smooth muscle cells |
| TACR2 | Glioblastoma | TACR2 overexpression in glioblastoma cell lines |
| TAC1 | Pain and neurogenic inflammation | TAC1 knockout mice or sensory neuron cultures |
| TACR1 | Depression, anxiety, emesis | TACR1 knockout or knock-in models |
Gastrointestinal Disorders
Substance K receptor activity plays a key role in regulating gastrointestinal motility. Altered NK2 receptor expression and activity have been observed in colonic smooth muscle, with gender-related differences that may contribute to conditions such as irritable bowel syndrome (IBS) and other motility disorders. NK2 receptor antagonists are being investigated for the treatment of IBS and related diseases.
Respiratory Diseases
In the respiratory tract, substance K receptor activity contributes to bronchoconstriction, mucus secretion, and inflammation. Overactivation of this pathway is implicated in asthma and chronic obstructive pulmonary disease (COPD). NK2 receptor antagonists have been explored as potential therapies for these conditions.
Cancer
Tachykinin receptors, including NK2, are expressed in various cancers. Substance K receptor activity may promote tumor cell proliferation and survival. For example, a potential glioblastoma-targeted therapy using a substance P analog has been studied, highlighting the relevance of tachykinin receptor selectivity in cancer. Further research is needed to fully elucidate the role of NK2 in cancer.
Neurological and Inflammatory Conditions
Substance K acts as a neurotransmitter and modulator in the central and peripheral nervous systems. Its receptor activity is involved in neurogenic inflammation and pain transmission. Dysregulation may contribute to neuroinflammatory diseases and chronic pain syndromes. Additionally, substance P, a related tachykinin, has been shown to stimulate PPAR-gamma expression in human monocytes and macrophages, suggesting a role in inflammation resolution.
From substance K receptor activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does TACR2 mediate substance K-induced smooth muscle contraction? | TACR2 knockout smooth muscle cells or tissues |
| What is the role of specific TACR2 residues in ligand binding? | TACR2 point-mutation knock-in cell lines |
| How does TACR2 signaling contribute to inflammation? | TACR2 overexpression in immune cells |
| Can TACR2 be tagged for live-cell imaging? | TACR2 tagged knock-in (e.g., GFP) cell lines |
| What are the downstream effectors of TACR2 activation? | TACR2 knockout followed by phosphoproteomics |
| Does TACR2 expression correlate with disease severity? | Patient-derived organoids with TACR2 knockout |
How to Study the substance K receptor activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radioligand binding | Receptor affinity and density | Characterizing NK2 receptor pharmacology |
| Calcium mobilization assay | Intracellular calcium release | Functional activation of NK2 receptor |
| IP3 assay | Inositol trisphosphate production | Gq-coupled signaling |
| CRISPR knockout | Loss of receptor function | Determining causal role of TACR2 |
| CRISPR point mutation | Effect of specific amino acid changes | Mapping ligand-binding sites |
| RNA-seq | Transcriptional changes | Identifying downstream target genes |
| Proteomics | Protein expression and modifications | Discovering signaling effectors |
Pharmacological Characterization
Selective agonists and antagonists are used to characterize substance K receptor activity. For example, NK2 receptor antagonists can block substance K-induced responses, helping to distinguish NK2 from NK1 and NK3 receptors. Radioligand binding assays with iodinated substance K or selective antagonists can determine receptor affinity and density.
Signal Transduction Assays
Measurements of intracellular calcium mobilization, IP3 production, and PKC activation are standard methods to assess substance K receptor activity. These assays can be performed in cell lines expressing recombinant NK2 receptor or in primary cells. Reporter gene assays driven by calcium-responsive elements can also be used.
Genetic Manipulation and CRISPR
CRISPR/Cas9-mediated knockout of TACR2 allows the study of loss-of-function phenotypes. Point mutations can be introduced to dissect ligand-binding residues or phosphorylation sites. Knock-in of tagged receptors enables imaging and biochemical purification. Overexpression models help study gain-of-function effects.
Transcriptomic and Proteomic Profiling
RNA-seq and proteomics can reveal downstream transcriptional and signaling changes following substance K receptor activation. For instance, gender-related differences in NK2 receptor expression were identified using molecular techniques. Phosphoproteomics can identify novel substrates of NK2 receptor signaling.
How CRISPR Can Be Used to Study GO:0016497 substance K receptor activity
Knockout
CRISPR/Cas9 knockout of TACR2 creates cell models lacking substance K receptor activity. These models are essential to confirm that observed responses to substance K are specifically mediated by NK2 receptor. Knockout cells can be used in contraction assays, calcium imaging, and downstream signaling studies.
Point Mutation
Point mutations in TACR2 can be introduced to study the role of specific amino acids in ligand binding, G protein coupling, or desensitization. For example, mutating putative phosphorylation sites can reveal their importance in receptor internalization. These models provide fine-grained mechanistic insights.
Knock-in
Knock-in of tagged TACR2 (e.g., with GFP or HA epitope) allows real-time visualization and biochemical isolation of the receptor. This approach is valuable for studying receptor trafficking, localization, and interaction partners. Knock-in of disease-associated mutations can also model human conditions.
Overexpression
Overexpression of TACR2 in cell lines such as HEK293 or CHO cells provides a robust system for pharmacological and signaling studies. It enhances signal-to-noise ratio in assays and allows investigation of gain-of-function effects. Overexpression models are also used for high-throughput screening of receptor antagonists.
How EDITGENE Supports substance K receptor activity Research
Researchers studying substance K receptor activity-related genes often need to determine whether a candidate gene is causally involved in a specific signaling pathway or disease phenotype. EDITGENE provides a comprehensive suite of CRISPR-based services to enable precise genetic manipulation of TACR2 and related genes, accelerating discovery in tachykinin biology.
Contact EDITGENE today to design your custom CRISPR model for substance K receptor activity research.
Frequently Asked Questions About substance K receptor activity
What is substance K receptor activity?
Substance K receptor activity (GO:0016497) is the molecular function of binding to substance K (neurokinin A) to initiate a change in cell activity, primarily mediated by the NK2 receptor (TACR2).
What genes are involved in substance K receptor activity?
The primary gene is TACR2, which encodes the NK2 receptor. Other related genes include TAC1 (ligand precursor), TACR1, TACR3, and downstream signaling molecules like GNAQ and PLCB1.
Which receptor binds substance K?
The tachykinin NK2 receptor (TACR2/NK2R) preferentially binds substance K (neurokinin A).
What is the difference between substance K and substance P?
Substance K (neurokinin A) and substance P are related tachykinin peptides with different receptor preferences: substance P binds NK1 receptor, while substance K binds NK2 receptor.
What diseases are associated with substance K receptor activity?
Dysregulation is linked to gastrointestinal motility disorders, respiratory diseases like asthma, and potentially cancer including glioblastoma.
How can I study substance K receptor activity in the lab?
Common methods include radioligand binding, calcium mobilization assays, and CRISPR-based genetic manipulation of TACR2.
What are NK2 receptor antagonists?
NK2 receptor antagonists are compounds that block substance K receptor activity and are investigated for treating conditions like irritable bowel syndrome and asthma.
Is substance K receptor activity involved in inflammation?
Yes, it contributes to neurogenic inflammation and can modulate inflammatory responses in various tissues.
Are there gender differences in substance K receptor activity?
Yes, studies have shown gender-related differences in NK2 receptor expression and activity in human colonic smooth muscle.
How does CRISPR help study substance K receptor activity?
CRISPR allows knockout, point mutation, knock-in, and overexpression of TACR2, enabling precise dissection of its function in health and disease.
Conclusion
Substance K receptor activity (GO:0016497) is a fundamental molecular function mediated primarily by the NK2 receptor (TACR2), which plays diverse roles in physiology and disease. Understanding its mechanisms, regulation, and genetic underpinnings is essential for developing targeted therapies for gastrointestinal, respiratory, and neurological disorders. CRISPR-based models offer powerful tools to dissect this pathway, and EDITGENE provides comprehensive services to support such research.
References
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- 2. Regoli D et al.. 1987. Pharmacological receptors for substance P and neurokinins.. Life Sci 40(2):109-17 PMID: 2432376
- 3. Datar P et al.. 2004. Substance P: structure, function, and therapeutics.. Curr Top Med Chem 4(1):75-103 PMID: 14754378
- 4. Regoli D et al.. 1989. Receptors for substance P and related neurokinins.. Pharmacology 38(1):1-15 PMID: 2542998
- 6. Amoruso A et al.. 2008. A novel activity for substance P: stimulation of peroxisome proliferator-activated receptor-gamma protein expression in human monocytes and macrophages.. Br J Pharmacol 154(1):144-52 PMID: 18278062
- 7. Jung HJ et al.. 2021. Tachykinin NK(2) antagonist for treatments of various disease states.. Auton Neurosci 235:102865 PMID: 34358844
- 8. Drimousis S et al.. 2020. Gender-Related Differences of Tachykinin NK(2) Receptor Expression and Activity in Human Colonic Smooth Muscle.. J Pharmacol Exp Ther 375(1):28-39 PMID: 32764152
