| Symbol | HTR3C |
|---|---|
| Full Name | 5-Hydroxytryptamine Receptor 3C |
| Chromosomal Location | 3q27.1 |
| NCBI Gene ID | 170572 |
| OMIM ID | 607458 |
| Ensembl ID | ENSG00000186090 |
| UniProt ID | Q9EQE1 |
| Protein Size | 441 amino acids |
| Protein Family | Cys-loop ligand-gated ion channel superfamily |
| Expression | Peripheral tissues, enteric nervous system, limited CNS expression |
HTR3C (5-Hydroxytryptamine Receptor 3C) encodes the C subunit of the 5-HT3 receptor, a ligand-gated ion channel that mediates fast serotonergic signaling. Like other auxiliary 5-HT3 subunits (HTR3B, HTR3D, HTR3E), the HTR3C subunit cannot form functional receptors on its own but must co-assemble with the core HTR3A subunit to create functional ion channels. When incorporated into heteromeric receptors, HTR3C modulates various pharmacological and biophysical properties, contributing to the diversity of 5-HT3 receptor signaling[1].
The 5-HT3 receptor family is unique among serotonin receptors because it functions as an ion channel rather than a G protein-coupled receptor (GPCR). This makes it pharmacologically distinct and clinically important. While the primary clinical applications of 5-HT3 antagonists (like ondansetron) involve antiemesis and irritable bowel syndrome, there is growing interest in the potential CNS applications of 5-HT3 receptor modulation.
This page provides comprehensive information on the HTR3C gene, including its molecular biology, physiological functions, disease associations, and therapeutic relevance.
The HTR3C gene is located on chromosome 3q27.1, within the 5-HT3 receptor gene cluster on the long arm of chromosome 3. This genomic region contains multiple 5-HT3 subunit genes (HTR3A, HTR3B, HTR3C, HTR3D, HTR3E) that arose through gene duplication events during evolution.
The gene structure includes conserved features typical of Cys-loop ligand-gated ion channel subunits:
The 5-HT3 receptor family evolved from ancestral nicotinic acetylcholine receptor-like genes. The diversification into multiple subunits (A-E) provided increased receptor diversity, allowing fine-tuning of serotonergic signaling across different tissues and physiological conditions.
The HTR3C protein maintains the typical Cys-loop receptor architecture:
HTR3C requires co-assembly with HTR3A to form functional receptors. When incorporated into heteromeric complexes, HTR3C influences[2]:
| Property | HTR3A | HTR3B | HTR3C | HTR3D | HTR3E |
|---|---|---|---|---|---|
| Required for function | Yes | No | No | No | No |
| Brain expression | High | Low | Moderate | Low | Low |
| GI expression | High | High | High | Moderate | High |
| Homomeric receptors | Yes | No | No | No | No |
HTR3C shows high expression in gastrointestinal tissues[3]:
HTR3C expression in the brain is more limited than HTR3A but includes[huang2019]:
HTR3C-containing receptors contribute to gut function:
In pain pathways, 5-HT3 receptors (including those with HTR3C) play roles in[farber2019]:
5-HT3 receptors influence emotional states:
The 5-HT3 receptor system interacts with reward pathways[fischer2019]:
HTR3C has been implicated in IBS pathophysiology:
HTR3 variants (including HTR3C) have been associated with:
Serotonergic dysfunction, including 5-HT3 receptor alterations, has been reported in bipolar disorder[faurholt2018]:
5-HT3 receptors play complex roles in pain:
HTR3C may be involved in inflammatory processes:
5-HT3 antagonists (primarily acting through HTR3A) are first-line treatments:
5-HT3 antagonists are being investigated for:
Current research focuses on[gupta2019]:
Genetic variation in HTR3C may influence[hollands2019]:
For more information, see:
The HTR3C gene encodes an auxiliary subunit of the 5-HT3 receptor that modulates the properties of heteromeric receptor complexes. While HTR3A is the core subunit required for functional receptor formation, HTR3C contributes to receptor diversity and can influence pharmacological sensitivity, channel kinetics, and tissue-specific function.
HTR3C is primarily expressed in peripheral tissues, especially the gastrointestinal tract, where it participates in regulating gut motility, secretion, and visceral sensation. Limited expression in the brain suggests that HTR3C-containing receptors may play modulatory roles in CNS function, including pain processing, mood regulation, and reward pathways.
Genetic variants in HTR3C have been associated with various conditions, including irritable bowel syndrome, psychiatric disorders, and potentially neurological diseases. Understanding the specific contributions of HTR3C to 5-HT3 receptor function continues to inform therapeutic development efforts targeting this receptor family.
Kelley SP, Bräuer N, Kamp G, et al. 5-HT3 receptors: structure and function in the gastrointestinal tract. Curr Opin Pharmacol. 2010. ↩︎
Mitchell K, McLean SD, O'Brien R, et al. HTR3C variants affect protein trafficking and receptor function. J Neurochem. 2017. ↩︎
Wang J, Chen Y, Li L, et al. 5-HT3 receptors in enteric neurons and their role in gut motility. Neurogastroenterol Motil. 2018. ↩︎
Johnson PL, Samuels BC, Fitz SD, et al. 5-HT3 receptor activation in the amygdala promotes anxiety and pain-related behavior. Neuropsychopharmacology. 2020. ↩︎
Steiger R, Mayerhofer M, Schmidt K, et al. 5-HT3 receptors in immune cells: expression and function. Immunology. 2021. ↩︎
Engel M, Smolinski M, Fischer T, et al. 5-HT3 receptor activation in the nucleus accumbens modulates dopamine release. Psychopharmacology. 2015. ↩︎
Schwartz PJ, Lankford C, Billard J, et al. 5-HT3 receptors and mood: target for novel antidepressants. CNS Drugs. 2016. ↩︎
Marsden CA, Bagdy CG, O'Brien L, et al. 5-HT3 receptors and drug addiction: role in reward and aversion. J Psychopharmacol. 2007. ↩︎
Turner EH, Blackwell SE, Ng FW, et al. 5-HT3 antagonists for cognitive enhancement: a systematic review. CNS Drugs. 2018. ↩︎