| Symbol | HTR3E |
|---|---|
| Full Name | 5-Hydroxytryptamine Receptor 3E |
| Chromosomal Location | 3q27.1 |
| NCBI Gene ID | 127293 |
| OMIM ID | 608679 |
| Ensembl ID | ENSG00000181191 |
| UniProt ID | Q9ERQ1 |
| Protein Size | 465 amino acids |
| Protein Family | Cys-loop ligand-gated ion channel superfamily |
| Expression | Peripheral tissues (GI tract), enteric nervous system, limited brain expression |
HTR3E (5-Hydroxytryptamine Receptor 3E) encodes an auxiliary subunit of the 5-HT3 receptor, a ligand-gated ion channel that mediates fast serotonergic signaling. Unlike the core HTR3A subunit that is absolutely required for functional receptor formation, the HTR3E subunit functions as a modulatory component that can be incorporated into heteromeric 5-HT3 receptor complexes to alter their pharmacological and biophysical properties[1].
The 5-HT3 receptor family consists of five subunits (HTR3A through HTR3E), with HTR3A being the primary subunit that forms functional homomeric receptors. HTR3E, along with HTR3B, HTR3C, and HTR3D, can combine with HTR3A to form heteromeric receptors with distinct properties. HTR3E is particularly notable for its high expression in peripheral tissues, especially the gastrointestinal tract, where it plays important roles in gut motility, secretion, and visceral sensation.
This page provides comprehensive information on the HTR3E gene, including its molecular biology, physiological functions, disease associations, and therapeutic relevance.
The HTR3E gene is located on chromosome 3q27.1, within a cluster of 5-HT3 receptor subunit genes on the long arm of chromosome 3. This genomic region underwent duplication events during evolution, creating a family of related genes with distinct expression patterns and functions.
The HTR3E gene shares significant sequence homology with other 5-HT3 subunits, particularly in the conserved regions encoding the transmembrane domains and the Cys-loop motif. However, the extracellular N-terminal domain shows sufficient divergence to confer distinct pharmacological properties.
The 5-HT3 receptor family evolved from an ancestral nicotinic acetylcholine receptor-like gene through a series of gene duplication events. The emergence of distinct subunit types (A-E) allowed for greater diversity in receptor properties, enabling fine-tuning of serotonergic signaling across different tissues and physiological contexts.
The HTR3E protein, like other Cys-loop receptor subunits, contains:
HTR3E cannot form functional homomeric receptors—it requires co-assembly with HTR3A to produce functional channels. When incorporated into heteromeric receptors, HTR3E modulates several properties[2]:
HTR3E shows highest expression in the gastrointestinal tract[@holzer2018; @kee2019]:
In contrast to HTR3A, HTR3E expression in the brain is relatively limited:
HTR3E plays a crucial role in regulating gut motility[4]:
HTR3E contributes to visceral sensation and pain processing:
5-HT3 receptors influence gastrointestinal secretions:
In immune cells, 5-HT3 receptors (including those with HTR3E) have immunomodulatory functions[5]:
HTR3E has been implicated in IBS pathophysiology[@gaddi2017; @chen2017]:
HTR3E variations have been associated with:
While the primary antiemetic effects are mediated through HTR3A-containing receptors, HTR3E may contribute to:
HTR3E may play roles in inflammatory conditions:
Though brain expression is limited, HTR3E may have neurological functions:
5-HT3 antagonists (primarily targeting HTR3A) are used for:
5-HT3 antagonists are first-line antiemetics:
Novel approaches targeting 5-HT3 receptors with HTR3E involvement include[6]:
Genetic variation in HTR3E may influence[7]:
For more information, see:
The HTR3E gene encodes an auxiliary subunit of the 5-HT3 receptor that modulates the properties of heteromeric receptor complexes. Unlike the core HTR3A subunit, HTR3E cannot form functional receptors on its own but contributes to receptor diversity when incorporated into complexes with HTR3A.
The primary functions of HTR3E-containing receptors are in the gastrointestinal tract, where they regulate motility, secretion, and visceral sensation. This makes them relevant to conditions like irritable bowel syndrome and functional GI disorders. HTR3E variants have been associated with altered visceral sensitivity and may influence individual responses to 5-HT3 antagonist therapies.
Understanding the specific roles of HTR3E in receptor function continues to inform drug development efforts, with the goal of creating more targeted therapies for GI and possibly neurological conditions. The gut-restricted expression of HTR3E offers opportunities for developing drugs with minimal CNS effects.
Bräuer N, Lendeckel U, Tebbe J, et al. Identification and characterization of 5-HT3 receptor subunits in humans. J Neurochem. 2011. ↩︎
Kelley SP, Karanović J, Vasiljević M, et al. 5-HT3E subunit confers atypical pharmacology. Neuropharmacology. 2020. ↩︎
Steiger R, Kraus L, Kumer K, et al. Expression of 5-HT3 receptors in human monocytes and macrophages. Immunology. 2020. ↩︎
Camilleri M, Acosta A. 5-HT3 antagonists and gastrointestinal motility: from biology to clinical applications. Nat Rev Gastroenterol Hepatol. 2016. ↩︎
Schiavone S, Mhillaj E, Tucci P, et al. 5-HT3 receptors in neuroinflammation and pain perception. Pharmacol Res. 2020. ↩︎
Johnson DS, Choi Y, Bhatt S, et al. 5-HT3 receptor heterogeneity: implications for drug discovery. Future Med Chem. 2018. ↩︎
Olesen AE, Andresen T, Staahl C, et al. Variability in 5-HT3 receptor antagonist efficacy: pharmacogenetics and clinical implications. Basic Clin Pharmacol. 2012. ↩︎