5-hydroxytryptamine receptor 3A subunit (5-HT3A)

The 5-hydroxytryptamine receptor 3A subunit (5-HT3A) is a protein that, together with other 5-HT3 subunits, forms the functional 5-HT3 receptor, a ligand-gated cation-selective ion channel of the Cys-loop superfamily. It uniquely mediates fast excitatory neurotransmission by opening in response to serotonin (5-HT) binding, allowing the rapid influx of sodium, potassium, and to some extent calcium ions through the cell membrane, ultimately leading to neuronal depolarization. The 5-HT3A subunit is essential for receptor function: either as a homopentamer (five 5-HT3A subunits) or as the required component in heteropentameric complexes with other related subunits (5-HT3B, C, D, or E). Pharmacologically, the 5-HT3 receptor is notable as the target of several potent antiemetic drugs (“setrons,” such as ondansetron) used to treat nausea and vomiting, especially in cancer and post-surgical patients. It is uniquely not a G-protein coupled receptor (unlike most serotonin receptor subtypes), but rather directly forms an ion channel. Its function and pharmacology are further influenced by alternative subunit composition, post-translational modification (e.g., glycosylation), and interaction with intracellular proteins. Overall, the 5-HT3A subunit is central both to basic neurotransmission and to drug action in the nervous and gastrointestinal systems.

Other names

5-HT3A5-HT3 receptor A subunitSerotonin receptor 3A subunitHTR3A5-hydroxytryptamine type 3A receptor

Competitive antagonism at the 5-HT3 (ligand-binding) site; Blockade of serotonin-induced opening of the ion channel, inhibiting depolarization and neuronal firing