HTR3B Gene - 5-HT3B Serotonin Receptor Subunit

HTR3B encodes the B subunit of the 5-hydroxytryptamine receptor 3 (5-HT3), a pentameric ligand-gated ion channel that mediates fast excitatory neurotransmission in the central and peripheral nervous systems. The B subunit co-assembles with the A subunit to form functional heteromeric channels with distinct pharmacological and biophysical properties. HTR3B is expressed in brain regions such as the hippocampus and cortex, as well as in gastrointestinal neurons. Variants in HTR3B have been associated with psychiatric disorders, irritable bowel syndrome, and chemotherapy-induced nausea.

Tissue Expression

Cell Line Expression

Hotspot Mutations

Mutation functional classification

• Serotonergic synapse (KEGG: hsa04726)

• Neuroactive ligand-receptor interaction (KEGG: hsa04080)

• 5-HT3 receptor signaling (Reactome: R-HSA-375280)

The 5-HT3B protein (UniProt O95264) is a 441-amino acid subunit of the 5-HT3 receptor. It contains four transmembrane domains (M1-M4) and a large extracellular N-terminal domain that contributes to ligand binding. Unlike the homomeric 5-HT3A receptor, the heteromeric 5-HT3AB channel exhibits larger single-channel conductance, faster desensitization, and altered pharmacology. The B subunit is essential for modulating serotonergic signaling in neurons and enteric cells.