HTR6 (5-hydroxytryptamine receptor 6) is a G-protein coupled receptor that binds serotonin and mediates neurotransmitter signaling in the brain 1. Upon ligand binding, HTR6 undergoes conformational changes that activate downstream G(s) protein-coupled adenylate cyclase signaling 12. The receptor also functions as an mTOR signaling activator 3. HTR6 localizes to primary cilia through multiple targeting sequences in its intracellular loops and C-terminal tail, with ciliary accumulation facilitated by adaptor protein complex 1 (AP-1) and trafficking adapters TULP3 and RABL2 45. This subcellular localization is functionally significant, as ciliary HTR6 signaling affects cognition and brain development. Clinically, HTR6 has emerged as a key therapeutic target in psychiatric and neurological disorders. Genome-wide association studies identified HTR6 as a robustly linked gene to bipolar disorder via expression quantitative trait loci, representing a druggable target 6. HTR6 genetic polymorphisms show associations with male suicide risk in specific populations 7 and correlate with vestibular migraine onset 8. Additionally, HTR6 expression associates with breast cancer prognosis and immune microenvironment regulation 9, suggesting broader disease relevance beyond neuropsychiatric conditions.