Otopetrin family

The otopetrin family is a group of proteins that were first identified based on their essential role in the vestibular system, and were later shown to be expressed in many different tissues, including taste receptor cells.[1] They are named after the Greek word "o̱tós," which means ear and "pétrā," which means rock, in reference to their role in the formation of otoconia/otoliths in the inner ear. The secondary structure of otopetrin-1 (OTOP1) is predicted to include 12 transmembrane domains, with three conserved sub-domains (OD-1 to OD-III).[2] Otopetrins were initially thought to modulate calcium homeostasis and influx of calcium in response to extracellular ATP[3] but were subsequently shown to form proton-selective ion channels.[1]

The otopetrins are required for normal formation of otoconia/otoliths in the inner ear. Otoconia are minute biomineral particles embedded in a gelatinous membrane that overlies the sensory epithelium in the inner ear. Gravity and acceleration cause the octoconia to deflect the stereocilia of sensory hair cells. Otoconia are required for normal processing of information regarding spatial orientation and acceleration.[3][4][5]

Otopetrin-1 was recently found to be an essential sour taste receptor,[6] by its interaction with KIR.[7]