Expression of Trace Amine-Associated Receptors in Human Nasal Mucosa

Trace amine-associated receptors (TAARs) have recently been identified in mouse olfactory epithelium (OE) and may be implicated in the detection of volatile amines, including pheromones. We investigated TAAR expression in human nasal mucosa, evaluating 32 nasal mucosa biopsies obtained from 16 patients with normal olfactory function undergoing routine nasal surgery. OE was identified on the basis of olfactory marker protein gene expression, and it was included in 11 samples out of 32. With the exception of TAAR1, which was detected at trace levels in a few samples of both groups, TAAR expression was limited to OE. TAAR5 was expressed in all OE samples at levels ranging from 15 to 1,480 copies/50 ng cDNA; TAAR8 was detected in 5 OE samples at trace levels and in another 5 OE samples at levels ranging from 11 to 33 cDNA copies/50 ng RNA; TAAR9, TAAR2, and TAAR5 were expressed at trace levels in 5, 3, and 3 OE samples, respectively. In conclusion, most TAARs, and particularly TAAR5, are selectively expressed in human OE. TAAR5 might play a significant functional role since it is known to be activated by trimethylamine, which is present in human secretions and has been implicated in behavioral responses.