Chapter 4 - Odor Sensing by Trace Amine-Associated Receptors

Abstract

Olfaction in vertebrates is primarily mediated by G-protein–coupled receptors (GPCRs), including odorant receptors (ORs) and trace amine-associated receptors (TAARs). Like ORs, TAARs are expressed in sparse olfactory sensory neurons (OSNs) via monoallelic receptor choice. Within OSNs, TAARs localize to both sensory cilia and axons that converge on stereotyped main olfactory bulb (MOB) glomeruli. Activated TAARs couple to canonical olfactory signaling proteins that transduce odor detection into neural activity. Many TAARs detect volatile amines including ethological odors derived from carnivores (2-phenylethylamine; TAAR4), male mice (trimethylamine; TAAR5), and carrion (cadaverine; TAAR13c). Some TAAR ligands are attractive or innately aversive, depending on the species. In mice, deletion of TAAR4 eliminates 2-phenylethylamine aversion, while deletion of TAAR5 eliminates trimethylamine attraction. TAARs provide an excellent model for mechanistic study of odor valence encoding.