Trace amine-associated receptor 5 is a protein that in humans is encoded by the TAAR5 gene.[5][6][7] In vertebrates, TAAR5 is expressed in the olfactory epithelium.[8]
Human TAAR5 (hTAAR5) is a functional trace amine-associated receptor which acts as an olfactory receptor for tertiary amines.[8][9] Trimethylamine and N,N-dimethylethylamine are full agonists of hTAAR5.[9][10][11] The amber-woody fragrance timberol antagonizes this activity of trimethylamine.[12] 3-Iodothyronamine is an inverse agonist of hTAAR5.[13][14] Recent studies highlighted the significant role of TAAR5 in the central nervous system and periphery. Beta-galactosidase mapping of TAAR5 expression showed its localization not only in the glomeruli but also in deeper layers of olfactory bulb projecting to the limbic brain olfactory circuitry. Moreover, TAAR5 knockout mice show increased adult neurogenesis and elevated number of dopamine neurons. Also, it was observed statistically significant changes in osmotic erythrocyte fragility in TAAR5-KO mice.[15]
Mutations in the TAAR5 gene were found to affect human olfaction. Icelanders with a mutation in the gene were less likely to describe fish smell containing trimethylamine as unpleasant, and described licorice odor and cinnamon odor more intensely.[16]
All TAARs except TAAR1 function as olfactory receptors, based on studies in rodent, primate, and fish [4,7,10]. TAAR expression is highly enriched in the olfactory system by quantitative PCR (qPCR) analysis, with little or no expression in other tissues examined [4].
We show that [human TAAR5] responds to the tertiary amine N,N-dimethylethylamine and to a lesser extent to trimethylamine, a structurally related agonist for mouse and rat TAAR5 (Liberles and Buck, 2006; Staubert et al., 2010; Ferrero et al., 2012).
While mice produce gender-specific amounts of urinary TMA levels and were attracted by TMA, this odor is repellent to rats and aversive to humans [19], indicating that there must be species-specific functions. ... Furthermore, a homozygous knockout of murine TAAR5 abolished the attraction behavior to TMA [19]. Thus, it is concluded that TAAR5 itself is sufficient to mediate a behavioral response at least in mice. ... Whether the TAAR5 activation by TMA elicits specific behavioral output like avoidance behavior in humans still needs to be examined.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.
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TAAR1 |
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TAAR2 |
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TAAR5 |
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† References for all endogenous human TAAR1 ligands are provided at List of trace amines
‡ References for synthetic TAAR1 agonists can be found at TAAR1 or in the associated compound articles. For TAAR2 and TAAR5 agonists and inverse agonists, see TAAR for references.
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