TRPA is a family of
transient receptor potentialion channels. The TRPA family is made up of 7 subfamilies: TRPA1, TRPA- or TRPA1-like, TRPA5, painless, pyrexia, waterwitch, and HsTRPA. TRPA1 is the only subfamily widely expressed across animals, while the other subfamilies (collectively referred to as the basal clade) are largely absent in
deuterostomes (and in the case of HsTRPA, only expressed in
hymenopteran insects).[2][1][3][4]
TRPA1s have been the most extensively studied subfamily; they typically contain 14 N-terminal
ankyrin repeats and are believed to function as mechanical stress, temperature, and chemical sensors. TRPA1 is known to be activated by compounds such as
isothiocyanate (which are the pungent chemicals in substances such as
mustard oil and
wasabi) and
Michael acceptors (e.g.
cinnamaldehyde). These compounds are capable of forming covalent chemical bonds with the protein's
cysteins.[5] Non-covalent activators of TRPA1 also exists, such as
methyl salicylate,
menthol, and the synthetic compound
PF-4840154.[6][1][7]
The thermal sensitivity of TRPAs varies by species. For example, TRPA1 functions as a high-temperature sensor in insects and snakes, but as a cold sensor in mammals.[8] The basal TRPAs have evolved some degree of thermal sensitivity as well: painless and pyrexia function in high-temperature sensing in
Drosophila melanogaster, and the honey bee HsTRPA underwent
neofunctionalization following its divergence from waterwitch, gaining function as a high-temperature sensor.[9]
TRPA1s promiscuity with respect to sensory modality has been the source of controversy, particularly when considering its ability to detect cold.[10] More recent work has alternatively (or additionally) proposed that
reactive oxygen species activate TRPA1, across species.[11][12]
^
abPeng G, Shi X, Kadowaki T (March 2015). "Evolution of TRP channels inferred by their classification in diverse animal species". Molecular Phylogenetics and Evolution. 84: 145–57.
doi:
10.1016/j.ympev.2014.06.016.
PMID24981559.
^Panzano VC, Kang K, Garrity PA (June 2010). "Infrared snake eyes: TRPA1 and the thermal sensitivity of the snake pit organ". Science Signaling. 3 (127): pe22.
doi:
10.1126/scisignal.3127pe22.
PMID20571127.
S2CID13504270.