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Papers of the Week


Papers: 21 Sep 2019 - 27 Sep 2019


Animal Studies


2019 Nov 11


Philos Trans R Soc Lond B Biol Sci


374


1785

Drosophila menthol sensitivity and the Precambrian origins of transient receptor potential-dependent chemosensation.

Authors

Himmel NJ, Letcher JM, Sakurai A, Gray TR, Benson MN, Cox DN
Philos Trans R Soc Lond B Biol Sci. 2019 Nov 11; 374(1785):20190369.
PMID: 31544603.

Abstract

Transient receptor potential (TRP) cation channels are highly conserved, polymodal sensors which respond to a wide variety of stimuli. Perhaps most notably, TRP channels serve critical functions in nociception and pain. A growing body of evidence suggests that transient receptor potential melastatin (TRPM) and transient receptor potential ankyrin (TRPA) thermal and electrophile sensitivities predate the protostome-deuterostome split (greater than 550 Ma). However, TRPM and TRPA channels are also thought to detect modified terpenes (e.g. menthol). Although terpenoids like menthol are thought to be aversive and/or harmful to insects, mechanistic sensitivity studies have been largely restricted to chordates. Furthermore, it is unknown if TRP-menthol sensing is as ancient as thermal and/or electrophile sensitivity. Combining genetic, optical, electrophysiological, behavioural and phylogenetic approaches, we tested the hypothesis that insect TRP channels play a conserved role in menthol sensing. We found that topical application of menthol to larvae elicits a – and -dependent nocifensive rolling behaviour, which requires activation of Class IV nociceptor neurons. Further, in characterizing the evolution of TRP channels, we put forth the hypotheses that three previously undescribed TRPM channel clades (basal, αTRPM and βTRPM), as well as TRPs with residues critical for menthol sensing, were present in ancestral bilaterians. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.