Broad Sensitivity of Drosophila Melanogaster TRPA1 to Noxious Chemicals

Abstract

The TRPA1 ion channel functions as a broadly-tuned chemonociceptor in many species. In the fruit fly, Drosophila melanogaster, dTRPA1(A) is known to contribute to chemosensation for its expression in a subset of gustatory receptor neurons in the labral sense organ and in the labellum. These neurons also express a gustatory receptor Gr66a and mediate the avoidance of non-volatile compounds that are recognized by mammalian bitter taste receptors. In this study we aimed to further characterize the chemosensory properties of dTRPA1(A). This channel was reported to mediate the aversion towards citronellal, but to be activated indirectly through a G protein/PLC signalling cascade. We expressed the TRPA1(A) in a mammalian heterologous expression system. By use of the whole cell patch clamp technique, we were able to show that Citronellal activates TRPA1(A) in HEK293T cells. It has been recently shown that TRPA1 plays a role in the acute mammalian nocifensive responses to bacterial lipopolysaccharides (LPS). We hypothesized that dTRPA1 endows Drosophila fruit flies with the ability to detect LPS and to adopt avoiding behaviours towards this compound. Behavioural experiments showed that D. melanogaster flies avoid laying eggs on food contaminated with bacteria through mechanisms that are partly dependent on dTRPA1 activation. By use of the whole cell patch clamp technique we could illustrate the activation of dTRPA1(A) currents in HEK293T cells. Altogether, these experiments indicate for a direct role of TRPA1 in the detection and avoidance of a wide variety of noxious chemicals in D. melanogaster.