Signalling Pathway Associated to Discharge of Cnidocyst Induced by Reduced Glutathione in Hydra

In the present work we study the effect of different stimuli (living preys, its homogenate, and reduced glutathione (GSH)) on the discharge of desmonemes in the freshwater cnidarian, Hydra plagiodesmica . Once confirmed their stimulatory effect, we choose GSH in order to analyse the relevance of Ca 2+ , the probable identity of the sensory receptor molecule, and the specific signalling pathway driving the discharge mechanism. Our results show that not only mechanical, but also chemical stimuli by itself may stimulate the discharge of desmonemes. Using calcium chelators, we verify that the discharge mechanism triggered by GSH, is dependent on calcium. By mean of drugs that inhibit proteins pertaining to canonical signalling pathways, including GPCRs, we show that GSH causes the influx of Ca 2+ via L-type VGCC, and its release by mean of endoplasmic reticulum calcium channels. Moreover, our results suggest that the putative receptor for GSH is a GPCR coupled to Gq, which produces IP 3 and Ca 2+ as second messengers. Finally, we show that the genome of Hydra predicts the existence of the different subunits of L-type VGCC, showing a high level of conservation when compared with other groups of Metazoa.