Signalling pathway associated with discharge of cnidocyst induced by reduced glutathione in Hydra plagiodesmica (Dioni, 1968)

Abstract

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 (Dioni, 1968) (Cnidaria: Hydrozoa). Once confirmed their stimulatory effect, we choose GSH to analyze the relevance of Ca2+, 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 Ca2+ via L-type voltage sensitive calcium channel (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 IP3 and Ca2+ as second messengers. Finally, we show that the genome of Hydra vulgaris (Pallas, 1766) predicts the existence of the different subunits of L-type VGCC, showing a high level of conservation when compared with other groups of Metazoa.