Meeting Abstract
Ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels, characterized for their role in synaptic communication in vertebrate nervous systems, and also implicated in the chemosensory and olfaction of insects. Here we examined the hypothesis that an iGluR lineage has evolved in cnidarians with a role in the innate immune pathways. By 2D-gel electrophoresis profiling in tandem with Mass Spectrometry, it was determined that the symbiotic model cnidarian, Exaiptasia pallida, increases the protein levels of an iGluR (EpiGluR) homolog during the response to exposure of the infectious bacterial agent Vibrio coralliilyticus. Bioinformatic analyses support the identity of this gene as an iGluR. Phylogenetic analyses, using the full coding gene, indicate the EpiGluR ligand-binding domain is not specific to classical synaptic-involved NMDA, kainate, or AMPA ligands and phylogenetically branches out of the insect antennal ionotropic receptors (IR) clade. This supports the hypothesis that the cnidarian EpiGluR belongs to a separate evolutionary lineage within the phylogeny of iGluRs, and has retained molecular characteristics to respond to chemical stimuli. In plants, iGluR homologs have been implicated in sensing molecular patterns, such as pathogen- and damage-associated molecular patterns (PAMPs, DAMPs) that act together in order for a host to differentiate between pathologically damaging microbes and beneficial or harmless microbes. Based on this, we postulate that iGluRs may mediate the PAMP-triggered immunity via calcium channels by pattern-recognition particles. These findings provide the beginnings of a foundation for further functional analysis of these receptors to better comprehend the role of EpiGluR and its ligand-specificity within cnidarian immunity.
