Functional Analysis of Ligand-Gated Chloride Channels in a Cnidarian Sheds Light on the Evolution of Inhibitory Signaling.

Rs of the cnidarian radiation and find that none is activated by GABA or glycine, whereas three are activated by glutamate. Using site-directed mutagenesis, we identify a lysine residue in the canonical ligand-binding pocket that is important for activation by glutamate. Our results identify a group of inhibitory ion channel receptors in Cnidaria that use glutamate as a ligand. Moreover, they suggest that inhibitory ion channel receptors in Cnidaria massively diversified, which may have been instrumental in the evolution of complex behaviors and sensory processing by the cnidarian nervous system.