Prof. Stefan Gründer, University Hospital Aachen, Germany
Professor Stefan Günder from the Insitute of Physiology at the University Hospital Aachen will present: "Peptide-gated ion channels of Hydra: stoichiometry and ligand-binding site"
To shed light on the evolution of synaptic transmission and neurotransmitters, the Gründer lab comprehensively analyzed DEG/ENaC ion channels, the Hydra Na+ channels (HyNaCs), in the freshwater polyp Hydra. They identified the rules under which 10 HyNaCs assemble into heterotrimers and demonstrated that they are directly gated by neuropeptides of the Hydra nervous system, the Hydra-RFamides, with high affinity. HyNaC-expressing cells localize to the base of the tentacles and the foot region, adjacent to peptide-expressing neurons, suggesting that Hydra-RFamides are the natural ligands of HyNaCs. HyNaCs are likely expressed in epitheliomuscular cells and are thus potentially involved in neuromuscular transmission. Behavioral analysis in live animals indeed showed that HyNaC blockers delay tentacle movement. Collectively, these results suggest that Hydra co-opted neuropeptides for neuromuscular transmission. Most recent findings revealed the stoichiometry of these heterotrimeric channels and identified a putative ligand-binding site at one subunit-subunit-interface, suggesting that peptide-binding sites evolved independently at least twice in this ion channel family.