Three homologous subunits form a high affinity peptide-gated ion channel in Hydra.

Abstract

Recently, three ion channel subunits of the degenerin (DEG)/epithelial Na(+) channel (ENaC) gene family have been cloned from the freshwater polyp Hydra magnipapillata, the Hydra Na(+) channels (HyNaCs) 2-4. Two of them, HyNaC2 and HyNaC3, co-assemble to form an ion channel that is gated by the neuropeptides Hydra-RFamides I and II. The HyNaC2/3 channel is so far the only cloned ionotropic receptor from cnidarians and, together with the related ionotropic receptor FMRFamide-activated Na(+) channel (FaNaC) from snails, the only known peptide-gated ionotropic receptor. The HyNaC2/3 channel has pore properties, like a low Na(+) selectivity and a low amiloride affinity, that are different from other channels of the DEG/ENaC gene family, suggesting that a component of the native Hydra channel might still be lacking. Here, we report the cloning of a new ion channel subunit from Hydra, HyNaC5. The new subunit is closely related to HyNaC2 and -3 and co-localizes with HyNaC2 and -3 to the base of the tentacles. Coexpression in Xenopus oocytes of HyNaC5 with HyNaC2 and -3 largely increases current amplitude after peptide stimulation and affinity of the channel to Hydra-RFamides I and II. Moreover, the HyNaC2/3/5 channel has altered pore properties and amiloride affinity, more similarly to other DEG/ENaC channels. Collectively, our results suggest that the three homologous subunits HyNaC2, -3, and -5 form a peptide-gated ion channel in Hydra that could contribute to fast synaptic transmission.

• Authors: Stefan Dürrnagel, Anne Kuhn, Charisios D Tsiairis, Michael Williamson, Hubert Kalbacher, Cornelis J P Grimmelikhuijzen, Thomas W Holstein, Stefan Gründer
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 285 Issue 16 Pg. 11958-65 (Apr 16 2010) ISSN: 1083-351X [Electronic] United States
• PMID: 20159980 (Publication Type: Journal Article)

Chemical References

• Degenerin Sodium Channels
• Epithelial Sodium Channels
• Ion Channels
• Nerve Tissue Proteins
• Protein Subunits
• Recombinant Proteins
• Sodium Channel Blockers
• Amiloride

Topics

• Amiloride (pharmacology)
• Amino Acid Sequence
• Animals
• Cloning, Molecular
• Degenerin Sodium Channels
• Epithelial Sodium Channels (chemistry, genetics, metabolism)
• Evolution, Molecular
• Feeding Behavior (drug effects, physiology)
• Female
• Hydra (genetics, metabolism, physiology)
• In Situ Hybridization
• In Vitro Techniques
• Ion Channel Gating
• Ion Channels (chemistry, genetics, metabolism)
• Molecular Sequence Data
• Nerve Tissue Proteins (chemistry, genetics, metabolism)
• Oocytes (metabolism)
• Protein Subunits
• Recombinant Proteins (chemistry, genetics, metabolism)
• Sequence Homology, Amino Acid
• Sodium Channel Blockers (pharmacology)
• Xenopus laevis