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

J Biol Chem. 2010 Apr 16;285(16):11958-65. doi: 10.1074/jbc.M109.059998. Epub 2010 Feb 16.

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.

MeSH terms

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

Substances

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

Associated data

  • GENBANK/FN257513