Molecular cloning and functional characterization of the Aplysia FMRFamide-gated Na+ channel.
FMRFamide-gated Na+ channel (FaNaC) is the only known peptide-gated ion channel, which belongs to the epithelial Na+ channel/degenerin (ENaC/DEG) family. We have cloned a putative FaNaC from the Aplysia kurodai CNS library using PCR, and examined its characteristics in Xenopus oocytes. A. kurodai FaNaC (AkFaNaC) comprised with 653 amino acids, and the sequence predicts two putative membrane domains and a large extracellular domain as in other members of the ENaC/DEG family. In oocytes expressing AkFaNaC, FMRFamide evoked amiloride-sensitive Na+ current. Different from the known FaNaCs (Helix and Helisoma FaNaCs), AkFaNaC was blocked by external Ca2+ but not by Mg2+. Also, desensitization of the current was enhanced by Mg2+ but not by Ca2+. The FMRFamide-gated current was depressed in both low and high pH. These results indicate that AkFaNaC is an FaNaC of Aplysia, and that the channel has Aplysia specific functional domains.
Furukawa
Yasuo
Y
Laboratory of Neurobiology, Faculty of Integrated Arts and Sciences, Hiroshima University, Kagamiyama 1-7-1, Higashi-Hiroshima, 739-8521, Japan. yasfuru@hiroshima-u.ac.jp
Miyawaki
Yoshiyuki
Y
Abe
Genbu
G
D000584:Amiloride; D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia / Q000235:genetics / Q000502:physiology*; D002413:Cations, Divalent; D003001:Cloning, Molecular; D019835:FMRFamide / Q000502:physiology*; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics; D009865:Oocytes / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000235:genetics / Q000502:physiology*; D014981:Xenopus / Q000378:metabolism
D002413:Cations, Divalent; D015222:Sodium Channels; D019835:FMRFamide; D000584:Amiloride