The epithelial sodium channel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes

Dipnoi)

Minoru Uchiyama*, Sho Maejima, Sumio Yoshie, Yoshihiro Kubo, Norifumi Konno, Jean M P Joss

*Corresponding author for this work

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Epithelial sodium channel (ENaC) is a Na+-selective, aldosterone-stimulated ion channel involved in sodium transport homeostasis. ENaC is rate-limiting for Na+ absorption in the epithelia of osmoregulatory organs of tetrapods. Although the ENaC/degenerin gene family is proposed to be present in metazoans, no orthologues or paralogues for ENaC have been found in the genome databases of teleosts. We studied full-length cDNA cloning and tissue distributions of ENaCα, β and γ subunits in the Australian lungfish, Neoceratodus forsteri, which is the closest living relative of tetrapods. Neoceratodus ENaC (nENaC) comprised three subunits: nENaCα, β and γ proteins. The nENaCα, β and γ subunits are closely related to amphibian ENaCα, β and γ subunits, respectively. Three ENaC subunit mRNAs were highly expressed in the gills, kidney and rectum. Amiloride-sensitive sodium current was recorded from Xenopus oocytes injected with the nENaCαβγ subunit complementary RNAs under a two-electrode voltage clamp. nENaCα immunoreactivity was observed in the apical cell membrane of the gills, kidney and rectum. Thus, nENaC may play a role in regulating sodium transport of the lungfish, which has a renin-angiotensin-aldosterone system. This is interesting because there may have been an ENaC sodium absorption system controlled by aldosterone before the conquest of land by vertebrates.

Original languageEnglish
Pages (from-to)4795-4802
Number of pages8
JournalProceedings of the Royal Society B: Biological Sciences
Volume279
Issue number1748
DOIs
Publication statusPublished - 2012

Keywords

  • Dipnoi
  • Evolution of ion channel
  • Immunoreactivity
  • Sodium transport
  • Xenopus oocyte

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