Cloning and functional expression of a novel degenerin-like Na+ channel gene in mammals.
1. A degenerate polymerase chain reaction (PCR) homology screening procedure was applied to rat brain cDNA in order to identify novel genes belonging to the amiloride-sensitive Na+ channel and degenerin (NaC/DEG) family of ion channels. A single gene was identified that encodes a protein related to but clearly different from the already cloned members of the family (18-30 % amino acid sequence identity). Phylogenetic analysis linked this protein to the group of ligand-gated channels that includes the mammalian acid-sensing ion channels and the Phe-Met-Arg-Phe-amide (FMRFamide)-activated Na+ channel. 2. Expression of gain-of-function mutants after cRNA injection into Xenopus laevis oocytes or transient transfection of COS cells induced large constitutive currents. The activated channel was amiloride sensitive (IC50, 1.31 microM) and displayed a low conductance (9-10 pS) and a high selectivity for Na+ over K+ (ratio of the respective permeabilities, PNa+/PK+ >= 10), all of which are characteristic of NaC/DEG channel behaviour. 3. Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed a predominant expression of its mRNA in the small intestine, the liver (including hepatocytes) and the brain. This channel has been called the brain-liver-intestine amiloride-sensitive Na+ channel (BLINaC). 4. Corresponding gain-of-function mutations in Caenorhabditis elegans degenerins are responsible for inherited neurodegeneration in the nematode. Besides the BLINaC physiological function that remains to be established, mutations in this novel mammalian degenerin-like channel might be of pathophysiological importance in inherited neurodegeneration and liver or intestinal pathologies.
Sakai
H
H
Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UPR 411, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France.
Lingueglia
E
E
Champigny
G
G
Mattei
M G
MG
Lazdunski
M
M
D062565:Acid Sensing Ion Channels; D000595:Amino Acid Sequence; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D015152:Blotting, Northern; D019556:COS Cells; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D062626:Degenerin Sodium Channels; D053503:Epithelial Sodium Channels; D017404:In Situ Hybridization, Fluorescence; D007473:Ion Channels / Q000096:biosynthesis* / Q000235:genetics; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015222:Sodium Channels / Q000096:biosynthesis* / Q000235:genetics*; D014018:Tissue Distribution; D014981:Xenopus
D062565:Acid Sensing Ion Channels; C568425:Asic2 protein, rat; D062626:Degenerin Sodium Channels; D053503:Epithelial Sodium Channels; D007473:Ion Channels; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D015222:Sodium Channels