Peptide inhibition of ENaC.
Liddle's disease is an autosomal dominant form of human hypertension resulting from a basal activation of amiloride-sensitive Na+ channels (ENaC). This channel activation is produced by mutations in the beta- and/or gamma-carboxy-terminal cytoplasmic tails, in many cases causing a truncation of the last 45-76 amino acids. In this study, we tested two hypotheses; first, beta- and gamma-ENaC C-terminal truncation mutants (beta DeltaC and gamma DeltaC), in combination with the wild-type alpha-ENaC subunit, reproduce the Liddle's phenotype at the single channel level, i.e., an increase in open probability (Po), and second, these C-terminal regions of beta- and gamma-ENaC act as intrinsic blockers of this channel. Our results indicate that alpha beta DeltaC gamma DeltaC-rENaC, incorporated into planar lipid bilayers, has a significantly higher single channel Po compared to the wild-type channel (0.85 vs 0.60, respectively), and that 30-mer synthetic peptides corresponding to the C-terminal region of either beta- or gamma-ENaC block the basal-activated channel in a concentration-dependent fashion. Moreover, there was a synergy between the peptides for channel inhibition when added together. We conclude that the increase in macroscopic Na+ reabsorption that occurs in Liddle's disease is at least in part due to an increase in single channel Po and that the cytoplasmic tails of the beta- and gamma-ENaC subunits are important in the modulation of ENaC activity.
Ismailov
I I
II
Department of Physiology and Biophysics, University of Alabama at Birminghama 35294-0005, USA.
Shlyonsky
V G
VG
Serpersu
E H
EH
Fuller
C M
CM
Cheung
H C
HC
Muccio
D
D
Berdiev
B K
BK
Benos
D J
DJ
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D053503:Epithelial Sodium Channels; D008051:Lipid Bilayers / Q000378:metabolism; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010455:Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism; D012996:Solutions
D053503:Epithelial Sodium Channels; D008051:Lipid Bilayers; D010446:Peptide Fragments; D010455:Peptides; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D012996:Solutions