title: Second transmembrane domain modulates epithelial sodium channel gating in response to shear stress.
abstract: Na(+) absorption and K(+) secretion in the distal segments of the nephron are modulated by the tubular flow rate. Epithelial Na(+) channels (ENaC), composed of α-, β-, and γ-subunits respond to laminar shear stress (LSS) with an increase in open probability. Higher vertebrates express a δ-ENaC subunit that is functionally related to the α-subunit, while sharing only 35% of sequence identity. We investigated the response of δβγ channels to LSS. Both the time course and magnitude of activation of δβγ channels by LSS were remarkably different from those of αβγ channels. ENaC subunits have similar topology, with an extracellular region connected by two transmembrane domains with intracellular N and C termini. To identify the specific domains that are responsible for the differences in the response to flow of αβγ and δβγ channels, we generated a series of α-δ chimeras and site-specific α-subunit mutants and examined parameters of activation by LSS. We found that specific sites in the region encompassing and just preceding the second transmembrane domain were responsible for the differences in the magnitude and time course of channel activation by LSS.
authors.affiliation: Renal-Electrolyte Div., Dept. of Medicine, Pittsburgh, PA 15261, USA.
authors.forename: Tania
authors.initials: T
authors.lastname: Abi-Antoun
authors.forename: Shujie
authors.initials: S
authors.lastname: Shi
authors.forename: Lindsey A
authors.initials: LA
authors.lastname: Tolino
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Kleyman
authors.forename: Marcelo D
authors.initials: MD
authors.lastname: Carattino
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004305:Dose-Response Relationship, Drug; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating; D040542:Mechanotransduction, Cellular; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009865:Oocytes; D017434:Protein Structure, Tertiary; D012964:Sodium / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013314:Stress, Mechanical; D013329:Structure-Activity Relationship; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; C507045:SCNN1A protein, human; C507048:SCNN1B protein, human; C507051:SCNN1D protein, human; C507052:SCNN1G protein, human; D026941:Sodium Channel Blockers; D012964:Sodium