scholarly journals Functional expression of a pseudohypoaldosteronism type I mutated epithelial Na+ channel lacking the pore-forming region of its α subunit

1999 ◽  
Vol 104 (7) ◽  
pp. 967-974 ◽  
Author(s):  
Olivier Bonny ◽  
Ahmed Chraibi ◽  
Jan Loffing ◽  
Nicole Fowler Jaeger ◽  
Stefan Gründer ◽  
...  
Keyword(s):  
Functional Expression ◽  
Na Channel ◽  
Type I ◽  
Α Subunit ◽  
Epithelial Na Channel ◽  
Pseudohypoaldosteronism Type

scholarly journals On the Interaction between Amiloride and Its Putative α-Subunit Epithelial Na+Channel Binding Site

2005 ◽  
Vol 280 (28) ◽  
pp. 26206-26215 ◽  
Author(s):  
Ossama B. Kashlan ◽  
Shaohu Sheng ◽  
Thomas R. Kleyman
Keyword(s):  
Binding Site ◽  
Na Channel ◽  
Α Subunit ◽  
Epithelial Na Channel

Regulation of maturation and processing of ENaC subunits in the rat kidney

2006 ◽  
Vol 291 (3) ◽  
pp. F683-F693 ◽  
Author(s):  
Zuhal Ergonul ◽  
Gustavo Frindt ◽  
Lawrence G. Palmer
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Na Channel ◽  
Cortical Collecting Duct ◽  
Α Subunit ◽  
Salt Restriction ◽  
High K ◽  
Electrophysiological Measurements ◽  
Immature Form ◽  
Epithelial Na Channel

Antibodies directed against subunits of the epithelial Na channel (ENaC) were used together with electrophysiological measurements in the cortical collecting duct to investigate the processing of the proteins in rat kidney with changes in Na or K intake. When animals were maintained on a low-Na diet for 7–9 days, the abundance of two forms of the α-subunit, with apparent masses of 85 and 30 kDa, increased. Salt restriction also increased the abundance of the β-subunit and produced an endoglycosidase H (Endo H)-resistant pool of this subunit. The abundance of the 90-kDa form of the γ-subunit decreased, whereas that of a 70-kDa form increased and this peptide also exhibited Endo H-resistant glycosylation. These changes in α- and γ-subunits were correlated with increases in Na conductance elicited by a 4-h infusion with aldosterone. Changes in all three subunits were correlated with decreases in Na conductance when Na-deprived animals drank saline for 5 h. We conclude that ENaC subunits are mainly in an immature form in salt-replete rats. With Na depletion, the subunits mature in a process that involves proteolytic cleavage and further glycosylation. Similar changes occurred in α- and γ- but not β-subunits when animals were treated with exogenous aldosterone, and in β- and γ- but not α-subunits when animals were fed a high-K diet. Changes in the processing and maturation of the channels occur rapidly enough to be involved in the daily regulation of ENaC activity and Na reabsorption by the kidney.

Identification of a highly conserved sequence at the N-terminus of the epithelial Na + channel α subunit involved in gating

1999 ◽  
Vol 438 (5) ◽  
pp. 709-715 ◽  
Author(s):  
S. Gründer ◽  
N. Fowler Jaeger ◽  
I. Gautschi ◽  
L. Schild ◽  
B.C. Rossier
Keyword(s):  
Na Channel ◽  
Α Subunit ◽  
Conserved Sequence ◽  
N Terminus ◽  
Epithelial Na Channel

scholarly journals The Epithelial Na+Channel Is Inhibited by a Peptide Derived from Proteolytic Processing of Its α Subunit

2006 ◽  
Vol 281 (27) ◽  
pp. 18901-18907 ◽  
Author(s):  
Marcelo D. Carattino ◽  
Shaohu Sheng ◽  
James B. Bruns ◽  
Joseph M. Pilewski ◽  
Rebecca P. Hughey ◽  
...  
Keyword(s):  
Proteolytic Processing ◽  
Na Channel ◽  
Α Subunit ◽  
Epithelial Na Channel

Identification of a highly conserved sequence at the N-terminus of the epithelial Na+ channel α subunit involved in gating

1999 ◽  
Vol 438 (5) ◽  
pp. 709-715 ◽  
Author(s):  
S. Gründer ◽  
N. Fowler Jaeger ◽  
I. Gautschi ◽  
L. Schild ◽  
B.C. Rossier
Keyword(s):  
Na Channel ◽  
Α Subunit ◽  
Conserved Sequence ◽  
N Terminus ◽  
Epithelial Na Channel

Multiple epithelial Na+ channel domains participate in subunit assembly

2003 ◽  
Vol 285 (4) ◽  
pp. F600-F609 ◽  
Author(s):  
James B. Bruns ◽  
Baofeng Hu ◽  
Yoon J. Ahn ◽  
Shaohu Sheng ◽  
Rebecca P. Hughey ◽  
...  
Keyword(s):  
Transmembrane Protein ◽  
Expression System ◽  
Functional Expression ◽  
Full Length ◽  
Na Channel ◽  
Xenopus Laevis Oocyte ◽  
Subunit Interactions ◽  
Α Subunit ◽  
Hydrophobic Domain ◽  
Membrane Spanning

Epithelial sodium channels (ENaCs) are composed of three structurally related subunits that form a tetrameric channel. The Xenopus laevis oocyte expression system was used to identify regions within the ENaC α-subunit that confer a dominant negative phenotype on functional expression of αβγ-ENaC to define domains that have a role in subunit-subunit interactions. Coexpression of full-length mouse αβγ-ENaC with either 1) the α-subunit first membrane-spanning domain and short downstream hydrophobic domain (α-M1H1); 2) α-M1H1 and its downstream hydrophilic extracellular loop (α-M1H1-ECL); 3) the membrane-spanning domain of a control type 2 transmembrane protein (glutamyl transpeptidase; γ-GT) fused to the α-ECL (γ-GT-α-ECL); 4) the extracellular domain of a control type 1 transmembrane protein (Tac) fused to the α-subunit second membrane-spanning domain and short upstream hydrophobic domain (Tac-α-H2M2); or 5) the α-subunit cytoplasmic COOH terminus (α-Ct) significantly reduced amiloride-sensitive Na+ currents in X. laevis oocytes. Functional expression of Na+ channels was not inhibited when full-length αβγ-ENaC was coexpressed with either 1) the α-ECL lacking a signal-anchor sequence, 2) α-M1H1 and α-Ct expressed as a fusion protein, 3) full-length γ-GT, or 4) full-length Tac. Furthermore, the expression of ROMK channels was not inhibited when full-length ROMK was coexpressed with either α-M1H1-ECL or α-Ct. Full-length FLAG-tagged α-, β-, or γ-ENaC coimmunoprecipitated with myc-tagged α-M1H1-ECL, whereas wild-type γ-GT did not. These data suggest that multiple sites within the α-subunit participate in subunit-subunit interactions that are required for proper assembly of the heterooligomeric ENaC complex.

scholarly journals Identification of an Amiloride Binding Domain within the α-Subunit of the Epithelial Na+Channel

1997 ◽  
Vol 272 (34) ◽  
pp. 21075-21083 ◽  
Author(s):  
Iskander I. Ismailov ◽  
Thomas Kieber-Emmons ◽  
Chaomei Lin ◽  
Bakhram K. Berdiev ◽  
Vadim Gh. Shlyonsky ◽  
...  
Keyword(s):  
Binding Domain ◽  
Na Channel ◽  
Α Subunit ◽  
Epithelial Na Channel

Location and function of the epithelial Na channel in the cochlea

2001 ◽  
Vol 280 (2) ◽  
pp. F214-F222 ◽  
Author(s):  
Vincent Couloigner ◽  
Michel Fay ◽  
Sabri Djelidi ◽  
Nicolette Farman ◽  
Brigitte Escoubet ◽  
...  
Keyword(s):  
Stria Vascularis ◽  
Spiral Ganglion ◽  
Endocochlear Potential ◽  
Na Channel ◽  
Spiral Ligament ◽  
Α Subunit ◽  
Subunit Mrna ◽  
Spiral Limbus ◽  
Epithelial Na Channel

In the cochlea, endolymph is a K-rich and Na-poor fluid. The purpose of the present study was to check the presence and to assess the role of epithelial Na channel (ENaC) in this organ. α-, β-, and γ-ENaC subunit mRNA, and proteins were detected in rat cochlea by RT-PCR and Western blot. α-ENaC subunit mRNA was localized by in situ hybridization in both epithelial (stria vascularis, spiral prominence, spiral limbus) and nonepithelial structures (spiral ligament, spiral ganglion). The α-ENaC-positive tissues were also positive for β-subunit mRNA (except spiral ganglion) or for γ-subunit mRNA (spiral limbus, spiral ligament, and spiral ganglion), but the signals of β- and γ-subunits were weaker than those observed for α-subunit. In vivo, the endocochlear potential was recorded in guinea pigs under normoxic and hypoxic conditions after endolymphatic perfusion of ENaC inhibitors (amiloride, benzamil) dissolved either in K-rich or Na-rich solutions. ENaC inhibitors altered the endocochlear potential when Na-rich but not when K-rich solutions were perfused. In conclusion, ENaC subunits are expressed in epithelial and nonepithelial cochlear structures. One of its functions is probably to maintain the low concentration of Na in endolymph.

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