scholarly journals 5′ Heterogeneity in epithelial sodium channel α-subunit mRNA leads to distinct NH2-terminal variant proteins

1998 ◽  
Vol 274 (5) ◽  
pp. C1312-C1323 ◽  
Author(s):  
Christie P. Thomas ◽  
Scott Auerbach ◽  
John B. Stokes ◽  
Kenneth A. Volk
Keyword(s):  
Sodium Channel ◽  
Xenopus Oocytes ◽  
Epithelial Sodium Channel ◽  
Open Reading Frame ◽  
Splice Sites ◽  
Α Subunit ◽  
Exon 2 ◽  
Reading Frame ◽  
Subunit Mrna ◽  
Epithelial Sodium Channel Enac

The amiloride-sensitive epithelial sodium channel (ENaC) is composed of three subunits: α, β, and γ. The human α-ENaC subunit is expressed as at least two transcripts (N. Voilley, E. Lingueglia, G. Champigny, M. G. Mattei, R. Waldmann, M. Lazdunski, and P. Barbry. Proc. Natl. Acad. Sci. USA91: 247–251, 1994). To determine the origin of these transcripts, we characterized the 5′ end of the α-ENaC gene. Four transcripts that differ at their first exon were identified. Exon 1A splices to exon 2 to form the 5′ end of α-ENaC1, whereas exon 1B arises separately and continues into exon 2 to form α-ENaC2. Other variant mRNAs, α-ENaC3 and α-ENaC4, are formed by activating 5′ splice sites within exon 1B. Although α-ENaC3 and -4 did not change the open reading frame for α-ENaC, α-ENaC2 contains upstream ATGs that add 59 amino acids to the previous (α-ENaC1) protein. To address the significance of these isoforms, both proteins were expressed in Xenopus oocytes. The cRNA for each α-ENaC transcript when combined with β- and γ-ENaC cRNA reconstituted a low-conductance ion channel with amiloride-sensitive currents of similar characteristics. We have thus identified variant α-ENaC mRNAs that lead to functional ENaC peptides.

Differential Regulation of the Epithelial Sodium Channel (ENaC) in Rat Kidney, Lung and Distal Colon in Response to Aldosterone.

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 724-724
Author(s):  
Shyama M E Masilamani ◽  
Gheun-Ho Kim ◽  
Mark A Knepper
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Distal Colon ◽  
Β Subunit ◽  
Dietary Salt ◽  
Α Subunit ◽  
Salt Restriction ◽  
Γ Subunit ◽  
Dietary Salt Restriction ◽  
Epithelial Sodium Channel Enac

P170 The mineralocorticoid hormone, aldosterone increases renal tubule Na absorption via increases in the protein abundances of the α-subunit of the epithelial sodium channel (ENaC) and the 70 kDa form of the γ- subunit of ENaC (JCI 104:R19-R23). This study assesses the affect of dietary salt restriction on the regulation of the epithelial sodium channel (ENaC) in the lung and distal colon, in addition to kidney, using semiquantitative immunoblotting. Rats were placed initially on either a control Na intake (0.02 meq/day), or a low Na intake (0.2 meq/day) for 10 days. The low salt treated rats demonstrated an increase in plasma aldosterone levels at day 10 (control = 0.78 + 0.32 nM; Na restricted = 3.50 + 1.30 nM). In kidney homogenates, there were marked increases in the band density of the α-subunit of ENaC (286 % of control) and the 70 kDa form of γ-subunit of ENaC (262 % of control), but no increase in the abundance of the β-subunit of ENaC. In lung homogenates, there was no significant change in the band densities of the α, β, or γ subunits of ENaC. In distal colon, there was an increase in the band density of the β-subunit of ENaC (311 % of control) and an increase in both the 85 kDa (2355% of control) and 70 kDa (843 % of control) form of the γ subunit of ENaC in response to dietary Na restriction. However, there was no significant difference in the band density of the α-subunit of ENaC. These findings demonstrate tissue specific regulation of the three subunits of ENaC in response to dietary salt restriction.

Downregulation of Epithelial Sodium Channel (ENaC) by CFTR Co-expressed in Xenopus Oocytes is Independent of Cl − Conductance

1999 ◽  
Vol 169 (3) ◽  
pp. 175-188 ◽  
Author(s):  
H. Chabot ◽  
M.F. Vives ◽  
A. Dagenais ◽  
Cz. Grygorczyk ◽  
Y. Berthiaume ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Xenopus Oocytes ◽  
Epithelial Sodium Channel ◽  
Cl Conductance ◽  
Epithelial Sodium Channel Enac

scholarly journals Protease Modulation of the Activity of the Epithelial Sodium Channel Expressed in Xenopus Oocytes

1998 ◽  
Vol 111 (1) ◽  
pp. 127-138 ◽  
Author(s):  
Ahmed Chraïbi ◽  
Véronique Vallet ◽  
Dmitri Firsov ◽  
Solange Kharoubi Hess ◽  
Jean-Daniel Horisberger
Keyword(s):  
Sodium Channel ◽  
Xenopus Oocytes ◽  
Epithelial Sodium Channel ◽  
Cell Surface Expression ◽  
K Channel ◽  
Na Channel ◽  
Extracellular Proteases ◽  
Open Probability ◽  
Α Subunit ◽  
Channel Protein

We have investigated the effect of extracellular proteases on the amiloride-sensitive Na+ current (INa) in Xenopus oocytes expressing the three subunits α, β, and γ of the rat or Xenopus epithelial Na+ channel (ENaC). Low concentrations of trypsin (2 μg/ml) induced a large increase of INa within a few minutes, an effect that was fully prevented by soybean trypsin inhibitor, but not by amiloride. A similar effect was observed with chymotrypsin, but not with kallikrein. The trypsin-induced increase of INa was observed with Xenopus and rat ENaC, and was very large (∼20-fold) with the channel obtained by coexpression of the α subunit of Xenopus ENaC with the β and γ subunits of rat ENaC. The effect of trypsin was selective for ENaC, as shown by the absence of effect on the current due to expression of the K+ channel ROMK2. The effect of trypsin was not prevented by intracellular injection of EGTA nor by pretreatment with GTP-γS, suggesting that this effect was not mediated by G proteins. Measurement of the channel protein expression at the oocyte surface by antibody binding to a FLAG epitope showed that the effect of trypsin was not accompanied by an increase in the channel protein density, indicating that proteolysis modified the activity of the channel present at the oocyte surface rather than the cell surface expression. At the single channel level, in the cell-attached mode, more active channels were observed in the patch when trypsin was present in the pipette, while no change in channel activity could be detected when trypsin was added to the bath solution around the patch pipette. We conclude that extracellular proteases are able to increase the open probability of the epithelial sodium channel by an effect that does not occur through activation of a G protein-coupled receptor, but rather through proteolysis of a protein that is either a constitutive part of the channel itself or closely associated with it.

Revealing a subclinical salt-losing phenotype in heterozygous carriers of the novel S562P mutation in the α subunit of the epithelial sodium channel

2009 ◽  
Vol 70 (2) ◽  
pp. 252-258 ◽  
Author(s):  
Felix G. Riepe ◽  
Miguel X. P. Van Bemmelen ◽  
Francois Cachat ◽  
Hansjörg Plendl ◽  
Ivan Gautschi ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
The Novel ◽  
Α Subunit ◽  
Heterozygous Carriers

scholarly journals Ankyrin G Expression Regulates Apical Delivery of the Epithelial Sodium Channel (ENaC)

2016 ◽  
Vol 292 (1) ◽  
pp. 375-385 ◽  
Author(s):  
Christine A. Klemens ◽  
Robert S. Edinger ◽  
Lindsay Kightlinger ◽  
Xiaoning Liu ◽  
Michael B. Butterworth
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Ankyrin G ◽  
Epithelial Sodium Channel Enac

The epithelial sodium channel (ENaC) is intracellularly located as a tetramer

2002 ◽  
Vol 444 (4) ◽  
pp. 549-555 ◽  
Author(s):  
Lisette Dijkink ◽  
Anita Hartog ◽  
René Bindels ◽  
Carel van Os
Keyword(s):  
Sodium Channel ◽  
Epithelial Sodium Channel ◽  
Epithelial Sodium Channel Enac

Coding sequence and expression of the homeobox gene Hox 1.3

Development ◽  
1988 ◽  
Vol 102 (2) ◽  
pp. 349-359 ◽  
Author(s):  
M. Fibi ◽  
B. Zink ◽  
M. Kessel ◽  
A.M. Colberg-Poley ◽  
S. Labeit ◽  
...  
Keyword(s):  
Homeobox Gene ◽  
Cell System ◽  
T Antigen ◽  
Open Reading Frame ◽  
Homeodomain Protein ◽  
Chromosome 11 ◽  
3T3 Cells ◽  
Exon 2 ◽  
Reading Frame ◽  
3T3 Fibroblasts

We have characterized Hox 1.3 (previously described as m2), a murine homeobox-containing gene, which is a member of the Hox 1 cluster located on chromosome 6. A cloned cDNA was isolated from an Okayama-Berg library generated from the chemically transformed cell line MB66 MCA ACL6. The protein sequence of 270 amino acids was deduced from the nucleotide sequence of an open reading frame containing the homeobox. The open reading frame is interrupted at the genomic level by a 960 bp intron and is organized in two exons. The Hox 1.3 protein was found to contain extensive sequence homology with the murine homeodomain protein Hox 2.1, which is encoded on chromosome 11. There are two homology with the regions in the first exon, i.e. a hexapeptide conserved in many homeobox-containing genes and the N-terminal domain, which was found to be homologous only to Hox 2.1. Furthermore, in exon 2 the homologies of the homeodomain regions are extended up to the carboxy terminus of Hox 1.3 and Hox 2.1. During prenatal murine development, maximal expression of Hox 1.3 is observed in 12-day embryonic tissue. The two transcripts carrying the Hox 1.3 homeobox are 1.9 kb and about 4 kb in length. An abundant Hox 1.3-specific 1.9 kb RNA is also found in F9 cells which were induced for parietal endoderm differentiation, whereas F9 teratocarcinoma stem cells do not stably express this specific RNA. Induction of the transcript occurs immediately after retinoic acid/cAMP treatment and the RNA level remains high for 5 days. Thus, the kinetics are different from the previously described homeobox transcripts Hox 1.1 and Hox 3.1. Interestingly, by analogy to the F9 cell system a negative correlation between transformation and Hox 1.3 expression is observed in 3T3 fibroblasts also. Untransformed 3T3 cells carry abundant 1.9 kb Hox 1.3 RNA, whereas the methylcholanthrene-transformed MB66 and LTK- cells or 3T3 cells transformed by the oncogenes src, fos or SV40 T antigen express only low levels.

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