scholarly journals Human epithelial Na+ channel missense variants identified in the GenSalt study alter channel activity

2016 ◽  
Vol 311 (5) ◽  
pp. F908-F914 ◽  
Author(s):  
Evan C. Ray ◽  
Jingxin Chen ◽  
Tanika N. Kelly ◽  
Jiang He ◽  
L. Lee Hamm ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Cell Surface ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Channel Activity ◽  
Dietary Salt ◽  
Α Subunit ◽  
Γ Subunit ◽  
Genes Encoding ◽  
Altered Sensitivity

Mutations in genes encoding subunits of the epithelial Na+ channel (ENaC) can cause early onset familial hypertension, demonstrating the importance of this channel in modulating blood pressure. It remains unclear whether other genetic variants resulting in subtler alterations of channel function result in hypertension or altered sensitivity of blood pressure to dietary salt. This study sought to identify functional human ENaC variants to examine how these variants alter channel activity and to explore whether these variants are associated with altered sensitivity of blood pressure to dietary salt. Six-hundred participants of the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) study with salt-sensitive or salt-resistant blood pressure underwent sequencing of the genes encoding ENaC subunits. Functional effects of identified variants were examined in a Xenopus oocyte expression system. Variants that increased channel activity included three in the gene encoding the α-subunit (αS115N, αR476W, and αV481M), one in the β-subunit (βS635N), and one in the γ-subunit (γL438Q). One α-subunit variant (αA334T) and one γ-subunit variant (βD31N) decreased channel activity. Several α-subunit extracellular domain variants altered channel inhibition by extracellular Na+ (Na+ self-inhibition). One variant (αA334T) decreased and one (αV481M) increased cell surface expression. Association between these variants and salt sensitivity did not reach statistical significance. This study identifies novel functional human ENaC variants and demonstrates that some variants alter channel cell surface expression and/or Na+ self-inhibition.

Cell surface expression and turnover of the α-subunit of the epithelial sodium channel

2001 ◽  
Vol 281 (2) ◽  
pp. F213-F221 ◽  
Author(s):  
Thomas R. Kleyman ◽  
Jonathan B. Zuckerman ◽  
Pamela Middleton ◽  
Kathleen A. McNulty ◽  
Baofeng Hu ◽  
...  
Keyword(s):  
Cell Surface ◽  
Hormonal Regulation ◽  
Short Circuit ◽  
Apical Cell ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Apical Surface ◽  
Open Probability ◽  
Α Subunit ◽  
A6 Cells

The renal epithelial cell line A6, derived from Xenopus laevis, expresses epithelial Na+ channels (ENaCs) and serves as a model system to study hormonal regulation and turnover of ENaCs. Our previous studies suggest that the α-subunit of Xenopus ENaC (α- xENaC) is detectable as 150- and 180-kDa polypeptides, putative immature and mature α-subunit heterodimers. The 150- and 180-kDa α- xENaC were present in distinct fractions after sedimentation of A6 cell lysate through a sucrose density gradient. Two anti-α- xENaC antibodies directed against distinct domains demonstrated that only 180-kDa α- xENaC was expressed at the apical cell surface. The half-life of cell surface-expressed α- xENaC was 24–30 h, suggesting that once ENaC matures and is expressed at the plasma membrane, its turnover is similar to that reported for mature cystic fibrosis transmembrane conductance regulator. No significant changes in apical surface expression of α- xENaC were observed after treatment of A6 cells with aldosterone for 24 h, despite a 5.3-fold increase in short-circuit current. This lack of change in surface expression is consistent with previous observations in A6 cells and suggests that aldosterone regulates ENaC gating and increases channel open probability.

scholarly journals Structural mutation affecting intracellular transport and cell surface expression of murine class II molecules.

1988 ◽  
Vol 167 (2) ◽  
pp. 541-555 ◽  
Author(s):  
I J Griffith ◽  
N Nabavi ◽  
Z Ghogawala ◽  
C G Chase ◽  
M Rodriguez ◽  
...  
Keyword(s):  
Cell Surface ◽  
Intracellular Transport ◽  
B Cell Lymphoma ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Single Nucleotide ◽  
Secondary Structure Analysis ◽  
Genes Encoding ◽  
Cytoplasmic Accumulation ◽  
Negative Signal

We have selected Ia variants from the Ia+ (H-2d) M12.4.1 B cell lymphoma that are negative on the cell surface for one or both Ia isotypes. The molecular analysis of two such independently selected cell lines, M12.A2 and M12.C3, is reported here. This analysis revealed that the genes encoding Ad beta (M12.A2) and Ed beta (M12.C3) contained identical single-nucleotide transitions that resulted in the substitution of Ser (mutant) for Asn (wild-type) at residue 82/83 of the extracellular NH2-terminal (membrane distal) beta 1 domain. This conservative substitution caused a cytoplasmic accumulation of I-A or I-E molecules in the respective cell line although predicted secondary-structure analysis suggests a minimal effect on protein conformation. Thus, the mutation appears to have either created a negative signal that stops transport or eliminated a positive signal that is required for transport and targeting to the cell surface.

Unusual degradation of α-β complexes inXenopusoocytes by β-subunits ofXenopusgastric H-K-ATPase

1998 ◽  
Vol 275 (1) ◽  
pp. C139-C145 ◽  
Author(s):  
Pei-Xian Chen ◽  
Paul M. Mathews ◽  
Peter J. Good ◽  
Bernard C. Rossier ◽  
Käthi Geering
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Surface ◽  
Xenopus Oocytes ◽  
Experimental System ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Β Subunit ◽  
Α Subunit ◽  
P Type ◽  
Α Subunits

The catalytic α-subunit of oligomeric P-type ATPases such as Na-K-ATPase and H-K-ATPase requires association with a β-subunit after synthesis in the endoplasmic reticulum (ER) to become stably expressed and functionally active. In this study, we have expressed the β-subunit of Xenopus gastric H-K-ATPase (βHK) in Xenopus oocytes together with α-subunits of H-K-ATPase (αHK) or Na-K-ATPase (αNK) and have followed the biosynthesis, assembly, and cell surface expression of functional pumps. Immunoprecipitations of Xenopus βHK from metabolically labeled oocytes show that it is well expressed and, when synthesized without α-subunits, can leave the ER and become fully glycosylated. Xenopus βHK can associate with both coexpressed αHK and αNK, but the α-β complexes formed are degraded rapidly in or close to the ER and do not produce functional pumps at the cell surface as assessed by86Rb uptake. A possible explanation of these results is that Xenopus βHK may contain a tissue-specific signal that is important in the formation or correct targeting of functional α-β complexes in the stomach but that cannot be recognized in Xenopusoocytes and in consequence leads to cellular degradation of the α-β complexes in this experimental system.

scholarly journals Mice carrying ubiquitin-specific protease 2 (Usp2) gene inactivation maintain normal sodium balance and blood pressure

2013 ◽  
Vol 305 (1) ◽  
pp. F21-F30 ◽  
Author(s):  
Daniel Pouly ◽  
Anne Debonneville ◽  
Dorothée Ruffieux-Daidié ◽  
Marc Maillard ◽  
Hugues Abriel ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Cell Surface ◽  
Surface Expression ◽  
Gene Inactivation ◽  
Cell Surface Expression ◽  
Sodium Balance ◽  
Standard Diet ◽  
Primary Role ◽  
Rhythmic Expression

Ubiquitylation plays an important role in the control of Na+ homeostasis by the kidney. It is well established that the epithelial Na+ channel ENaC is regulated by the ubiquitin-protein ligase NEDD4-2, limiting ENaC cell surface expression and activity. Ubiquitylation can be reversed by the action of deubiquitylating enzymes (DUBs). One such DUB, USP2-45, was identified previously as an aldosterone-induced protein in the kidney and is also a circadian output gene. In heterologous expression systems, USP2-45 binds to ENaC, deubiquitylates it, and enhances channel density and activity at the cell surface. Because the role of USP2-45 in renal Na+ transport had not been studied in vivo, we investigated here the effect of Usp2 gene inactivation in this process. We demonstrate first that USP2-45 protein has a rhythmic expression with a peak at ZT12. Usp2-KO mice did not show any differences from wild-type littermates with respect to the diurnal control of Na+ or K+ urinary excretion and plasma levels either on a standard diet or after acute and chronic changes to low- and high-Na+ diets, respectively. Moreover, they had similar aldosterone levels on either a low- or high-Na+ diet. Blood pressure measurements using telemetry did not reveal variations compared with control mice. Usp2-KO mice did not display alterations in expression of genes involved in sodium homeostasis or the ubiquitin system, as evidenced by transcriptome analysis in the kidney. Our data suggest that USP2 does not play a primary role in the control of Na+ balance or blood pressure.

Glutamate transporter GLAST/EAAT1 directs cell surface expression of FXYD2/γ subunit of Na, K-ATPase in human fetal astrocytes

2007 ◽  
Vol 50 (7-8) ◽  
pp. 916-920 ◽  
Author(s):  
M GEGELASHVILI ◽  
A RODRIGUEZKERN ◽  
L SUNG ◽  
K SHIMAMOTO ◽  
G GEGELASHVILI
Keyword(s):  
Cell Surface ◽  
Glutamate Transporter ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Γ Subunit

Persistent HIV Transcription Induces Sialyl-Lewis-X Glyco-Antigen Cell-Surface Expression

2020 ◽  
Author(s):  
Florent Colomb ◽  
Leila B. Giron ◽  
Leticia Kuri Cervantes ◽  
Tongcui Ma ◽  
Samson Adeniji ◽  
...  
Keyword(s):  
Cell Surface ◽  
Surface Expression ◽  
Sialyl Lewis X ◽  
Cell Surface Expression ◽  
Lewis X ◽  
Hiv Transcription ◽  
Sialyl Lewis
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