An evolutionarily conserved N-terminal Sgk1 variant with enhanced stability and improved function

Nandita S Raikwar; Peter M Snyder; Christie P Thomas

doi:10.1152/ajprenal.90239.2008

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An evolutionarily conserved N-terminal Sgk1 variant with enhanced stability and improved function

Journal article

Open access

Peer reviewed

An evolutionarily conserved N-terminal Sgk1 variant with enhanced stability and improved function

Nandita S Raikwar, Peter M Snyder and Christie P Thomas

American journal of physiology. Renal physiology, Vol.295(5), pp.F1440-F1448

11/2008

DOI: 10.1152/ajprenal.90239.2008

PMCID: PMC2653283

PMID: 18753299

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Abstract

Sgk1 is an aldosterone-induced kinase that regulates epithelial sodium channel (ENaC)-mediated Na+ transport in the collecting duct and connecting tubule of the kidney. The NH2 terminus of Sgk1 contains instability motifs that direct the ubiquitination of Sgk1 resulting in a rapidly degraded protein. By bioinformatic analysis, we identified a 5' variant alternate transcript of human Sgk1 (Sgk1_v2) that is widely expressed, is conserved from rodent to humans, and is predicted to encode an Sgk1 isoform, Sgk1_i2, with a different NH2 terminus. When expressed in HEK293 cells, Sgk1_i2 was more abundant than Sgk1 because of an increased protein half-life and this correlated with reduced ubiquitination of Sgk1_i2 and enhanced surface expression of ENaC. Immunocytochemical studies demonstrated that in contrast to Sgk1, Sgk1_i2 is preferentially targeted to the plasma membrane. When coexpressed with ENaC subunits in FRT epithelia, Sgk1_i2 had a significantly greater effect on amiloride-sensitive Na+ transport compared with Sgk1. Together, the data demonstrate that a conserved NH2-terminal variant of Sgk1 shows improved stability, enhanced membrane association, and greater stimulation of epithelial Na+ transport in a heterologous expression system.

Gene Expression Regulation, Enzymologic - drug effects

Conserved Sequence - genetics

Humans

Kidney - enzymology

Brain - enzymology

Molecular Sequence Data

Cytoplasm - metabolism

Epithelial Sodium Channels - metabolism

Immediate-Early Proteins - metabolism

Dexamethasone - pharmacology

Epithelial Sodium Channels - genetics

Transfection

Isoenzymes - metabolism

Cell Membrane - metabolism

Protein-Serine-Threonine Kinases - metabolism

Pancreas - enzymology

Amino Acid Sequence

Cell Line

Isoenzymes - genetics

Enzyme Stability

Protein-Serine-Threonine Kinases - genetics

Rats

Reverse Transcriptase Polymerase Chain Reaction

Sequence Homology, Amino Acid

Animals

Immediate-Early Proteins - genetics

Mice

Microscopy, Fluorescence

Sorbitol - pharmacology

Evolution, Molecular

Details

Title: Subtitle: An evolutionarily conserved N-terminal Sgk1 variant with enhanced stability and improved function
Creators: Nandita S Raikwar - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA, USA
Peter M Snyder
Christie P Thomas
Resource Type: Journal article
Publication Details: American journal of physiology. Renal physiology, Vol.295(5), pp.F1440-F1448
DOI: 10.1152/ajprenal.90239.2008
PMID: 18753299
PMCID: PMC2653283
NLM abbreviation: Am J Physiol Renal Physiol
ISSN: 1931-857X
eISSN: 1522-1466
Publisher: United States
Grant note: HL-71664 / NHLBI NIH HHS HL-058812 / NHLBI NIH HHS R01 HL071664 / NHLBI NIH HHS
Language: English
Date published: 11/2008
Academic Unit: Molecular Physiology and Biophysics; Stead Family Department of Pediatrics; Obstetrics and Gynecology; Medicine Administration; Internal Medicine
Record Identifier: 9983985905602771

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