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IRBIT reduces the apparent affinity for intracellular Mg(2+) in inhibition of the electrogenic Na(+)-HCO(3)(-) cotransporter NBCe1-B.
MedLine Citation:
PMID:  22771795     Owner:  NLM     Status:  Publisher    
The electrogenic Na(+)-HCO(3)(-) cotransporter NBCe1-B can be regulated by intracellular Mg(2+) (Mg(2+)(i)). We previously reported that under whole-cell voltage-clamp conditions, bovine NBCe1-B (bNBCe1-B) currents heterologously expressed in mammalian cells are strongly inhibited by Mg(2+)(i), and the inhibition is likely mediated by electrostatic interaction and relieved by truncation of the cytosolic NBCe1-B specific N-terminal region. Intriguingly, NBCe1-B-like currents natively expressed in bovine parotid acinar (BPA) cells are much less sensitive to Mg(2+)(i) inhibition than bNBCe1-B currents. Here, we hypothesized that this apparent discrepancy may involve IRBIT, a previously identified NBCe1-B-interacting protein. RT-PCR, Western blot and immunofluorescence confocal microscopy revealed that IRBIT was not only expressed in the cytosol, but also colocalized with NBCe1-B in the region of plasma membranes of BPA cells. IRBIT was coimmunoprecipitated with NBCe1-B by an anti-NBCe1 antibody in bovine parotid cell lysate. Whole-cell patch-clamp experiments showed that coexpression of IRBIT lowered the Mg(2+)(i) sensitivity of bNBCe1-B currents stably expressed in HEK293 cells. Collectively, these results suggest that IRBIT may reduce the apparent affinity for Mg(2+)(i) in inhibition of NBCe1-B activity in mammalian cells.
Soichiro Yamaguchi; Toru Ishikawa
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-3
Journal Detail:
Title:  Biochemical and biophysical research communications     Volume:  -     ISSN:  1090-2104     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-9     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0372516     Medline TA:  Biochem Biophys Res Commun     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012. Published by Elsevier Inc.
Laboratory of Physiology, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
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