Document Detail

Multiplicity of expression of FXYD proteins in mammalian cells: dynamic exchange of phospholemman and gamma-subunit in response to stress.
MedLine Citation:
PMID:  17050615     Owner:  NLM     Status:  MEDLINE    
Functional properties of Na-K-ATPase can be modified by association with FXYD proteins, expressed in a tissue-specific manner. Here we show that expression of FXYDs in cell lines does not necessarily parallel the expression pattern of FXYDs in the tissue(s) from which the cells originate. While being expressed only in lacis cells in the juxtaglomerular apparatus and in blood vessels in kidney, FXYD1 was abundant in renal cell lines of proximal tubule origin (NRK-52E, LLC-PK1, and OK cells). Authenticity of FXYD1 as a part of Na-K-ATPase in NRK-52E cells was demonstrated by co-purification, co-immunoprecipitation, and co-localization. Induction of FXYD2 by hypertonicity (500 mosmol/kgH(2)O with NaCl for 48 h or adaptation to 700 mosmol/kgH(2)O) correlated with downregulation of FXYD1 at mRNA and protein levels. The response to hypertonicity was influenced by serum factors and entailed, first, dephosphorylation of FXYD1 at Ser(68) (1-5 h) and, second, induction of FXYD2a and a decrease in FXYD1 with longer exposure. FXYD1 was completely replaced with FXYD2a in cells adapted to 700 mosmol/kgH(2)O and showed a significantly decreased sodium affinity. Thus dephosphorylation of FXYD1 followed by exchange of regulatory subunits is utilized to make a smooth transition of properties of Na-K-ATPase. We also observed expression of mRNA for multiple FXYDs in various cell lines. The expression was dynamic and responsive to physiological stimuli. Moreover, we demonstrated expression of FXYD5 protein in HEK-293 and HeLa cells. The data imply that FXYDs are obligatory rather than auxiliary components of Na-K-ATPase, and their interchangeability underlies responses of Na-K-ATPase to cellular stress.
Elena Arystarkhova; Claudia Donnet; Ana Muñoz-Matta; Susan C Specht; Kathleen J Sweadner
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2006-10-18
Journal Detail:
Title:  American journal of physiology. Cell physiology     Volume:  292     ISSN:  0363-6143     ISO Abbreviation:  Am. J. Physiol., Cell Physiol.     Publication Date:  2007 Mar 
Date Detail:
Created Date:  2007-03-09     Completed Date:  2007-04-24     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  100901225     Medline TA:  Am J Physiol Cell Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  C1179-91     Citation Subset:  IM    
Laboratory of Membrane Biology, Massachusetts General Hospital, Boston, MA 02114, USA.
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MeSH Terms
Cell Line
Gene Expression / physiology*
Membrane Proteins / metabolism*
Organ Specificity
Oxidative Stress / physiology*
Phosphoproteins / metabolism*
Protein Subunits / metabolism
Sodium-Potassium-Exchanging ATPase / chemistry,  metabolism*
Grant Support
Reg. No./Substance:
0/Membrane Proteins; 0/Phosphoproteins; 0/Protein Subunits; 135541-82-1/phospholemman; EC ATPase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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