Document Detail

Regulation of Kir4.1 and AQP4 expression and stability at the basolateral domain of epithelial MDCK cells by the extracellular matrix.
MedLine Citation:
PMID:  21543416     Owner:  NLM     Status:  MEDLINE    
The proper targeting of ion channels to specialized domains is crucial for cell function. Kir4.1, the inwardly rectifying potassium channel, and aquaporin-4 (AQP4), the type 4 water-permeable channel, are localized at the basolateral domain of polarized epithelial cells; however, the mechanisms involved in their localization have yet to be determined. In this study, we investigated the role of the extracellular matrix in the localization of these channels in polarized Madin-Darby canine kidney (MDCK) cells. MDCK cells expressing green fluorescent protein-Kir4.1 or -AQP4 were cultured on laminin-1 or fibronectin and examined by confocal microscopy and cell surface biotinylation to assess plasma membrane expression of Kir4.1 and AQP4. Our data show that laminin-1 and fibronectin induce a significant increase in cell surface expression of both channels at the basolateral domain. Using fluorescence recovery after photobleaching, we demonstrate that laminin-1 and fibronectin reduce the diffusion rates of these channels. Finally, we show that the laminin receptor dystroglycan is important for cell surface expression of Kir4.1 but not AQP4. However, laminin-1 increases cell surface expression of both channels in cells deficient for dystroglycan, indicating that other receptors are involved. Indeed, RGD-containing peptides, which inhibit fibronectin binding to certain integrins, prevent the fibronectin-induced increase in Kir4.1 and AQP4 cell surface expression and reverse the laminin- and fibronectin-induced reduction in both channels' diffusion rates. Similarly, the αvβ3-integrin function-blocking antibody alters the reduction of AQP4 diffusion rates induced by both laminin and fibronectin, suggesting that αvβ3-integrin plays a role in the stabilization of APQ4 at the basolateral domain of epithelial cells.
Daniel Kai Long Tham; Hakima Moukhles
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2011-05-04
Journal Detail:
Title:  American journal of physiology. Renal physiology     Volume:  301     ISSN:  1522-1466     ISO Abbreviation:  Am. J. Physiol. Renal Physiol.     Publication Date:  2011 Aug 
Date Detail:
Created Date:  2011-08-05     Completed Date:  2011-10-03     Revised Date:  2013-06-30    
Medline Journal Info:
Nlm Unique ID:  100901990     Medline TA:  Am J Physiol Renal Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  F396-409     Citation Subset:  IM    
Dept of Cellular and Physiological Sciences, Univ. of British Columbia, Vancouver, Canada.
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MeSH Terms
Aquaporin 4 / metabolism*
Cell Line
Dystroglycans / metabolism
Dystrophin-Associated Proteins / metabolism
Epithelial Cells / metabolism*
Extracellular Matrix / metabolism*
Kidney / cytology,  metabolism
Membrane Glycoproteins / metabolism*
Potassium Channels, Inwardly Rectifying / metabolism*
Reg. No./Substance:
0/Aquaporin 4; 0/Dystrophin-Associated Proteins; 0/Membrane Glycoproteins; 0/Potassium Channels, Inwardly Rectifying; 0/potassium inwardly-rectifying channel, subfamily J, member 10; 0/syntrophin; 146888-27-9/Dystroglycans

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