ISSN:
1432-1424
Keywords:
potassium channel
;
molecular cloning
;
Na+ K+-ATPase pump
;
renal proximal tubule
;
salivary duct
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary We previously reported a novel rat membrane protein that exhibits a voltage-dependent potassium channel activity on the basis of molecular cloning combined with an electrophysiological assay. This protein, termedI sK protein, is small and different from the conventional potassium channel poroteins but induces selective permeation of potassium ions on its expression inXenopus oocytes. In this investigatiion, we examined cellular localization of ratI sK protein by preparing three different types of antibody that specifically reacts with a distinct part of ratI sK protein. Immunohistochemical analysis using these antibody preparations demonstrated that ratI sK protein is confined to the apical membrane portion of epithelial cells in the proximal tubule of the kidney, the submandibular duct and the uterine endometrium. The observed tissue distribution of ratI sK protein was consistent with that of theI sK protein mRNA determined by blot hybridization analysis. In epithelial cells the sodium, potassium-ATPase pump in the basolateral membrane generats a sodium gradient acrossthe epithelial cell and allows sodium ions to entere the cell through the apical membrane. Thus, taking into account the cellular localization of theI sK protein, together with its electrophysiological properties, we discussed a possible function of theI sK protein, namely that this protein is involved in potassium permeation in the apical membrane of epithelial cells through the depolarizing effect of sodium entry.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01869604
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