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Distribution and regulation of expression of serum‐ and glucocorticoid‐induced kinase‐1 in the rat kidney
Author(s) -
Rosa Diego Alvarez,
Coric Tatjana,
Todorovic Natasa,
Shao Deren,
Wang Tong,
Canessa Cecilia M.
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2003.042903
Subject(s) - sgk1 , gene isoform , aldosterone , kidney , epithelial polarity , medicine , glucocorticoid , endocrinology , biology , basal (medicine) , epithelial sodium channel , microbiology and biotechnology , blot , chemistry , cell , biochemistry , organic chemistry , insulin , gene , sodium
The serum‐ and glucocorticoid‐induced kinase‐1 (sgk1) increases the activity of a number of epithelial ion channels and transporters. The present study examines the distribution and subcellular localization of sgk1 protein in the rat kidney and the regulation of levels of expression induced by steroids. The results indicate that the kidney expresses predominantly the sgk1 isoform with a distribution restricted to the thick ascending limb of Henle, distal convoluted, connecting and cortical collecting tubules. Within cells, sgk1 strongly associates with the microsomal fraction of homogenates and it colocalizes with the Na + ,K + ‐ATPase to the basolateral membrane. Analysis of the levels of expression of sgk1 by Western blotting and immunohistochemistry indicates constitutive high expression under basal conditions. Approximately half of the basal level is maintained by glucocorticoids whereas physiological fluctuations of aldosterone produce minor changes in sgk1 abundance in adrenal‐intact animals. These results do not support the notion that physiological changes of aldosterone concentration turn the expression of sgk1 ‘on and off’ in the mammalian kidney. Additionally, localization of sgk1 to the basolateral membrane indicates that the effects mediated by sgk1 do not require a direct interaction with the ion channels and transporters whose activity is modulated, since most of these proteins are located in the apical membrane of renal epithelial cells.