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Overexpression of regucalcin enhances its nuclear localization and suppresses L‐ type Ca 2+ channel and calcium‐sensing receptor mRNA expressions in cloned normal rat kidney proximal tubular epithelial NRK52E cells
Author(s) -
Nakagawa Taeko,
Yamaguchi Masayoshi
Publication year - 2006
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.20863
Subject(s) - medicine , epithelial sodium channel , endocrinology , messenger rna , aldosterone , microbiology and biotechnology , biology , parathyroid hormone , receptor , transfection , chemistry , cell culture , calcium , sodium , gene , biochemistry , genetics , organic chemistry
The effect of regucalcin (RC), a regulatory protein in intracellular signaling pathway, on the gene expression of various mineral ion transport‐related proteins was investigated using the cloned normal rat kidney proximal tubular epithelial NRK52E cells overexpressing RC. NRK52E cells (wild‐type) and stable RC/pCXN2 transfectant were cultured for 72 h in medium containing 5% bovine serum (BS) to obtain subconfluent monolayers. After culture for 72 h, cells were further cultured 24–72 h in a medium containing either vehicle, aldosterone (10 −8 or 10 −7 M), or parathyroid hormone (PTH) (1–34) (10 −8 or 10 −7 M) without BS. RC was markedly localized in the nucleus of transfectants. Overexpression of RC caused a significant increase in rat outer medullary K + channel (ROMK) mRNA expression, while it caused a remarkable decrease in L‐type Ca 2+ channel and calcium‐sensing receptor (CaR) mRNA expressions. Overexpression of RC did not have an effect on epithelial sodium channel (ENaC), Na, K‐ATPase (alpha‐subunit), Type II Na‐Pi cotransporter (NaPi‐IIa), angiotensinogen, Na + ‐Ca 2+ exchanger, and glyceroaldehyde‐3‐phosphate dehydrogenase (G3PDH) mRNA expressions. Hormonal effect on gene expression, moreover, was examined. Culture with aldosterone (10 −8 or 10 −7 M) caused a significant increase in ENaC, Na, K‐ATPase, and ROMK mRNA expressions in the wild‐type cells. Those increases were weakened in the transfectants. Culture with PTH (10 −8 or 10 −7 M) significantly decreased NaPi‐IIa mRNA expression in the wild‐type cells. This effect was not altered in the transfectants. PTH significantly decreased angiotensinogen mRNA expression in the wild‐type cells and the transfectants, while aldosterone had no effect. Culture with PTH (10 −8 or 10 −7 M) caused a significant decrease in L‐ type Ca 2+ channel and CaR mRNA expressions in the wild‐type cells, while the hormone significantly increased Na + ‐Ca 2+ exchanger mRNA expression. The effects of PTH on L‐ type Ca 2+ channel, CaR, and Na + ‐Ca 2+ exchanger mRNA expressions were also seen in the transfectants. This study demonstrates that overexpression of RC caused a remarkable increase in its nuclear localization, and that it has suppressive effects on the gene expression of L‐ type Ca 2+ channel or CaR, which regulates intracellular Ca 2+ signaling, among various regulator proteins for mineral ions in NRK52E cells. J. Cell. Biochem. 99: 1064–1077, 2006. © 2006 Wiley‐Liss, Inc.