Overexpression of regucalcin suppresses Ca2+‐sensing receptor and L‐type Ca2+ channel mRNA expression in cloned rat kidney proximal tubular NRK52E cells

Abstract

The effect of regucalcin, a regulatory protein in intracellular signaling pathway [Yamaguchi M, Int J Mol Med 15:372–389, 2005 in Review], on various gene expressions was investigated using the cloned normal rat kidney proximal tubular epithelial NRK52E cells overexpressing regucalcin. NRK52E cells (wild type) and stable regucalcin /pCXN2 transfectants were cultured for 72 hours in medium containing 5% bovine serum to obtain subconfluent monolayers. After culture, cells were further cultured for 24–72 hours in serum free medium. Regucalcin was localized in the nucleus of wild type cells. This localization was markedly increased in transfectants. Overexpression of regucalcin caused a significant increase in rat outer medullary K+ channel mRNA expression, while it did not cause epithelial sodium channel, Na+-K+-ATPase, type II Na-Pi cotransporter, angiotensinogen and Na+/Ca+ exchanger mRNA expressions in transfectants. The expression of Ca2+-sensing receptor and L-type Ca2+ channel mRNA was markedly suppressed in transfectants. Thses decreases were changed in the presence of parathyroid hormone that can suppress the gene expression. This study demonstrates that regucalcin has a role in the regulation of gene expression for Ca2+-sensing receptor and L-type Ca2+ channel that is involved in intracellular Ca2+ transport in kidney cells.