Regucalcin, cell signalling-related protein: its multifunctional role in kidney cell regulation

Introduction Regucalcin was discovered in 1978 as a calcium-binding protein that does not contain EF-hand motif of calcium-binding domain, which differs from calmodulin and other calcium-related proteins. The regucalcin gene is localized on the X chromosome. Regucalcin is greatly pronounced in hepatocytes and kidney proximal tubular cells. This review provides recent information concerning the role of regucalcin in the regulation of kidney cell function. Discussion Regucalcin has been demonstrated to play a physiological role in the regulation of Ca2+ homeostasis in the kidney proximal tubular epithelial cells, which participate in transcellular transport to reabsorption of calcium from filtrated urinary calcium. Regucalcin also regulates various enzyme activities including Ca2+-dependent protein kinases, protein phosphatases, nitric oxide synthase and others, which are involved in intracellular signalling pathways. Regucalcin is localized to the nucleus and regulates the gene expressions of proteins, which are related to mineral transport-related proteins, Smad 2, the nuclear factor-kappa B, cell proliferation and apoptosis-related proteins in the kidney tubular epithelial cells. Conclusion This review proposes that regucalcin plays a pivotal role as a multi-functional protein in the regulation of kidney proximal tubular epithelial cells. It reveals a suppressive effect on cell proliferation and apoptotic death, through signalling stimulators and hypertensive state or developing drug-induced kidney disorders.