Regucalcin is a Ca2+ binding protein that is encoded by a highly conserved gene in vertebrate species. Regucalcin is greatly expressed in liver and kidney cortex, and the expression is mediated through a Ca2+ signaling mechanism with AP1 and NFI-A1 as transcriptional factors. It plays a multifunctional role as a regulatory protein in intracellular signaling processes in the cytoplasm and nucleus of cells including the maintenance of intracellular Ca2+ homeostasis, the regulation of various