Nucleic acids encoding human calcium sensor protein

The present invention relates to the isolation of a cDNA clone encoding the calcium sensor in human placenta and subsequent Northern blots confirming the mRNA expression also in human parathyroid and kidney tubule cells. Close sequence similarity is demonstrated with the rat Heymann nephritis antigen, a glycoprotein of the kidney tubule brush border with calcium binding ability. Immunohistochemistry substantiates a tissue distribution of the calcium sensor protein similar to that previously described for the Heymann antigen. It is proposed that the identified calcium sensor protein constitutes a universal sensor for recognition of variation in extracellular calcium, and that it plays a key role for calcium regulation via different organ systems. The calcium sensor protein belongs to the LDL-superfamily of glycoproteins, claimed to function primarily as protein receptors, but with functionally important calcium binding capacity.