[Basic and clinical aspects of calcimimetics. Structure and function of calcium-sensing receptor].

Calcium-sensing receptor (CaSR) is a G-protein coupled receptor identified as a essential molecule for the regulation of parathyroid hormone (PTH) secretion by extracellular calcium (Ca). Binding of extracellular Ca to CaSR activates several intracellular signaling pathways including increase of intracellular Ca, and inhibits PTH secretion. CaSR is expressed in several tissues other than parathyroid glands including kidney and C-cells in thyroid, and contributes to enhanced renal excretion of Ca and secretion of calcitonin in response to the increase of extracellular Ca. The importance of CaSR in the maintenance of extracellular Ca is also shown by hypercalcemic and hypocalcemic diseases caused by inactivating and activating mutations in CaSR gene, respectively.