Calcium sensing receptors as integrators of multiple metabolic signals.

Calcium sensing receptors are critical to maintenance of organismal Ca2+ homeostasis, translating small changes in serum Ca2+ into changes in PTH secretion by the parathyroid glands and Ca2+ excretion by the kidneys. Calcium sensing receptors are also expressed in many cells and tissues not directly involved in Ca2+ homeostasis where their role(s) are less defined. Recent studies have demonstrated that calcium sensing receptors integrate a variety of metabolic signals, including polyvalent cations, pH, ionic strength, amino acids, and polypeptides, making CaR uniquely capable of generating cell- and tissue-specific responses, sensing not only Ca2+, but the local metabolic environment. The challenge for future studies is to define CaR responsiveness in each varied physiological context.