A novel calcium sensor stimulating inositol phosphate formation and [Ca2+](i) signaling expressed by GCT23 osteoclast-like cells

Osteoclast activity is inhibited by elevated [Ca2+](o); however. the: underlying molecular mechanism is unknown. We used the human osteoclast-like cells GCT23 to elucidate their cation-sensing properties. Cells responded to elevated [Ca2+](o) with rapid concentration-dependent [Ca2+](i) transients (EC50 = 7.8 mm, time to peak 44 +/- 4 sec) that were due to release from intracellular stores, followed by Ca2+ Influx across the plasma membrane. Ca2+ store depletion by thapsigargin, endothelin-l, or bradykinin activated calcium entry pathways. Cells responded similarly to Ni2+ and Cd2+ with albeit slower kinetics (EC50