Receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis is accompanied by intracellular Ca2+ mobilization in a form of oscillations, which plays essential roles by activating sequentially Ca 2+ /calmodulin-dependent protein kinase, calcineurin and NFATc1, necessary in the osteoclast differentiation. However, it is not known whether Ca2+ mobilization which is evoked in RANKL-independent way induces to differentiate into osteoclasts. In present study, we investigated Ca 2+ mobilization induced by aluminum fluoride (AlF4 .), a G-protein activator, with or without RANKL and the effects of AlF4 . on the osteoclastogenesis in primary cultured mouse bone marrow-derived macrophages (BMMs). We show here that AlF4 . induces intracellular Ca2+ concentration ([Ca2+]i) oscillations, which is dependent on extracellular Ca2+ influx. Notably, co-stimulation of AlF4 . with RANKL resulted in enhanced NFATc1 expression and formation of tartrate-resistant acid phosphatase (TRAP) positive multinucleated cells. Additionally, we confirmed that mitogen-activated protein kinase (MAPK) is also activated by AlF4 .. Taken together, these results demonstrate that G-protein would be a novel modulator responsible for [Ca2+]i oscillations and MAPK activation which lead to enhancement of RANKL-mediated osteoclastogenesis.
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