Activation of G Proteins by Aluminum Fluoride Enhances RANKL- Mediated Osteoclastogenesis

Activation of G Proteins by Aluminum Fluoride Enhances RANKL- Mediated Osteoclastogenesis

Receptor activator of NF-&#1354;B ligand (RANKL)-induced osteoclastogenesis is accompanied by intra-cellular Ca<SUP>2＋</SUP> mobilization in a form of oscillations, which plays essential roles by activating sequen-tially Ca<SUP>2＋</SUP>/calmodulin-dependent protein kinase, calcineurin and NFATc1, necessary in the osteoclast differentiation. However, it is not known whether Ca<SUP>2＋</SUP> mobilization which is evoked in RANKL-in-dependent way induces to differentiate into osteoclasts. In present study, we investigated Ca<SUP>2＋</SUP> mobilization induced by aluminum fluoride (AlF<SUB>4</SUB><SUP>&#8722;</SUP>), a G-protein activator, with or without RANKL and the effects of AlF<SUB>4</SUB>&#8722; on the osteoclastogenesis in primary cultured mouse bone marrow-derived macrophages (BMMs). We show here that AlF<SUB>4</SUB><SUP>&#8722;</SUP> induces intracellular Ca<SUP>2＋</SUP> concentration ([Ca<SUP>2＋</SUP>]i) oscillations, which is dependent on extracellular Ca<SUP>2＋</SUP> influx. Notably, co-stimulation of AlF<SUB>4</SUB><SUP>&#8722;</SUP> 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 AlF<SUB>4</SUB><SUP>&#8722;</SUP>. Taken together, these results demonstrate that G-protein would be a novel modulator responsible for [Ca<SUP>2＋</SUP>]i oscillations and MAPK activation which lead to enhancement of RANKL-mediated osteoclastogenesis.