Role of transient receptor potential(TRP) of Ca^<2+>-permeable cation channels in osteoclast apoptosis

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Osteoclasts express TRPM7, a Ca^<2+-> and Mg^<2+-> permeable cation channel. However, the functional role of TRPM7 in osteoclasts is unknown. We examined the properties of cation transport through TRPM7 in mature osteoclasts and further investigated the contribution of TRPM7 to osteoclast apoptosis. Although cation transport via TRPM7 was inactive in the presence of physiological concentration of Mg^<2+>, extracellular acidification abrogated the Mg^<2+-> dependent blockade. Osteoclasts extrude H+and Cl-and form an acidic compartment to dissolve inorganic component of bone matrix. Abrogation of Mg^<2+-> dependent block of cation transport at acidic extracellular milieu is convenient for uptake of Ca^<2+> and Mg^<2+> eluted from bone during bone resorption. Our evidence also showed that TRPM7 was less likely to participate in osteoclast apoptosis.