Characterization of inorganic phosphate transport in osteoclast-like cells
Characterization of inorganic phosphate transport in osteoclast-like cells
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DOI：
10.1152/ajpcell.00412.2004
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发表时间：
2005-04-01
影响因子：
5.5
通讯作者：
Miyamoto, K
中科院分区：
文献类型：
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作者：
Ito, M;Matsuka, N;Miyamoto, K
破骨细胞拥有无机磷酸盐 (P-i) 运输系统，可在骨吸收过程中吸收外部 P-i。在本研究中，我们表征了小鼠破骨细胞样细胞中的 P-i 转运，这些细胞是通过用 NF-κ B 配体受体激活剂 (RANKL) 分化巨噬细胞 RAW264.7 细胞而获得的。在未分化的RAW264.7细胞中，P-i向细胞内的转运是Na+依赖性的，但用RANKL处理后，不依赖于Na+的P-i转运显着增加。此外，与中性pH相比，破骨细胞样细胞中不依赖Na+的P-i转运系统的活性在pH 5.5时显着增强。 Na+ 独立系统由 K-m 分别为 0.35 mM 和 7.5 mM 的两个组件组成。 P-i 转运抑制剂、膦甲酸和砷酸盐显着降低了 P-i 转运。质子离子载体尼日利亚霉素和羰基氰化物对三氟甲氧基苯腙以及 K+ 离子载体缬氨霉素显着抑制 P-i 转运活性。 BCECF 荧光分析表明破骨细胞样细胞中的 P-i 运输与质子运输系统偶联。此外，细胞外K+离子的升高刺激P-i转运，表明膜电压参与P-i转运活性的调节。最后，骨颗粒显着增加了破骨细胞样细胞中不依赖 Na+ 的 P-i 转运活性。因此，破骨细胞样细胞具有Pi转运系统，其特征不同于其他Na+依赖性Pi转运蛋白。我们得出的结论是，在酸性 pH 值下刺激 P-i 运输对于骨吸收或产生酸化细胞外环境所需的大量能量是必要的。
Osteoclasts possess inorganic phosphate ( P-i) transport systems to take up external P-i during bone resorption. In the present study, we characterized P-i transport in mouse osteoclast-like cells that were obtained by differentiation of macrophage RAW264.7 cells with receptor activator of NF-kappa B ligand ( RANKL). In undifferentiated RAW264.7 cells, P-i transport into the cells was Na+ dependent, but after treatment with RANKL, Na+-independent P-i transport was significantly increased. In addition, compared with neutral pH, the activity of the Na+-independent P-i transport system in the osteoclast-like cells was markedly enhanced at pH 5.5. The Na+-independent system consisted of two components with K-m of 0.35 mM and 7.5 mM. The inhibitors of P-i transport, phosphonoformic acid, and arsenate substantially decreased P-i transport. The proton ionophores nigericin and carbonyl cyanide p-trifluoromethoxyphenylhydrazone as well as a K+ ionophore, valinomycin, significantly suppressed P-i transport activity. Analysis of BCECF fluorescence indicated that P-i transport in osteoclast-like cells is coupled to a proton transport system. In addition, elevation of extracellular K+ ion stimulated P-i transport, suggesting that membrane voltage is involved in the regulation of P-i transport activity. Finally, bone particles significantly increased Na+- independent P-i transport activity in osteoclast- like cells. Thus, osteoclast- like cells have a Pi transport system with characteristics that are different from those of other Na+- dependent P-i transporters. We conclude that stimulation of P-i transport at acidic pH is necessary for bone resorption or for production of the large amounts of energy necessary for acidification of the extracellular environment.