Unique uptake and efflux systems of inorganic phosphate in osteoclast-like cells
Unique uptake and efflux systems of inorganic phosphate in osteoclast-like cells
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DOI：
10.1152/ajpcell.00357.2006
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发表时间：
2007-01-01
影响因子：
5.5
通讯作者：
Miyamoto, Ken-ichi
中科院分区：
文献类型：
--
作者：
Ito, Mikiko;Haito, Sakiko;Miyamoto, Ken-ichi
在骨吸收过程中，破骨细胞半空泡内产生大量的无机磷酸盐（Pi）。这种P-i的处置所涉及的机制尚不清楚。在本研究中，我们研究了破骨细胞样细胞的P-i外排。在用核因子-κ B配体的受体激活剂处理的RAW 264.7细胞衍生的破骨细胞样细胞中，酸性条件激活了P-i流出。在肾近端小管样负鼠肾细胞、成骨细胞样MC 3 T3-E1细胞或未处理的RAW 264.7细胞中未观察到酸诱导的P-i内流。此外，细胞外P-i和几种P-i类似物[膦酰基甲酸（PFA），膦酰基乙酸，砷酸盐和焦磷酸盐]刺激P-i流出。P-i外排是时间依赖性的，10 min后50%释放到培养基中。P-i的外排增加了各种抑制剂，阻止P-i摄取，和细胞外P-i不影响[C-14] PFA的运输到破骨细胞样细胞。用P-i预加载细胞不刺激PFA的P-i流出，表明P-i的作用不是由于P-i转运的反式刺激。在酸性条件下，P-1吸收也增强。防止胞质游离Ca 2+浓度增加的药物，包括1，2-双（2-氨基苯氧基）乙烷-N，N，N ′，N ′-四乙酸的乙酰氧基甲酯、2-氨基乙氧基二苯基硼酸酯和邦克雷克酸，显著抑制破骨细胞样细胞中的P-1摄取，表明破骨细胞样细胞的内质网和线粒体中的Ca 2+信号调节P-1摄取。这些结果表明，破骨细胞样细胞有一个独特的P-i摄取/流出系统，可以防止P-i积累在破骨细胞半空泡。
During bone resorption, a large amount of inorganic phosphate (P-i) is generated within the osteoclast hemivacuole. The mechanisms involved in the disposal of this P-i are not clear. In the present study, we investigated the efflux of P-i from osteoclast-like cells. P-i efflux was activated by acidic conditions in osteoclast-like cells derived by the treatment of RAW264.7 cells with receptor activator of nuclear factor-kappa B ligand. Acid-induced P-i influx was not observed in renal proximal tubule-like opossum kidney cells, osteoblast-like MC3T3-E1 cells, or untreated RAW264.7 cells. Furthermore, P-i efflux was stimulated by extracellular P-i and several P-i analogs [phosphonoformic acid (PFA), phosphonoacetic acid, arsenate, and pyrophosphate]. P-i efflux was time dependent, with 50% released into the medium after 10 min. The efflux of P-i was increased by various inhibitors that block P-i uptake, and extracellular P-i did not affect the transport of [C-14] PFA into the osteoclast-like cells. Preloading of cells with P-i did not stimulate P-i efflux by PFA, indicating that the effect of P-i was not due to transstimulation of P-i transport. P-i uptake was also enhanced under acidic conditions. Agents that prevent increases in cytosolic free Ca2+ concentration, including acetoxymethyl ester of 1,2-bis(2-aminophenoxy) ethane-N, N, N', N'-tetraacetic acid, 2-aminoethoxydiphenyl borate, and bongkrekic acid, significantly inhibited P-i uptake in the osteoclast-like cells, suggesting that P-i uptake is regulated by Ca2+ signaling in the endoplasmic reticulum and mitochondria of osteoclast-like cells. These results suggest that osteoclast-like cells have a unique P-i uptake/efflux system and can prevent P-i accumulation within osteoclast hemivacuoles.