Regulation of sodium-dependent phosphate transport in osteoclasts
Regulation of sodium-dependent phosphate transport in osteoclasts
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DOI：
10.1172/jci119563
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发表时间：
1997-08-01
影响因子：
15.9
通讯作者：
Hruska, KA
中科院分区：
文献类型：
--
作者：
Gupta, A;Guo, XL;Hruska, KA
破骨细胞是负责骨吸收的主要细胞，在骨吸收过程中，破骨细胞暴露于高浓度的无机磷（Pi），破骨细胞具有特异性的Pi转运系统，能够吸收骨吸收释放的Pi。我们证实了先前的研究表明在破骨细胞中存在与肾小管“NaPi”蛋白相关的Na依赖性Pi转运蛋白，使用多克隆抗体NaPi-2（大鼠变体），一个类似的95 kD蛋白被检测到，定位在离散的囊泡在玻璃盖玻片上培养的非极化破骨细胞。然而，在极化破骨细胞培养的骨，免疫荧光研究表明，该蛋白只定位在基底外侧膜上，在那里它与钠-氢交换器共定位，但相反的空泡H-ATP酶的本地化，磷脂酰肌醇3-激酶，渥曼青霉素的抑制剂，和肌动蛋白细胞骨架组织，细胞松弛素D的抑制剂，阻止骨刺激增加Pi的吸收。磷酸甲酸（PFA）是一种肾脏NaPi协同转运蛋白的抑制剂，可抑制破骨细胞对NaPi的摄取，PFA对骨吸收也有剂量依赖性的抑制作用，PFA可抑制破骨细胞对ATP的产生。
Osteoclasts are the primary cells responsible for bone resorption, They are exposed to high ambient concentrations of inorganic phosphate (Pi) during the process of bone resorption and they possess specific Pi-transport system(s) capable of taking up Pi released by bone resorption, By immunochemical studies and PCR, we confirmed previous studies suggesting the presence of an Na-dependent Pi transporter related to the renal tubular ''NaPi'' proteins in the osteoclast, Using polyclonal antibodies to NaPi-2 (the rat variant), an similar to 95-kD protein was detected, localized in discrete vesicles in unpolarized osteoclasts cultured on glass coverslips. However, in polarized osteoclasts cultured on bone, immunofluorescence studies demonstrated the protein to be localized exclusively on the basolateral membrane, where it colocalizes with an Na-H exchanger but opposite to localization of the vacuolar H-ATPase, An inhibitor of phosphatidylinositol 3-kinase, wortmannin, and an inhibitor of actin cytoskeletal organization, cytochalasin D, blocked the bone-stimulated increase in Pi uptake. Phosphonoformic acid (PFA), an inhibitor of the renal NaPi-cotransporter, reduced NaPi uptake in the osteoclast, PFA also elicited a dose-dependent inhibition of bone resorption, PFA limited ATP production in osteoclasts attached to bone particles, Our results suggest that Pi transport in the osteoclast is a process critical to the resorption of bone through provision of necessary energy substrates.