REGULATION OF PHOSPHATE TRANSPORT IN THE OSTEOCLAST

描述(改编自申请人的摘要)：磷酸盐(PI)是 矿化骨基质的碱性阴离子成分，主要是 羟基磷灰石。在骨吸收过程中，破骨细胞暴露在高剂量下。 通过骨基质脱矿释放的PI浓度。 因此，可以想象破骨细胞具有特定的运输能力。 细胞内游离PI池摄取PI的机制。此外， PI转运可能与维持脑组织中的ATP含量有关 破骨细胞在迁移、附着和循环过程中的作用 再吸收。在本申请中，首席调查员建议 纳皮转运蛋白的活性在维持 破骨细胞所需能量所需的底物水平。 申请人有证据表明钠依赖的PI共转运体在 破骨细胞定位在一个循环的内体池中，该池迅速 当与骨骼接触时，重新分布到质膜。的目标是 这项提议是为了回答在 钠依赖磷酸(Napi)共转运蛋白的初步研究 在破骨细胞中。这些包括：(1)什么是分子鉴定 破骨细胞中的纳皮转运蛋白；(2)破骨细胞的性质是什么？ 回收含有Napi共转运蛋白的内体池；3)什么是 破骨细胞附着在骨骼上所引发的信号，导致 刺激PI的摄取；以及(4) NA：PI-共转运体至正常破骨细胞功能。为了解决这些问题， 本申请的具体目的是：(1)确定分子 破骨细胞中Napi转运蛋白的鉴定；申请人 假设它与肾脏的Napi-2亚型有关，但不完全相同 (2)确定泡囊的作用机制。 破骨细胞中纳皮转运蛋白的运输。申请者将会 关注触发刺激的初始信号通路 Napi共转运蛋白的反应和差异靶向；以及(3)到 确定napi转运蛋白在正常破骨细胞功能中的作用。 申请人提出，磷酸盐运输是一个关键的过程 破骨细胞功能正常。“敲除”功能的功效和 Napi共转运蛋白的表达将在体外和在 活着。申请人建议，国家适应行动方案中的联合转运体 破骨细胞可能为新的治疗提供潜在的靶点 治疗骨质疏松症的干预措施。

DESCRIPTION (Adapted from the Applicant's Abstract): Phosphate (Pi) is the basic anionic component of the mineralized bone matrix, which is primarily hydroxyapatite. During bone resorption, the osteoclast is exposed to high concentrations of Pi released through demineralization of the bone matrix. Therefore, it is conceivable that the osteoclasts possess specific transport mechanisms for Pi uptake into the intracellular free Pi pool. Furthermore, Pi transport may be linked to maintenance of the ATP content of the osteoclast during the cyclical processes of migration, attachment and resorption. In this application, the principal investigator proposes that the activity of a NaPi-cotransporter plays a key role in maintaining substrate levels necessary for the energy requirements of the osteoclast. The applicant has evidence that the Na-dependent Pi cotransporter in the osteoclast localizes within a recycling endosomal pool which rapidly redistributes to the plasma membrane upon contact with bone. The goal of this proposal is to answer several questions which have arisen during the initial characterization of the Na-dependent phosphate (NaPi)-cotransporter in the osteoclast. These include: (1) what is the molecular identify of the NaPi-cotransporter in the osteoclast; (2) what is the nature of the recycling endosomal pool which contains the NaPi cotransporter; 3) what are the signals initiated by the attachment of osteoclasts to bone, leading to stimulation of Pi uptake; and (4) what is the contribution of the Na:Pi-cotransporter to normal osteoclast function. To address these issues, the Specific Aims of this application are: (1) to determine the molecular identify of the NaPi-cotransporter in the osteoclast; the applicant postulates that it is related, but not identical to the renal NaPi-2 isoform (rat, Type II family); (2) to determine the mechanisms of vesicular trafficking of the NaPi-cotransporter in the osteoclast. The applicant will focus on the initial signaling pathways which trigger the stimulatory responses and differential targeting of the NaPi-cotransporter; and (3) to determine the role of the NaPi-cotransporter in normal osteoclast function. The applicant proposes that phosphate transport is a process critical to normal osteoclast function. The efficacy of "knocking out" the function and expression of the NaPi-cotransporter will be assessed, both in vitro and in vivo. It is suggested by the applicant that the NaPi-cotransporter in the osteoclast may provide a potential target for novel therapeutic interventions in the treatment of osteoporosis.