OSTEOCLAST REGULATION BY IONIZED CALCIUM

在骨吸收过程中，破骨细胞产生，因此， 暴露在毫米级的钙离子水平下。本研究的目的是 是定义细胞外钙变化的途径，以及 细胞内钙离子的相应变化首先被转导到 核内钙离子的变化，进而转化为基因的变化 表情。值得注意的是，破骨细胞质膜代表一种独特的 兰尼定受体的位置。兰尼定受体是 通常存在于微粒体膜中的钙离子通透通道。 然而，在破骨细胞中，一种驻留在质膜上的II型兰诺定 受体亚型用于感知细胞外钙的变化，因此 术语钙传感器。最近的研究表明，兰尼定受体是 也位于核膜上，它们在哪个部位门的流量 Ca2_2进入核质。通过对原子核进行单独测量 包膜和核质钙水平，以及通过执行共聚焦 利用表位特异性抗血清进行显微研究，我们首次提出 测定钙离子是否通过破骨细胞核膜转运 通过兰诺定受体门控的钙通道发生。这类研究是 尤其与最近的观察结果有关，这些观察表明，核钙离子 水平直接调节基因的表达。因此，通过将现场应用于 逆转录-聚合酶链式反应(RT=PCR)检测分离株 单个破骨细胞，我们建议研究钙是否调节 破骨细胞细胞因子白介素6基因的表达 和它的受体一样。最后，我们还将评估是否 分泌的白介素6减弱了对钙的感知，这是一种现象，我们 相信，应该允许吸收的破骨细胞从 Ca2诱导的抑制作用。重要的治疗意义应遵循 通过更好地理解细胞外钙离子的机制 通过破骨细胞感知，以及破骨细胞内的钙稳态。

During bone resorption, an osteoclast generates and, as a consequence, becomes exposed to millimolar Ca2+ levels. The goal of the present study is to define pathways through which changes in extracellular Ca2+, and corresponding changes in intracellular Ca2+, are transduced first into changes in intranuclear Ca2+, and then into alterations in gene expression. Notably, the osteoclast plasma membrane represents a unique site for the location of a ryanodine receptor. Ryanodine receptors are Ca2+-permeable channels that normally reside in microsomal membranes. However, in the osteoclast, a plasma membrane-resident, type II, ryanodine receptor isoform serves to sense changes in extracellular Ca2+, hence the term Ca2+ sensor. It has been shown recently that ryanodine receptors are also located in nuclear membranes at which site they gate the flux of Ca2_+ into the nucleoplasm. By making separate measurement of nuclear envelope and nucleoplasmic Ca2+ levels, as well as by performing confocal microscopic studies using epitope-specific antisera, we first propose to determine whether Ca2+ transport across the osteoclast nuclear membrane occurs through ryanodine receptor-gated Ca2+ channels. Such studies are particularly relevant to recent observations showing that nuclear Ca2+ levels regulate gene expression directly. Thus, by applying the in situ reverse transcriptase polymerase chain reaction (RT=PCR) to isolated single osteoclasts, we propose to investigate whether Ca2+ modulates expression of the gene for the osteoclast cytokine, interleukin-6, as well as that of its receptor. Finally, we will also assess whether the secreted interleukin-6 attenuates Ca2+ sensing, a phenomenon that, we believe, should allow a resorbing osteoclast 'escape' (or recover) from Ca2+-induced inhibition. Important therapeutic implications should follow from a better understanding of mechanisms that underlie extracellular Ca2+ sensing by, and Ca2+ homeostasis in, the osteoclast.