OSTEOCLAST REGULATION BY IONIZED CALCIUM

在骨吸收过程中，破骨细胞产生，因此， 暴露于毫摩尔 Ca2 水平。 本研究的目标 是定义细胞外 Ca2 变化的途径，以及 细胞内 Ca2 的相应变化，首先转导为 核内Ca2+的变化，然后导致基因的改变 表达。 值得注意的是，破骨细胞质膜代表了一种独特的 兰尼碱受体定位的位点。 瑞尼定受体是 Ca2 渗透通道通常存在于微粒体膜中。 然而，在破骨细胞中，一种质膜驻留的 II 型兰诺定 受体亚型用于感知细胞外 Ca2 的变化，因此 术语 Ca2 传感器。 最近的研究表明，兰尼碱受体 也位于核膜中，在该位置它们控制 Ca2_进入核质。 通过单独测量核 包膜和核质 Ca2 水平，以及通过执行共聚焦 使用表位特异性抗血清进行显微镜研究，我们首先建议 确定 Ca2 是否转运穿过破骨细胞核膜 通过兰尼碱受体门控 Ca2 通道发生。 此类研究是 特别与最近的观察结果相关，表明核 Ca2 水平直接调节基因表达。 因此，通过应用原位 逆转录酶聚合酶链反应 (RT=PCR) 分离 单个破骨细胞，我们建议研究 Ca2 是否调节 破骨细胞细胞因子 IL-6 基因的表达 与其受体一样。 最后，我们还将评估是否 分泌的白细胞介素 6 会减弱 Ca2 感应，我们认为这种现象 相信，应该允许吸收破骨细胞“逃脱”（或恢复） Ca2 诱导的抑制。 重要的治疗意义应该遵循 更好地理解细胞外 Ca2 的机制 破骨细胞中的Ca2+稳态的传感。

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.