OSTEOCLAST REGULATION BY IONIZED CALCIUM

在骨吸收过程中，破骨细胞产生，因此， 就会暴露在毫摩尔浓度的钙离子中。 本研究的目的 是确定细胞外Ca 2+变化的途径， 细胞内Ca 2+的相应变化，首先被转导到 核内Ca 2+的变化，然后转化为基因的改变， 表情 值得注意的是，破骨细胞质膜代表了一种独特的 Ryanodine受体的位置。 Ryanodine受体 通常存在于微粒体膜中的Ca 2+渗透通道。 然而，在破骨细胞中，一种质膜驻留的II型兰尼碱， 受体亚型用于感知细胞外Ca 2+的变化，因此， 钙离子传感器。 最近的研究表明，兰尼碱受体 也位于核膜上，在那里它们控制着 Ca ~（2+）进入核质。 通过分别测量核 包膜和核质Ca 2+水平，以及通过进行共聚焦显微镜检查， 使用表位特异性抗血清的显微镜研究，我们首先提出， 确定Ca 2+是否穿过破骨细胞核膜 通过Ryanodine受体门控的Ca 2+通道发生。 此类研究 特别是最近的观察表明，核Ca 2 + 水平直接调节基因表达。 因此，通过在原位应用 逆转录聚合酶链反应（RT=PCR） 单个破骨细胞，我们建议研究是否钙调节 破骨细胞因子白细胞介素-6基因的表达，以及 与其受体相同。 最后，我们还将评估 分泌的白细胞介素-6减弱Ca 2+感应，这种现象，我们 我相信，应该允许再吸收破骨细胞“逃脱”（或恢复） Ca ~（2+）诱导的抑制。 重要的治疗意义应遵循 从更好地理解细胞外Ca 2+的机制 通过破骨细胞的感知和Ca 2+体内平衡。

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.