A ryanodine receptor-like molecule expressed in the osteoclast plasma membrane functions in extracellular Ca2+ sensing.
A ryanodine receptor-like molecule expressed in the osteoclast plasma membrane functions in extracellular Ca2+ sensing.
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DOI：
10.1172/jci118197
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发表时间：
1995-09
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影响因子：
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通讯作者：
M. Zaidi;V. Shankar;R. Tunwell;O. Adebanjo;J. Mackrill;M. Pazianas;D. O'Connell;B. Simon;B. Rifkin;A. Venkitaraman
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文献类型：
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作者：
M. Zaidi;V. Shankar;R. Tunwell;O. Adebanjo;J. Mackrill;M. Pazianas;D. O'Connell;B. Simon;B. Rifkin;A. Venkitaraman
Ryanodine受体(RyRs)存在于微粒体膜上，通过调节细胞内钙离子浓度的变化来调节细胞内钙离子的释放。在破骨细胞中，位于细胞质膜内的二价阳离子感受器钙离子受体(CAR)监测细胞外钙离子浓度的变化。在这里，我们证明了RyR样分子是该受体的一个功能成分。我们已经证明[~3H]ryanodine能与新鲜分离的大鼠破骨细胞特异性结合。该结合被ryanodine本身、CAR激动剂Ni2+和RyR拮抗剂Ru红所取代。后者还可抑制Ni2+诱导的细胞内钙离子升高。相反，对Ni2+的反应被提高到位于II型RyR通道形成区域内的表位的抗血清Ab129强烈增强。抗血清还对完整的、未固定的、台盼蓝阴性的破骨细胞表面进行染色。连续共聚焦切片和免疫金扫描电子显微镜证实了这种染色的质膜定位。针对细胞内RyR表位的抗血清Ab34意外地没有对活的破骨细胞染色，也没有增强CAR的激活。然而，它确实以一种独特的细胞质模式染色固定的、通透性的细胞。我们的结论是，RyR样分子存在于破骨细胞质膜中，在细胞外钙感应中发挥重要作用。
Ryanodine receptors (RyRs) reside in microsomal membranes where they gate Ca2+ release in response to changes in the cytosolic Ca2+ concentration. In the osteoclast, a divalent cation sensor, the Ca2+ receptor (CaR), located within the cell's plasma membrane, monitors changes in the extracellular Ca2+ concentration. Here we show that a RyR-like molecule is a functional component of this receptor. We have demonstrated that [3H] ryanodine specifically binds to freshly isolated rat osteoclasts. The binding was displaced by ryanodine itself, the CaR agonist Ni2+ and the RyR antagonist ruthenium red. The latter also inhibited cytosolic Ca2+ elevations induced by Ni2+. In contrast, the responses to Ni2+ were strongly potentiated by an antiserum Ab129 raised to an epitope located within the channel-forming domain of the type II RyR. The antiserum also stained the surface of intact, unfixed, trypan blue-negative osteoclasts. Serial confocal sections and immunogold scanning electron microscopy confirmed a plasma membrane localization of this staining. Antiserum Ab34 directed to a putatively intracellular RyR epitope expectedly did not stain live osteoclasts nor did it potentiate CaR activation. It did, however, stain fixed, permeabilized cells in a distinctive cytoplasmic pattern. We conclude that an RyR-like molecule resides within the osteoclast plasma membrane and plays in important role in extracellular Ca2+ sensing.