Cluster formation of inositol 1,4,5-trisphosphate receptor requires its transition to open state
Cluster formation of inositol 1,4,5-trisphosphate receptor requires its transition to open state
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DOI：
10.1074/jbc.m405469200
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发表时间：
2005-02-25
影响因子：
4.8
通讯作者：
Mikoshiba, K
中科院分区：
文献类型：
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作者：
Tateishi, Y;Hattori, M;Mikoshiba, K
三磷酸肌醇（IP 3）受体（IPsR）Ca ~（2+）通道在生理和病理过程中起着重要作用。先前报道，当胞质Ca 2+浓度（[Ca 2 +]（C））升高时，IP 3R在内质网上形成簇。然而，IP，R聚类的分子机制在很大程度上仍然是未知的，因此其生理意义远不清楚。在这项研究中，我们发现由产生IP 3的激动剂诱发的绿色荧光蛋白标记的IP 3 R 1型（GFP-IP（3）R1）的聚集的时间过程与[Ca 2 +]（C）无关，但似乎与细胞质IP 3浓度相容。在[Ca 2 +]（C）没有显著增加的情况下，单独产生IP 3诱导GFP-Ip（3）R1聚集，但在没有IP 3产生的情况下，升高的[Ca 2 +]（C）不会。此外，IP（3）R1突变体不经历IP 3诱导的构象变化不能形成簇。因此，IP 3R成簇是由其IP 3诱导的构象变化到开放状态引起的。我们还发现GFP-Ip（3）R1簇与ERp 44共定位，ERp 44是一种抑制其通道活性的内质网腔蛋白。这是配体诱导的配体门控通道蛋白聚集的第一个例子。
The inositol 1,4,5-trisphosphate (IP3) receptor (IPsR) Ca2+ channel plays pivotal roles in many aspects of physiological and pathological events. It was previously reported that IP3R forms clusters on the endoplasmic reticulum when cytosolic Ca2+ concentration ([Ca2+](C)) is elevated. However, the molecular mechanism of IP,R clustering remains largely unknown, and thus its physiological significance is far from clear. In this study we found that the time course of clustering of green fluorescent protein-tagged IP3R type 1 (GFP-IP(3)R1), evoked by IP3-generating agonists, did not correlate with [Ca2+](C) but seemed compatible with cytoplasmic IP3 concentration. IP3 production alone induced GFP-Ip(3)R1 clustering in the absence of a significant increase in [Ca2+](C) but elevated [Ca2+](C) without IP3 production did not. Moreover IP(3)R1 mutants that do not undergo an IP3-induced conformational change failed to form clusters. Thus, IP3R clustering is induced by its IP3-induced conformational change to the open state. We also found that GFP-Ip(3)R1 clusters colocalized with ERp44, a luminal protein of endoplasmic reticulum that inhibits its channel activity. This is the first example of ligand-induced clustering of a ligand-gated channel protein.