Modulation of Ca2+ entry by polypeptides of the inositol 1,4,5-trisphosphate receptor (IP3R) that bind transient receptor potential (TRP):: Evidence for roles of TRP and IP3R in store depletion-activated Ca2+ entry
Modulation of Ca2+ entry by polypeptides of the inositol 1,4,5-trisphosphate receptor (IP3R) that bind transient receptor potential (TRP):: Evidence for roles of TRP and IP3R in store depletion-activated Ca2+ entry
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DOI：
10.1073/pnas.96.26.14955
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发表时间：
1999-12-21
影响因子：
11.1
通讯作者：
Birnbaumer, L
中科院分区：
文献类型：
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作者：
Boulay, G;Brown, DM;Birnbaumer, L
果蝇瞬时受体电位 (TRP) 的同源物被认为是质膜离子通道的单一亚基，由于主动或被动消耗 Ca2+ 储备而被激活。与这一假设一致的是，表达 TRP 的细胞显示出新型 Ca2+ 渗透性阳离子通道，该通道可以被肌醇 1,4,5-三磷酸受体 (IP3R) 蛋白激活。 TRP 的表达以多种方式改变细胞，包括上调非 TRP 基因编码的 IP3R，并且仍然缺乏 TRP 形成这些细胞和其他细胞通道的证据。在这里，我们通过免疫共沉淀和谷胱甘肽 S-转移酶下拉实验记录了 TRP 和 IP3R 的物理相互作用，并鉴定了 IP3R F2q 和 F2g 的两个区域，它们与 TRP C7 的一个区域相互作用。这些相互作用区域在具有未修饰的 TRP 和 IP3R 补体的细胞中表达，以研究它们对激动剂以及储存耗尽诱导的 Ca2+ 进入的影响，并测试它们各自的结合配偶体在 Ca2+ 进入中的作用。 C7 和包含 F2q 的 IP3R 片段减少了两种形式的 Ca2+ 内流。相比之下，F2g 增强了两种形式的 Ca2+ 进入。我们得出的结论是，储存耗尽激活的 Ca2+ 进入是通过以 TRP 作为其正常结构成分之一的通道发生的，并且这些通道直接由 IP3R 激活。因此，IP3R 具有双重作用：从储存中释放 Ca2+ 并响应于 IP3 增加或管腔 Ca2+ 减少而激活 Ca2+ 内流。
Homologues of Drosophilia transient receptor potential (TRP) have been proposed to be unitary subunits of plasma membrane ion channels that are activated as a consequence of active or passive depletion of Ca2+ stores. In agreement with this hypothesis, cells expressing TRPs display novel Ca2+-permeable cation channels that can be activated by the inositol 1,4,5-trisphosphate receptor (IP3R) protein. Expression of TRPs alters cells in many ways, including up-regulation of IP3Rs not coded for by TRP genes, and proof that TRP forms channels of these and other cells is still missing. Here, we document physical interaction of TRP and IP3R by coimmunoprecipitation and glutathione S-transferase-pulldown experiments and identify two regions of IP3R, F2q and F2g, that interact with one region of TRP, C7. These interacting regions were expressed in cells with an unmodified complement of TRPs and IP3Rs to study their effect on agonist- as well as store depletion-induced Ca2+ entry and to test for a role of their respective binding partners in Ca2+ entry. C7 and an F2q-containing fragment of IP3R decreased both forms of Ca2+ entry. In contrast, F2g enhanced the two forms of Ca2+ entry. We conclude that store depletion-activated Ca2+ entry occurs through channels that have TRPs as one of their normal structural components, and that these channels are directly activated by IP3Rs. IP3Rs, therefore, have the dual role of releasing Ca2+ from stores and activating Ca2+ influx in response to either increasing IP3 or decreasing luminal Ca2+.