HETEROTETRAMERIC COMPLEX-FORMATION OF INOSITOL 1,4,5-TRISPHOSPHATE RECEPTOR SUBUNITS
HETEROTETRAMERIC COMPLEX-FORMATION OF INOSITOL 1,4,5-TRISPHOSPHATE RECEPTOR SUBUNITS
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DOI：
10.1074/jbc.270.24.14700
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发表时间：
1995-06-16
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：
MONKAWA, T;MIYAWAKI, A;MIKOSHIBA, K
肌醇1,4,5-三磷酸受体（IP(3)R）以四聚体复合物形式存在，形成功能性肌醇1,4,5-三磷酸门控Ca2+通道。分子克隆研究表明，至少有三种类型的IP(3)R亚基，指定为1型，2型和3型。采用Western blot分析，利用针对IP(3)R亚基的15个c端氨基酸的型特异性抗体，研究了IP(3)R亚基在不同细胞系中的表达水平。我们发现所有三种类型的IP(3)R亚基在每个细胞系中都有表达，但它们的表达水平不同。为了确定IP(3)Rs是否形成异源四聚体，我们使用中国仓鼠卵巢细胞（CHO-K1细胞）进行了免疫沉淀实验，这三种类型的细胞都大量表达。每种类型特异性抗体不仅免疫沉淀各自的同源型，而且免疫沉淀其他两种类型。这一结果表明不同类型的IP(3)R亚基在CHO-K1细胞中聚集形成异源四聚体。我们还在大鼠肝脏中检测到异源四聚体，其中IP(3)R 1型和2型大量表达。先前的研究表明IP(3)R类型之间存在一定的功能差异，这表明不同亚基组成可能具有不同的通道特性。不同的IP(3)R亚基的共组装可以进一步增加IP(3)R通道的多样性，形成原生或异源四聚体。
The inositol 1,4,5-trisphosphate receptor (IP(3)R) exists as a tetrameric complex to form a functional inositol 1,4,5-trisphosphate-gated Ca2+ channel. Molecular cloning studies have shown that there are at least three types of IP(3)R subunits, designated type 1, type 2, and type 3. The levels of expression of IP(3)R subunits in various cell lines were investigated by Western blot analysis using type-specific antibodies against 15 C-terminal amino acids of each IP(3)R subunit. We found that all the three types of IP(3)R subunits were expressed in each cell line examined, but their levels of expression varied. To determine whether IP(3)Rs form heterotetramers, we employed immunoprecipitation experiments using Chinese hamster ovary cells (CHO-K1 cells), in which all three types are abundantly expressed. Each type-specific antibody immunoprecipitated not only the respective cognate type but also the other two types. This result suggests that distinct types of IP(3)R subunits assemble to form heterotetramers in CHO-K1 cells. We also detected heterotetramers in rat liver, in which IP(3)R type 1 and type 2 are expressed abundantly. Previous studies have shown some functional differences among IP(3)R types, suggesting the possibility that various compositions of subunits show distinct channel properties. The diversity of IP(3)R channels may be further increased by the co-assembly of different IP(3)R subunits to form home- or heterotetramers.