Distinct subcellular localisations of the putative inositol 1,3,4,5-tetrakisphosphate receptors GAP1(IP4BP) and GAP1(m) result from the GAP1(IP4BP) PH domain directing plasma membrane targeting
Distinct subcellular localisations of the putative inositol 1,3,4,5-tetrakisphosphate receptors GAP1(IP4BP) and GAP1(m) result from the GAP1(IP4BP) PH domain directing plasma membrane targeting
复制标题
DOI：
10.1016/s0960-9822(06)00423-4
复制
发表时间：
1997-12-01
期刊：
影响因子：
9.2
通讯作者：
Cullen, PJ
中科院分区：
文献类型：
--
作者：
Lockyer, PJ;Bottomley, JR;Cullen, PJ
肌醇1，3，4，5-四磷酸肌醇(IP4)是一种普遍存在的肌醇磷酸酶，被认为具有第二信使的功能，最近我们纯化并克隆了一个可能的IF4受体，命名为Gap1(IP4BP)[1]，它也是GTP酶Ras家族Gap1激活蛋白家族的成员。Gap1(IP4BP)的同源物已被鉴定，称为Gap1(M)[2]，我们描述了从人循环血cDNA文库中克隆Gap1(M)的cDNA，我们发现Gap1(M)的一个缺失突变体与IP4结合，其亲和力和特异性与相应的Gap1(IP4BP)突变体相似，其中假定的磷脂结合结构域(C2a和C2b)已被去除。对这些蛋白在COS-7和HeLa细胞中的表达研究表明，Gap1(IP4BP)仅位于质膜上，而Gap1(M)似乎具有明显的核周定位。通过突变分析，我们发现这两个密切相关的蛋白质在亚细胞分布上的差异可能是它们各自的Pleckstrin同源(PH)结构域的函数，这种定位差异对于我们理解IP4的第二信使功能具有重要意义。
Inositol 1,3,4,5-tetrakisphosphate (IP4) is a ubiquitous inositol phosphate that has been suggested to function as a second messenger, Recently, we purified and cloned a putative IF4 receptor, termed GAP1(IP4BP) [1], which is also a member of the GAP1 family of GTPase-activating proteins for the Ras family of GTPases. A homologue of GAP1(IP4BP), called GAP1(m), has been identified [2] and here we describe the cloning of a GAP1(m) cDNA from a human circulating-blood cDNA library, We found that a deletion mutant of GAP1(m), in which the putative phospholipid-binding domains (C2A and C2B) have been removed, binds to IP4 with a similar affinity and specificity to that of the corresponding GAP1(IP4BP) mutant. Expression studies of the proteins in either COS-7 or HeLa cells showed that, whereas GAP1(IP4BP) is located solely at the plasma membrane, GAP1(m) seems to have a distinct perinuclear localisation, By mutational analysis, we have shown that the contrast in subcellular distribution of these two closely related proteins may be a function of their respective pleckstrin homology (PH) domains, This difference in localisation has fundamental significance for our understanding of the second messenger functions of IP4.