Roles of SAM and DDHD domains in mammalian intracellular phospholipase A1 KIAA0725p
Roles of SAM and DDHD domains in mammalian intracellular phospholipase A1 KIAA0725p
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DOI：
10.1016/j.bbamcr.2012.02.002
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发表时间：
2012-04-01
影响因子：
5.1
通讯作者：
Tani, Katsuko
中科院分区：
文献类型：
--
作者：
Inoue, Hiroki;Baba, Takashi;Tani, Katsuko
细胞内磷脂酶A（1）蛋白家族的成员与细胞器的生物发生和膜运输有关。哺乳动物家族包括三个成员：磷脂酸偏好型磷脂酶A（1）（PA-PLA（1））/DDHD 1、p125/Sec 23 ip和KIAA 0725 p/DDHD 2，它们都具有DDHD结构域。PA-PLA（1）主要是胞质的，而KIAA 0725 p和p125分别与高尔基体/内质网（ER）-高尔基体中间室（ERGIC）和ER出口位点更稳定地结合。在这里，我们表明，KIAA 0725 p和p125是新的磷酸肌醇结合蛋白。KIAA 0725 p的缺失和突变分析表明，p125中也存在但不存在于胞质PA-PLA 1中的无菌α基序（SAM）和随后的DDHD结构域包含磷脂酰肌醇4-磷酸（PI（4）P）结合的最小区域。在SAM结构域的带正电荷簇中具有突变的构建体在磷酸肌醇结合和高尔基体/ERGIC靶向方面都有缺陷。与PI（4）P结合对KIAA 0725 p的膜结合很重要的观点一致，磷酸肌醇磷酸酶Sac 1的表达减少了表达的KIAA 0725 p与膜的结合。此外，我们发现DDHD结构域的缺失或在该结构域中保守的天冬氨酸或组氨酸残基处引入点突变会消除KIAA 0725 p和PA-PLA的磷脂酶活性（1）。总之，我们的研究结果表明，KIAA 0725 p是针对特定的细胞器膜的磷酸肌醇依赖性的方式，其SAM和DDHD结构域是必不可少的磷酸肌醇结合和磷脂酶活性。(c)2012爱思唯尔有限公司版权所有。
Members of the intracellular phospholipase A(1) family of proteins have been implicated in organelle biogenesis and membrane trafficking. The mammalian family comprises three members: phosphatidic acid-preferring phospholipase A(1) (PA-PLA(1))/DDHD1, p125/Sec23ip and KIAA0725p/DDHD2, all of which have a DDHD domain. PA-PLA(1) is mostly cytosolic, while KIAA0725p and p125 are more stably associated with the Golgi/endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC) and ER exit sites, respectively. Here we show that KIAA0725p and p125 are novel phosphoinositide-binding proteins. Deletion and mutational analyses of KIAA0725p suggested that a sterile alpha-motif (SAM), which is also present in p125, but not in cytosolic PA-PLA1, and the following DDHD domain comprise a minimal region for phosphatidylinositol 4-phosphate (PI(4)P)-binding. A construct with mutations in the positively charged cluster of the SAM domain is defective in both phosphoinositide-binding and Golgi/ERGIC targeting. Consistent with the view that the PI(4)P-binding is important for the membrane association of KIAA0725p, expression of phosphoinositide phosphatase Sac1 reduces the association of expressed KIAA0725p with membranes. In addition, we show that deletion of the DDHD domain or introduction of point mutations at the conserved aspartate or histidine residues in the domain abolishes the phospholipase activity of KIAA0725p and PA-PLA(1). Together, our results suggest that KIAA0725p is targeted to specific organelle membranes in a phosphoinositide-dependent manner, and that its SAM and DDHD domains are essential for its phosphoinositide-binding and phospholipase activity. (c) 2012 Elsevier B.V. All rights reserved.