Roles of SAM and DDHD domains in mammalian intracellular phospholipase A₁ KIAA0725p

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• 作者：Hiroki Inoue¹ ; Takashi Baba¹ ; Seiichi Sato ; Ryuya Ohtsuki ; Aya Takemori ; Takuya Watanabe ; Mitsuo Tagaya ; Katsuko Tani ; ^{tani@toyaku.ac.jp}
• 关键词：DOPA ; 1 ; 2-dioleoyl-sn-phosphatidic acid ; ER ; endoplasmic reticulum ; ERGIC ; endoplasmic reticulum-Golgi intermediate compartment ; GST ; glutathione-S-transferase ; iPLA1 ; intracellular phospholipase A1 ; LPA ; 1-oleoyl-lysophosphatidic acid ; LUV ; large unilame
• 刊名：Biochimica et Biophysica Acta (BBA)/Molecular Cell Research
• 出版年：2012
• 期刊代码：20_01674889
• 类别：bio
• 出版时间：April, 2012
• 卷：1823
• 期：4
• 页码：930-939
• 文件大小：1373 K

摘要

Members of the intracellular phospholipase A₁ family of proteins have been implicated in organelle biogenesis and membrane trafficking. The mammalian family comprises three members: phosphatidic acid-preferring phospholipase A₁ (PA-PLA₁)/DDHD1, p125/Sec23ip and KIAA0725p/DDHD2, all of which have a DDHD domain. PA-PLA₁ 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-PLA₁. 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.