Fatty acid remodeling of GPI-anchored proteins is required for their raft association
Fatty acid remodeling of GPI-anchored proteins is required for their raft association
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DOI：
10.1091/mbc.e06-10-0885
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发表时间：
2007-04-01
影响因子：
3.3
通讯作者：
Kinoshita, Taroh
中科院分区：
文献类型：
--
作者：
Maeda, Yusuke;Tashima, Yuko;Kinoshita, Taroh
尽管大多数细胞磷脂酰肌醇（PI）含有不饱和脂肪链并且被排除在筏之外，但GPI锚定蛋白（AP）在其PI部分中不寻常地含有两个饱和脂肪链，并且它们通常在脂筏内发现。然而，饱和链的起源以及它们是否是筏协会所必需的尚不清楚。在这里，我们报告说，GPI-AP，有两个饱和脂肪链，是从那些轴承不饱和链脂肪酸重塑，最有可能发生在高尔基体，需要后GPI附着蛋白质（PGAP）2和PGAP 3。从PGAP 2和-3双突变体中国仓鼠卵巢（CHO）细胞分离的表面GPI-AP具有不饱和链，如sn-2位的油酸、花生四烯酸和二十二碳四烯酸，而来自野生型CHO细胞的GPI-AP仅具有饱和链硬脂酸，表明sn-2链被交换为饱和链。然后，我们评估了GPI-AP与脂筏的关联。在洗涤剂抗性膜组分中，来自双突变细胞的未重塑GPI-AP的回收率非常低，表明GPI-AP能够通过PGAP 3和PGAP 2介导的脂肪酸重塑并入脂筏。我们还表明，重塑需要前PGAP 1介导的去酰化从肌醇GPI-AP在内质网。
Whereas most of the cellular phosphatidylinositol (PI) contain unsaturated fatty chains and are excluded from rafts, GPI-anchored proteins (APs) unusually contain two saturated fatty chains in their PI moiety, and they are typically found within lipid rafts. However, the origin of the saturated chains and whether they are essential for raft association are unclear. Here, we report that GPI-APs, with two saturated fatty chains, are generated from those bearing an unsaturated chain by fatty acid remodeling that occurs most likely in the Golgi and requires post-GPI-attachment to proteins (PGAP)2 and PGAP3. The surface GPI-APs isolated from the PGAP2 and -3 double-mutant Chinese hamster ovary (CHO) cells had unsaturated chains, such as oleic, arachidonic, and docosatetraenoic acids in the sn-2 position, whereas those from wild-type CHO cells had exclusively stearic acid, a saturated chain, indicating that the sn-2 chain is exchanged to a saturated chain. We then assessed the association of GPI-APs with lipid rafts. Recovery of unremodeled GPI-APs from the double-mutant cells in the detergent-resistant membrane fraction was very low, indicating that GPI-APs become competent to be incorporated into lipid rafts by PGAP3- and PGAP2-mediated fatty acid remodeling. We also show that the remodeling requires the preceding PGAP1-mediated deacylation from inositol of GPI-APs in the endoplasmic reticulum.