Fatty acid remodeling of GPI-anchored proteins is required for their raft association.
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.
Maeda
Yusuke
Y
Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan.
Tashima
Yuko
Y
Houjou
Toshiaki
T
Fujita
Morihisa
M
Yoko-o
Takehiko
T
Jigami
Yoshifumi
Y
Taguchi
Ryo
R
Kinoshita
Taroh
T
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*
D005227:Fatty Acids; D017261:Glycosylphosphatidylinositols; D010744:Phosphoric Monoester Hydrolases