Jeffries Tim R, Dove Stephen K, Michell Robert H, Parker Peter J
Protein Phosphorylation Laboratory, Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3PX, United Kingdom.
Mol Biol Cell. 2004 Jun;15(6):2652-63. doi: 10.1091/mbc.e03-10-0732. Epub 2004 Mar 12.
WIPI49 is a member of a previously undescribed family of WD40-repeat proteins that we demonstrate binds 3-phosphorylated phosphoinositides. Immunofluorescent imaging indicates that WIPI49 is localized to both trans-Golgi and endosomal membranes, organelles between which it traffics in a microtubule-dependent manner. Live cell imaging establishes that WIPI49 traffics through the same set of endosomal membranes as that followed by the mannose-6-phosphate receptor (MPR), and consistent with this, WIPI49 is enriched in clathrin-coated vesicles. Ectopic expression of wild-type WIPI49 disrupts the proper functioning of this MPR pathway, whereas expression of a double point mutant (R221,222AWIPI49) unable to bind phosphoinositides does not disrupt this pathway. Finally, suppression of WIPI49 expression through RNAi, demonstrates that its presence is required for normal endosomal organization and distribution of the CI-MPR. We conclude that WIPI49 is a novel regulatory component of the endosomal and MPR pathway and that this role is dependent upon the PI-binding properties of its WD40 domain.
WIPI49是WD40重复蛋白家族中一个此前未被描述的成员，我们证明它能结合3-磷酸化磷酸肌醇。免疫荧光成像表明，WIPI49定位于反式高尔基体和内体膜，它以微管依赖的方式在这些细胞器之间运输。活细胞成像证实，WIPI49与甘露糖-6-磷酸受体（MPR）通过同一组内体膜运输，与此一致的是，WIPI49在网格蛋白包被小泡中富集。野生型WIPI49的异位表达会破坏该MPR途径的正常功能，而无法结合磷酸肌醇的双点突变体（R221,222A WIPI49）的表达则不会破坏该途径。最后，通过RNA干扰抑制WIPI49的表达表明，其存在是内体正常组织和CI-MPR分布所必需的。我们得出结论，WIPI49是内体和MPR途径的一种新型调节成分，并且该作用依赖于其WD40结构域的PI结合特性。
