标题: Sorting it out, without clathrin [打印本页] 作者: 杨柳 时间: 2009-3-6 00:13 标题: Sorting it out, without clathrin
Nichols/Macmillan $ x# X( V& r% z2 }, r5 s( [/ D. M3 S- v! ~- Q. P
Clathrin-independent endocytosis is revealing itself at last. Intermediary organelles in this pathway have been difficult to identify, due in part to a dearth of markers and, until recently, difficulties in blocking the clathrin-dependent process. But now, Benjamin Nichols (MRC Laboratory of Molecular Biology, Cambridge, UK) has identified a set of endosomes that are uniquely involved in clathrin-independent trafficking.Nichols' results demonstrate that vesicles containing caveolin-1 define a set of early endosomes that are distinct from those that form from clathrin-coated pits. Proteins that were endocytosed independently of clathrin, including GPI-anchored proteins and the cholera toxin B subunit, were found within the caveolin-1–positive endosomes. Even in the absence of clathrin-mediated endocytosis, these proteins were delivered from the plasma membrane to the Golgi. % n1 r4 Z. E, o4 ~8 Y7 l F0 X3 }( I: d1 |/ x! P$ l
Although caveolin-1 provides a useful marker for the pathway, the protein was not important for endocytosis. Nichols found that caveolin-1 was sorted away from Golgi-bound vesicles, and diminished caveolin-1 levels did not inhibit clathrin-independent endocytosis. Caveolin-1–containing endosomes have previously been shown to transport SV40 virus to the ER. Nichols believes these may be the same organelles, although this is not yet proven. 5 \5 I3 i& f8 l/ a " o3 M/ i1 B( F0 B" a- mThe function of the clathrin-independent pathway will be better understood when specific inhibitors can be identified. For now, Nichols hypothesizes that clathrin-independent endocytosis is important for delivery of certain plasma membrane lipids to the trans face of the Golgi, the site of lipid raft formation and Golgi cargo sorting. + F' d* C: y8 H$ f( e8 Y Y7 \ g- Z
Reference: , l( l$ Q. M1 v( |( ]" W, I$ u% P; w6 U 5 o2 J: V5 e) C1 Y9 D% q% YNichols, B. 2002. Nat. Cell Biol. 10.1038/ncb787.(Caveolin-1 (green) endosomes carry cargo)作者: 兔兔 时间: 2015-6-10 20:54