An AP-1/clathrin coat plays a novel and essential role in forming the Weibel-Palade bodies of endothelial cells.
Clathrin provides an external scaffold to form small 50-100-nm transport vesicles. In contrast, formation of much larger dense-cored secretory granules is driven by selective aggregation of internal cargo at the trans-Golgi network; the only known role of clathrin in dense-cored secretory granules formation is to remove missorted proteins by small, coated vesicles during maturation of these spherical organelles. The formation of Weibel-Palade bodies (WPBs) is also cargo driven, but these are cigar-shaped organelles up to 5 mum long. We hypothesized that a cytoplasmic coat might be required to make these very different structures, and we found that new and forming WPBs are extensively, sometimes completely, coated. Overexpression of an AP-180 truncation mutant that prevents clathrin coat formation or reduced AP-1 expression by small interfering RNA both block WPB formation. We propose that, in contrast to other secretory granules, cargo aggregation alone is not sufficient to form immature WPBs and that an external scaffold that contains AP-1 and clathrin is essential.
Lui-Roberts
Winnie W Y
WW
Medical Research Council Laboratory of Molecular Cell Biology, Cell Biology Unit and Department of Biochemistry and Molecular Biology, University College London, London, England, UK.
Collinson
Lucy M
LM
Hewlett
Lindsay J
LJ
Michaux
Grégoire
G
Cutler
Daniel F
DF
D033961:Adaptor Protein Complex 1 / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002966:Clathrin / Q000378:metabolism; D022163:Clathrin-Coated Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D045683:Furin / Q000378:metabolism; D006801:Humans; D021381:Protein Transport / Q000187:drug effects; D034622:RNA Interference; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014470:Umbilical Cord / Q000166:cytology / Q000648:ultrastructure; D020302:Weibel-Palade Bodies / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D021601:trans-Golgi Network / Q000187:drug effects / Q000378:metabolism; D014841:von Willebrand Factor / Q000378:metabolism
D033961:Adaptor Protein Complex 1; D002966:Clathrin; D014841:von Willebrand Factor; D045683:Furin; D013755:Tetradecanoylphorbol Acetate