Trafficking of prion proteins through a caveolae-mediated endosomal pathway.
To understand the posttranslational conversion of the cellular prion protein (PrPC) to its pathologic conformation, it is important to define the intracellular trafficking pathway of PrPC within the endomembrane system. We studied the localization and internalization of PrPC in CHO cells using cryoimmunogold electron microscopy. At steady state, PrPC was enriched in caveolae both at the TGN and plasma membrane and in interconnecting chains of endocytic caveolae. Protein A-gold particles bound specifically to PrPC on live cells. These complexes were delivered via caveolae to the pericentriolar region and via nonclassical, caveolae-containing early endocytic structures to late endosomes/lysosomes, thereby bypassing the internalization pathway mediated by clathrin-coated vesicles. Endocytosed PrPC-containing caveolae were not directed to the ER and Golgi complex. Uptake of caveolae and degradation of PrPC was slow and sensitive to filipin. This caveolae-dependent endocytic pathway was not observed for several other glycosylphosphatidyl inositol (GPI)-anchored proteins. We propose that this nonclassical endocytic pathway is likely to determine the subcellular location of PrPC conversion.
Peters
Peter J
PJ
Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Plesmanlaan 121-H4, 1066 CX Amsterdam, The Netherlands. p.peters@nki.nl
Mironov
Alexander
A
Peretz
David
D
van Donselaar
Elly
E
Leclerc
Estelle
E
Erpel
Susanne
S
DeArmond
Stephen J
SJ
Burton
Dennis R
DR
Williamson
R Anthony
RA
Vey
Martin
M
Prusiner
Stanley B
SB
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D016466:CHO Cells; D021941:Caveolae / Q000378:metabolism* / Q000648:ultrastructure; D051242:Caveolin 1; D022461:Caveolins / Q000096:biosynthesis / Q000235:genetics; D006224:Cricetinae; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D017979:Gold Colloid / Q000378:metabolism; D008854:Microscopy, Electron; D011328:Prions / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D011990:Receptors, Transferrin / Q000378:metabolism
D001426:Bacterial Proteins; D051242:Caveolin 1; D022461:Caveolins; D017979:Gold Colloid; D011328:Prions; D011990:Receptors, Transferrin; C070001:protein AG-gold complex