Abstract
The invariant chain (Ii) is a chaperone that regulates assembly and transport of class II MHC molecules. In the absence of the lysosomal protease cathepsin S (CatS), degradation of Ii is impaired and an Ii remnant that extends from the N terminus to about residue 110 accumulates in class II MHC-positive endosomal compartments, which are enlarged in size and lack multivesicular morphology. In primary B cells examined in vitro and in lymph nodes examined by immuno-electron microscopy, CatS controls architecture of class II-positive endosomal compartments. In a compound mutant mouse that lacks both CatS and Ii, the normal size of endosomes in class II-positive cells is restored, although internal endosomal membranes are absent. Proper degradation of Ii is thus essential for normal endosomal morphology in antigen-presenting cells in vivo.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Antigens, Differentiation, B-Lymphocyte / immunology*
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B-Lymphocytes / cytology
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B-Lymphocytes / immunology
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Cathepsins / deficiency
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Cathepsins / immunology*
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Cell Compartmentation / immunology
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Endosomes / enzymology*
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Endosomes / immunology*
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Endosomes / ultrastructure
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Histocompatibility Antigens Class II / biosynthesis
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Histocompatibility Antigens Class II / immunology*
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Lipopolysaccharides / immunology
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Lipopolysaccharides / pharmacology
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Lymph Nodes / immunology
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Mice
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Mice, Knockout
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Microscopy, Confocal
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Microscopy, Electron, Transmission
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Specific Pathogen-Free Organisms
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Spleen / cytology
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Spleen / immunology
Substances
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Antigens, Differentiation, B-Lymphocyte
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Histocompatibility Antigens Class II
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Lipopolysaccharides
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invariant chain
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Cathepsins
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cathepsin S