Abstract
Class II MHC molecules survey the endocytic compartments of APCs and present antigenic peptides to CD4 T cells. In this context, lysosomal proteases are essential not only for the generation of antigenic peptides but also for proteolysis of the invariant chain to allow the maturation of class II MHC molecules. Recent studies with protease inhibitors have implicated the asparagine endopeptidase (AEP) in class II MHC-restricted Ag presentation. We now report that AEP-deficient mice show no differences in processing of the invariant chain or maturation of class II MHC products compared with wild-type mice. In the absence of AEP, presentation to primary T cells of OVA and myelin oligodendrocyte glycoprotein, two Ags that contain asparagine residues within or in proximity to the relevant epitopes was unimpaired. Cathepsin (Cat) L, a lysosomal cysteine protease essential for the development to CD4 and NK T cells, fails to be processed into its mature two-chain form in AEP-deficient cells. Despite this, the numbers of CD4 and NK T cells are normal, showing that the single-chain form of Cat L is sufficient for its function in vivo. We conclude that AEP is essential for processing of Cat L but not for class II MHC-restricted Ag presentation.
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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Antigen Presentation / genetics
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Antigen Presentation / immunology*
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Antigen-Presenting Cells / enzymology*
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Antigen-Presenting Cells / immunology
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Antigen-Presenting Cells / metabolism
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Antigens, Differentiation, B-Lymphocyte / immunology
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Antigens, Differentiation, B-Lymphocyte / metabolism
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CD4-Positive T-Lymphocytes / cytology
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CD4-Positive T-Lymphocytes / enzymology
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Cathepsin L
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Cathepsins / deficiency
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Cathepsins / genetics
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Cathepsins / metabolism*
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Cell Differentiation / genetics
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Cell Differentiation / immunology
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Cysteine Endopeptidases / deficiency
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Cysteine Endopeptidases / genetics
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Cysteine Endopeptidases / metabolism*
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Cysteine Endopeptidases / physiology*
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Histocompatibility Antigens Class II / genetics
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Histocompatibility Antigens Class II / immunology*
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Histocompatibility Antigens Class II / metabolism*
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Isoenzymes / deficiency
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Isoenzymes / metabolism
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Killer Cells, Natural / cytology
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Killer Cells, Natural / enzymology
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Mice, Transgenic
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Myelin Proteins
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Myelin-Associated Glycoprotein / immunology
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Myelin-Associated Glycoprotein / metabolism
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Myelin-Oligodendrocyte Glycoprotein
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Ovalbumin / immunology
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Ovalbumin / metabolism
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Protein Processing, Post-Translational / genetics
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Protein Processing, Post-Translational / immunology*
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T-Lymphocyte Subsets / cytology
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T-Lymphocyte Subsets / enzymology
Substances
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Antigens, Differentiation, B-Lymphocyte
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Histocompatibility Antigens Class II
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Isoenzymes
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Mog protein, mouse
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Myelin Proteins
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Myelin-Associated Glycoprotein
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Myelin-Oligodendrocyte Glycoprotein
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invariant chain
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Ovalbumin
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Cathepsins
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Cysteine Endopeptidases
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Cathepsin L
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Ctsl protein, mouse
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asparaginylendopeptidase