title: The expression and function of cathepsin E in dendritic cells.
abstract: Cathepsin E is an aspartic proteinase that has been implicated in Ag processing within the class II MHC pathway. In this study, we document the presence of cathepsin E message and protein in human myeloid dendritic cells, the preeminent APCs of the immune system. Cathepsin E is found in a perinuclear compartment, which is likely to form part of the endoplasmic reticulum, and also a peripheral compartment just beneath the cell membrane, with a similar distribution to that of Texas Red-dextran within 2 min of endocytosis. To investigate the function of cathepsin E in processing, a new soluble targeted inhibitor was synthesized by linking the microbial aspartic proteinase inhibitor pepstatin to mannosylated BSA via a cleavable disulfide linker. This inhibitor was shown to block cathepsin D/E activity in cell-free assays and within dendritic cells. The inhibitor blocked the ability of dendritic cells from wild-type as well as cathepsin D-deficient mice to present intact OVA, but not an OVA-derived peptide, to cognate T cells. The data therefore support the hypothesis that cathepsin E has an important nonredundant role in the class II MHC Ag processing pathway within dendritic cells.
authors.affiliation: Department of Immunology and Molecular Pathology, University College London, London, United Kingdom. b.chain@ucl.ac.uk
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Chain
authors.forename: Paul
authors.initials: P
authors.lastname: Free
authors.forename: Patrick
authors.initials: P
authors.lastname: Medd
authors.forename: Claire
authors.initials: C
authors.lastname: Swetman
authors.forename: Alethea B
authors.initials: AB
authors.lastname: Tabor
authors.forename: Nadia
authors.initials: N
authors.lastname: Terrazzini
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000235:genetics; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors; D002402:Cathepsin D / Q000172:deficiency / Q000235:genetics; D020059:Cathepsin E / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology; D006801:Humans; D007424:Intracellular Fluid / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000276:immunology / Q000378:metabolism; D010436:Pepstatins / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism
chemical_list: D010436:Pepstatins; D012333:RNA, Messenger; D010047:Ovalbumin; D016282:Aspartic Acid Endopeptidases; D020059:Cathepsin E; D002402:Cathepsin D; C031375:pepstatin