The Expression and Function of Cathepsin E in Dendritic Cells

• Published in: The Journal of immunology (1950) Vol. 174; no. 4; pp. 1791 - 1800
• Main Authors: Chain, Benjamin M, Free, Paul, Medd, Patrick, Swetman, Claire, Tabor, Alethea B, Terrazzini, Nadia
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 15-02-2005
• Subjects: Animals; Antigen Presentation - genetics; Aspartic Acid Endopeptidases - antagonists & inhibitors; Cathepsin D - deficiency; Cathepsin D - genetics; Cathepsin E - biosynthesis; Cathepsin E - genetics; Cathepsin E - metabolism; Cathepsin E - physiology; Cells, Cultured; Dendritic Cells - enzymology; Dendritic Cells - immunology; Dendritic Cells - metabolism; Down-Regulation - genetics; Down-Regulation - immunology; Humans; Intracellular Fluid - enzymology; Intracellular Fluid - metabolism; Mice; Mice, Inbred BALB C; Mice, Knockout; Mice, Transgenic; Ovalbumin - immunology; Ovalbumin - metabolism; Pepstatins - pharmacology; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; T-Lymphocytes - immunology; T-Lymphocytes - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.174.4.1791

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.