Critical Role for Asparagine Endopeptidase in Endocytic Toll-like Receptor Signaling in Dendritic Cells

• Published in: Immunity (Cambridge, Mass.) Vol. 31; no. 5; pp. 737 - 748
• Main Authors: Sepulveda, Fernando E., Maschalidi, Sophia, Colisson, Renaud, Heslop, Lea, Ghirelli, Cristina, Sakka, Emna, Lennon-Duménil, Ana-Maria, Amigorena, Sebastian, Cabanie, Lucien, Manoury, Bénédicte
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 20.11.2009; Elsevier Limited
• Subjects: Animals; Cathepsins - metabolism; CELLIMMUNO; Cysteine Endopeptidases - genetics; Cysteine Endopeptidases - physiology; Dendritic Cells - immunology; Medical research; Mice; Mice, Knockout; Molecular weight; MOLIMMUNO; Mutagenesis; Proteins; Signal Transduction; Toll-Like Receptor 9 - metabolism; MOLIMMUNO; CELLIMMUNO
• ISSN: 1074-7613; 1097-4180
• DOI: 10.1016/j.immuni.2009.09.013

Intracellular Toll-like receptor 3 (TLR3), TLR7, and TLR9 localize in endosomes and recognize single-stranded RNA and nucleotides from viruses and bacteria. This interaction induces their conformational changes resulting in the production of proinflammatory cytokines and upregulation of cell surface molecules. TLR9 requires a proteolytic cleavage for its signaling. Here, we report that myeloid and plasmacytoid dendritic cells (DCs) deficient for the asparagine endopeptidase (AEP), a cysteine lysosomal protease, showed a decrease in the secretion of proinflammatory cytokines in response to TLR9 stimulation in vitro and in vivo. Upon stimulation, full-length TLR9 was cleaved into a 72 kDa fragment and this processing was strongly reduced in DCs lacking AEP. Processed TLR9 coeluted with the adaptor molecule MyD88 and AEP after size exclusion chromatography. When expressed in AEP-deficient DCs, the 72 kDa proteolytic fragment restored TLR9 signaling. Thus, our results identify an endocytic protease playing a critical role in TLR processing and signaling in DCs.