Critical role for asparagine endopeptidase in endocytic Toll-like receptor signaling in dendritic cells.
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.
Sepulveda
Fernando E
FE
Institut Curie, U932, 26 rue d'Ulm, 75005 Paris, France.
Maschalidi
Sophia
S
Colisson
Renaud
R
Heslop
Lea
L
Ghirelli
Cristina
C
Sakka
Emna
E
Lennon-Duménil
Ana-Maria
AM
Amigorena
Sebastian
S
Cabanie
Lucien
L
Manoury
Bénédicte
B
D000818:Animals; D002403:Cathepsins / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000502:physiology*; D003713:Dendritic Cells / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D015398:Signal Transduction; D051217:Toll-Like Receptor 9 / Q000378:metabolism*; D000099240:Asparaginyl Endopeptidase
D002403:Cathepsins; D003546:Cysteine Endopeptidases; D051217:Toll-Like Receptor 9; D000099240:Asparaginyl Endopeptidase