Sepulveda Fernando E, Maschalidi Sophia, Colisson Renaud, Heslop Lea, Ghirelli Cristina, Sakka Emna, Lennon-Duménil Ana-Maria, Amigorena Sebastian, Cabanie Lucien, Manoury Bénédicte
Institut Curie, U932, 26 rue d'Ulm, 75005 Paris, France.
Immunity. 2009 Nov 20;31(5):737-48. doi: 10.1016/j.immuni.2009.09.013. Epub 2009 Oct 29.
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.
细胞内Toll样受体3（TLR3）、TLR7和TLR9定位于内体，识别来自病毒和细菌的单链RNA和核苷酸。这种相互作用诱导它们的构象变化，导致促炎细胞因子的产生和细胞表面分子的上调。TLR9的信号传导需要蛋白水解切割。在此，我们报告，缺乏天冬酰胺内肽酶（AEP，一种半胱氨酸溶酶体蛋白酶）的髓样和浆细胞样树突状细胞（DC）在体外和体内对TLR9刺激的反应中促炎细胞因子分泌减少。刺激后，全长TLR9被切割成一个72 kDa的片段，而在缺乏AEP的DC中这种加工过程显著减少。在尺寸排阻色谱后，加工后的TLR9与衔接分子髓样分化因子88（MyD88）和AEP共同洗脱。当在缺乏AEP的DC中表达时，72 kDa的蛋白水解片段恢复了TLR9信号传导。因此，我们的结果确定了一种内吞蛋白酶在DC的TLR加工和信号传导中起关键作用。
