期刊
JOURNAL OF BIOCHEMISTRY
卷 140, 期 1, 页码 57-66出版社
OXFORD UNIV PRESS
DOI: 10.1093/jb/mvj132
关键词
aspartic proteinase; cathepsin E; knockout; macrophage; Toll-like receptors; trafficking
Cathepsin E, an intracellular aspartic proteinase, is predominantly localized in the endosomal compartments of immune system cells. In the present study, we investigated the role of cathepsin E in immune defense systems against bacterial infection. Cathepsin E-deficient (CatE(-/-)) mice showed dramatically increased susceptibility to infection with both the Gram-positive bacterium Staphyrococcus aureus, and the Gram-negative bacterium Porphyromonas gingivalis when compared with syngeneic wild-type mice, most likely due to impaired regulation of bacterial elimination. Peritoneal macrophages from CatE(-/-) mice showed significantly impaired tumor necrosis factor-a and IL-6 production in response to S. aureus and decreased bactericidal activities toward this bacterium. Moreover, the cell surface levels of Toll-like receptor-2 (TLR2) and TLR4, which recognize specific components of Gram-positive and -negative bacteria, respectively, were decreased in CatE(-/-) macrophages, despite no significant difference in the total cellular expression levels of these receptors between the wild-type and CatE(-/-) macrophages, implying trafficking defects in these surface receptors in the latter. These results indicate an essential role of cathepsin E in immune defense against invading microorganisms, most probably due to regulation of the cell surface expression of TLR family members required for innate immune responses.
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