Involvement of cathepsin E in exogenous antigen processing in primary cultured murine microglia
Involvement of cathepsin E in exogenous antigen processing in primary cultured murine microglia
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DOI：
10.1074/jbc.m108382200
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发表时间：
2002-02-15
影响因子：
4.8
通讯作者：
Nakanishi, H
中科院分区：
文献类型：
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作者：
Nishioku, T;Hashimoto, K;Nakanishi, H
我们试图阐明组织蛋白酶E（CE）参与主要组织相容性复合体II类介导的小胶质细胞抗原呈递。在原代培养的小鼠小胶质细胞中，CE主要定位于早期内体，并且其表达水平在干扰素-γ刺激后显著增加。胃蛋白酶抑制素A，一种特异性的天冬氨酸蛋白酶抑制剂，在用干扰素γ处理的小胶质细胞呈递的天然OVA刺激后，显著抑制了OVA-（266-281）特异性T辅助细胞杂交瘤的白细胞介素-2的产生。然而，胃酶抑素A不能抑制OVA-（266-281）肽的呈递。CE消化的天然OVA片段可被OVA特异性Th细胞识别，进一步证实了CE可能参与天然OVA加工成抗原肽。组织蛋白酶D也降解天然的卵蛋白成抗原肽，而从组织蛋白酶D缺陷小鼠制备的小胶质细胞保留了抗原呈递的能力。另一方面，在其特异性抑制剂的存在下，通过免疫印迹分析证实了在不变链（Ii）的加工中需要半胱氨酸蛋白酶如组织蛋白酶S和B。总之，CE是需要从卵清蛋白的抗原表位的产生，但不是Ii在小胶质细胞中的加工。
We have attempted to elucidate an involvement of cathepsin E (CE) in major histocompatibility complex class II-mediated antigen presentation by microglia. In primary cultured murine microglia, CE was localized mainly in early endosomes and its expression level was markedly increased upon stimulation with interferon-gamma. Pepstatin A, a specific inhibitor of aspartic proteases, significantly inhibited interleukin-2 production from an OVA-(266-281)-specific T helper cell hybridomas upon stimulation with native OVA presented by interferon-gamma-treated microglia. However, pepstatin A failed to inhibit the presentation of OVA-(266-281) peptide. The possible involvement of CE in the processing of native OVA into antigenic peptide was further substantiated by that digested fragments of native OVA by CE could be recognized by OVA-specific Th cells. Cathepsin D also degraded native OVA into antigenic peptide, whereas microglia prepared from cathepsin D-deficient mice retained an ability for antigen presentation. On the other hand, the requirement for cysteine proteases such as cathepsins S and B in the processing of invariant chain (Ii) was confirmed by immunoblot analyses in the presence of their specific inhibitors. In conclusion, CE is required for the generation of an antigenic epitope from OVA but not for the processing of Ii in microglia.