棘阿米巴是一种机会性致病原虫,在环境中普遍存在,一定条件下可以引起人体严重的甚至危及生命的感染。棘阿米巴生活史中具有致病性的滋养体期和有感染性的包囊期两个阶段。棘阿米巴成囊有两个阶段,分别是包括自溶和蛋白质降解的早期阶段和伴随着包囊特异性基因表达的晚期阶段。半胱氨酸蛋白酶在棘阿米巴成囊过程中的早期阶段起着重要作用,其成囊过程可以被半胱氨酸蛋白酶抑制剂E64d抑制。半胱氨酸蛋白酶是具有保守催化位点的组织蛋白L样酶,在滋养体和包囊中连续表达,分布在溶酶体内并在酸性条件下表现出最高的催化活性。与丝氨酸蛋白酶不同,半胱氨酸蛋白酶在成囊过程中水解多种蛋白质。包囊特异性半胱氨酸蛋白酶通过介导线粒体的自噬从而在棘阿米巴的成囊过程中起到关键作用,本文综述了内源性半胱氨酸蛋白酶抑制剂调节成囊过程的作用。
Acanthamoeba is an opportunistic protozoan widely distributed in the environment, and can cause severe and even life-threatening infections in humans. Acanthamoeba undergoes two stages during the life cycle: the pathogenic trophozoite stage and the infectious cyst stage. Further, there are two stages during encystment, including the early stage involving autolysis and protein degradation and the late stage with cyst-specific gene expression. Cysteine proteases play an important role in the early stage of encystment, which could be inhibited by the cysteine protease inhibitor E64d. Cysteine proteases are cathepsin L-like enzymes with a conserved catalytic site, expressed in trophozoites and cysts continuously, and are localized in lysosomes, exhibiting highest catalytic activities under acidic condition. Unlike serine proteases, cysteine proteases extensively hydrolyze proteins during the encystment process. The cystic-specific cysteine proteases play a key role in encystment of Acanthamoeba through mediating mitochondrial autophagy, this paper reviews the effects of endogenous cysteine protease inhibitors modulating the encystment process.
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