Reed S, Bouvier J, Pollack A S, Engel J C, Brown M, Hirata K, Que X, Eakin A, Hagblom P, Gillin F
Department of Pathology and Medicine, University of California, San Diego 92103-8416.
J Clin Invest. 1993 Apr;91(4):1532-40. doi: 10.1172/JCI116359.
Cysteine proteinases are hypothesized to be important virulence factors of Entamoeba histolytica, the causative agent of amebic dysentery and liver abscesses. The release of a histolytic cysteine proteinase from E. histolytica correlates with the pathogenicity of both axenic strains and recent clinical isolates as determined by clinical history of invasive disease, zymodeme analysis, and cytopathic effect. We now show that pathogenic isolates have a unique cysteine proteinase gene (ACP1). Two other cysteine proteinase genes (ACP2, ACP3) are 85% identical to each other and are present in both pathogenic and nonpathogenic isolates. ACP1 is only 35 and 45% identical in sequence to the two genes found in all isolates and is present on a distinct chromosome-size DNA fragment. Presence of the ACP1 gene correlates with increased proteinase expression and activity in pathogenic isolates as well as cytopathic effect on a fibroblast monolayer, an in vitro assay of virulence. Analysis of the predicted amino acid sequence of the ACP1 proteinase gene reveals homology with cysteine proteinases released by activated macrophages and invasive cancer cells, suggesting an evolutionarily conserved mechanism of tissue invasion. The observation that a histolytic cysteine proteinase gene is present only in pathogenic isolates of E. histolytica suggests that this aspect of virulence in amebiasis is genetically predetermined.
半胱氨酸蛋白酶被认为是溶组织内阿米巴的重要毒力因子，溶组织内阿米巴是阿米巴痢疾和肝脓肿的病原体。从溶组织内阿米巴释放的组织溶解性半胱氨酸蛋白酶与无菌培养菌株和近期临床分离株的致病性相关，这是通过侵袭性疾病的临床病史、酶谱分析和细胞病变效应确定的。我们现在表明，致病性分离株有一个独特的半胱氨酸蛋白酶基因（ACP1）。另外两个半胱氨酸蛋白酶基因（ACP2、ACP3）彼此有85%的同源性，且存在于致病性和非致病性分离株中。ACP1与在所有分离株中发现的两个基因在序列上只有35%和45%的同源性，并且位于一个不同大小染色体的DNA片段上。ACP1基因的存在与致病性分离株中蛋白酶表达和活性的增加以及对成纤维细胞单层的细胞病变效应相关，这是一种体外毒力测定。对ACP1蛋白酶基因预测氨基酸序列的分析揭示了与活化巨噬细胞和侵袭性癌细胞释放的半胱氨酸蛋白酶的同源性，表明存在一种进化上保守的组织侵袭机制。溶组织内阿米巴的组织溶解性半胱氨酸蛋白酶基因仅存在于致病性分离株中的这一观察结果表明，阿米巴病中毒力的这一方面是由基因预先决定的。
