Page A P, MacNiven K, Hengartner M O
Wellcome Unit of Molecular Parasitology, Anderson College, Glasgow University, Scotland, U.K.
Biochem J. 1996 Jul 1;317 ( Pt 1)(Pt 1):179-85. doi: 10.1042/bj3170179.
Cyclosporin A (CsA) is the most widely used immunosuppressive agent, whose properties are exerted via an interaction with cyclophilin, resulting in down-regulation of signal-transduction events in the T-cell. Cyclophilin is identical with peptidylprolyl cis-trans isomerase (PPI; EC 5.2.1.8), an enzyme which catalyses the isomerization between the two proline conformations in proteins, thereby acting as a catalyst in protein-folding events. Several reports indicate that CsA has potent anti-parasitic activity, effective against both protozoan and helminth species. In order to understand the various biological roles that cyclophilins play we have initiated a study of these proteins in the genetically tractable nematode Caenorhabditis elegans. Here we describe the cloning and characterization of 11 cyclophilin genes (cyp-1 to -11) derived from this nematode; this is currently the greatest number of isoforms described in a single species. Southern blotting and physical mapping indicated that these genes are dispersed throughout the nematode genome. A high degree of conservation exists between several isoforms, which also share characteristics with the ubiquitous isoforms previously described. The remaining isoforms are divergent, having altered CsA-binding domains and additional non-cyclophilin domains, which may impart compartmental specificity. Ten of these isoforms have been expressed in Escherichia coli, and the resultant fusion proteins have been examined biochemically for PPI activity, which they all possess. Isomerase activity is highest in the conserved and lowest in divergent isoforms, perhaps indicating a more specific substrate for the latter. Analysis of the C. elegans cyp genes will provide answers as to the roles played by cyclophilins in protein folding and signal transduction.
环孢素A（CsA）是应用最为广泛的免疫抑制剂，其作用是通过与亲环蛋白相互作用来实现的，从而导致T细胞中信号转导事件的下调。亲环蛋白与肽基脯氨酰顺反异构酶（PPI；EC 5.2.1.8）相同，该酶催化蛋白质中两种脯氨酸构象之间的异构化，从而在蛋白质折叠过程中起催化剂的作用。多项报告表明，CsA具有强大的抗寄生虫活性，对原生动物和蠕虫均有效。为了了解亲环蛋白发挥的各种生物学作用，我们启动了对基因易操作的线虫秀丽隐杆线虫中这些蛋白质的研究。在此，我们描述了从该线虫中克隆和鉴定的11个亲环蛋白基因（cyp-1至-11）；这是目前在单个物种中描述的异构体数量最多的情况。Southern印迹和物理图谱分析表明，这些基因分散在线虫基因组中。几种异构体之间存在高度保守性，它们也与先前描述的普遍存在的异构体具有共同特征。其余的异构体则有所不同，其亲环蛋白结合域发生了改变，并具有额外的非亲环蛋白结构域，这可能赋予了区室特异性。其中10种异构体已在大肠杆菌中表达，并且对所得的融合蛋白进行了PPI活性的生化检测，结果表明它们均具有该活性。异构酶活性在保守异构体中最高，在不同异构体中最低，这可能表明后者具有更特异的底物。对秀丽隐杆线虫cyp基因的分析将为亲环蛋白在蛋白质折叠和信号转导中所起的作用提供答案。
