Van Voorhis W C, Barrett L, Koelling R, Farr A G
Department of Medicine, School of Medicine, University of Washington, Seattle 98195.
J Exp Med. 1993 Aug 1;178(2):681-94. doi: 10.1084/jem.178.2.681.
The partial sequence of a gene encoding the COOH terminus of a protein of apparent molecular weight of 160 kD associated with the flagellum of trypomastigotes of Trypanosoma cruzi (FL-160 now renamed to FL-160-1) has been previously reported. The COOH terminus of FL-160-1 has an epitope, defined by 12 amino acids, which molecularly miMics a nervous tissue antigen of 48 kD found in myenteric plexus, sciatic nerve, and a subset of cells in the central nervous system. We now report that FL-160 is a family of highly related genes. The sequence has been determined for the entire open reading frame (ORF) of one of the members of the FL-160 gene family (FL-160-2) and three other partial ORFs. Sequence analysis reveals the various members of the FL-160 gene family to be approximately 80% homologous in the predicted amino acid sequence, but all retain the 12-amino acid molecular mimicry epitope on the COOH terminus. Comparison of the sequence of FL-160-2 to other sequences demonstrates amino acid homology to bacterial sialidase (27%), members of the SA85 gene family (25-30%) and the shed acute-phase antigen/neuraminidase/trans-sialidase gene family (25-30%). Quantitative hybridization at high stringency suggests 750 copies of FL-160 are present in the DNA of each parasite. Reverse transcription and sequence analysis demonstrates that at least five of the members of the FL-160 gene family are transcribed. The NH2 terminus of one of the FL-160 gene products was expressed and antibodies prepared. Antibodies directed to either the COOH or the NH2 terminus of FL-160 bind a 160-kD T. cruzi protein. Both antibodies bind the surface membrane in the flagellar pocket of the trypomastigote. Antibodies to the NH2 terminus bind epineurium and scattered linear densities in sciatic nerve in a pattern distinct from the pattern with antibodies to the COOH terminus. Thus, there are at least two distinct molecular mimicry epitopes on the FL-160 molecule and both mimic epitopes found in nervous tissues. FL-160 may be involved in the generation of autoimmunity to nervous tissues by molecular mimicry, observed in chronic Chagas' disease.
先前已报道了一个基因的部分序列，该基因编码与克氏锥虫无鞭毛体鞭毛相关的表观分子量为160 kD的蛋白质的COOH末端（FL - 160现重命名为FL - 160 - 1）。FL - 160 - 1的COOH末端有一个由12个氨基酸定义的表位，其在分子水平上模拟了在肠肌丛、坐骨神经和中枢神经系统的一部分细胞中发现的48 kD的神经组织抗原。我们现在报道FL - 160是一个高度相关的基因家族。已确定了FL - 160基因家族的一个成员（FL - 160 - 2）的整个开放阅读框（ORF）以及其他三个部分ORF的序列。序列分析表明，FL - 160基因家族的各个成员在预测的氨基酸序列中约80%同源，但在COOH末端均保留了12个氨基酸的分子模拟表位。将FL - 160 - 2的序列与其他序列进行比较，发现其与细菌唾液酸酶（27%）、SA85基因家族成员（25 - 30%）以及脱落的急性期抗原/神经氨酸酶/转唾液酸酶基因家族（25 - 30%）存在氨基酸同源性。高严谨度的定量杂交表明，每个寄生虫的DNA中存在750个FL - 160拷贝。逆转录和序列分析表明，FL - 160基因家族的至少五个成员被转录。表达了FL - 160基因产物之一的NH2末端并制备了抗体。针对FL - 160的COOH或NH2末端的抗体都能结合一种160 kD的克氏锥虫蛋白。两种抗体都能结合无鞭毛体鞭毛袋中的表面膜。针对NH2末端的抗体以一种与针对COOH末端的抗体不同的模式结合坐骨神经的神经外膜和散在的线性密度物质。因此，FL - 160分子上至少有两个不同的分子模拟表位，且这两个模拟表位都在神经组织中被发现。FL - 160可能通过分子模拟参与了在慢性恰加斯病中观察到的对神经组织的自身免疫的产生。
