Visceral leishmaniasis is caused by the protozoan parasite Leishmania donovani. It is a fatal form of leishmaniasis prevalent in Indian subcontinent. Since there are no human licensed vaccines available for leishmaniasis, chemotherapeutic drugs remain the only means for combating parasitic infections. We have earlier identified a total of 26 amino-acyl tRNA synthetases (aaRS) along with five stand-alone editing domains and two aaRS-associated proteins in Leishmania donovani. In addition to their canonical role of tRNA aminoacylation, aaRS have been involved in novel functions by acquiring novel domains during evolution. The aaRS-associated proteins have been reported to be analogous to a human cytokine, EMAP II, as they possess a modified version of the heptapeptide motif responsible for the cytokine activity. In this manuscript, we report the characterization of two L. donovani aminoacyl-tRNA synthetase associated proteins which showed a human chemokine like activity. Both the proteins, L. donovani EMAP-1 and EMAP-2, possess a modified form of the heptapeptide motif, which is responsible for cytokine activity in human EMAP-2. LdEMAP-1 and LdEMAP-2 were cloned, expressed, and purified. Both LdEMAP-1 and LdEMAP-2 proteins in the promastigote stage were found to be localized in cytoplasm as confirmed by immunofluorescence. In case of L. donovani infected human THP-1 derived macrophages, secretion of LdEMAP-1 and LdEMAP-2 proteins in the cytosol of the macrophages was observed. The role of LdEMAP-1 and LdEMAP-2 in the aminoacylation of rLdTyrRS was also tested and LdEMAP-2 but not LdEMAP-1 increased the rate of aminoacylation of tyrosyl tRNA synthetase (rLdTyrRS). L. donovani EMAP-1 and EMAP-2 proteins managed to exhibit the capability of attracting human origin cells as determined by chemotaxis assay, and also were able to induce the secretion of cytokines from macrophages like their human counterpart (EMAP II). Our working hypothesis is that both of these proteins might be involved in helping the parasite to establish the infection within the host.

内脏利什曼病是由原生动物寄生虫杜氏利什曼原虫引起的。它是印度次大陆流行的一种致命的利什曼病。由于没有人类许可的利什曼病疫苗，化疗药物仍然是对抗寄生虫感染的唯一手段。前面我们已经有五个独立的编辑域和两个的aaRS相关蛋白一起共确定了26个氨基酰-tRNA合成酶（AARS）杜氏利什曼原虫. 除了 tRNA 氨酰化的典型作用外，aaRS 通过在进化过程中获得新的域而参与了新的功能。据报道，aaRS 相关蛋白类似于人类细胞因子 EMAP II，因为它们具有负责细胞因子活性的七肽基序的修饰版本。在这份手稿中，我们报告了两种杜氏乳杆菌氨酰-tRNA 合成酶相关蛋白的表征，这些蛋白显示出类似人类趋化因子的活性。这两种蛋白质，L. donovani EMAP-1 和 EMAP-2，都具有七肽基序的修饰形式，它负责人 EMAP-2 中的细胞因子活性。Ld EMAP-1 和Ld EMAP-2 被克隆、表达和纯化。两个都经免疫荧光证实，前鞭毛体阶段的Ld EMAP-1 和Ld EMAP-2 蛋白定位于细胞质中。在杜氏乳杆菌感染人 THP-1 衍生巨噬细胞的情况下，观察到巨噬细胞胞质溶胶中Ld EMAP-1 和Ld EMAP-2 蛋白的分泌。还测试了Ld EMAP-1 和Ld EMAP-2 在 r Ld TyrRS氨酰化中的作用，并且Ld EMAP-2 但不是Ld EMAP-1 增加了酪氨酰 tRNA 合成酶 (r Ld TyrRS)的氨酰化速率。多诺瓦尼EMAP-1 和 EMAP-2 蛋白设法表现出吸引人类起源细胞的能力，正如趋化性测定所确定的那样，并且还能够诱导巨噬细胞分泌细胞因子，如它们的人类对应物 (EMAP II)。我们的工作假设是这两种蛋白质都可能参与帮助寄生虫在宿主内建立感染。