Moore K J, Labrecque S, Matlashewski G
Institute of Parasitology, McGill University, Québec, Canada.
J Immunol. 1993 May 15;150(10):4457-65.
Leishmania donovani is an obligate intracellular protozoan which residues and multiples in macrophages. The molecular basis for this host-parasite interaction is poorly understood. Targeting a signal transduction pathway in the macrophage would allow this parasite to manipulate cellular gene expression, and this may aid in ensuring its survival. We demonstrate that in macrophages infected with L. donovani for 18 h, c-fos gene expression mediated through protein kinase A was unaffected under conditions where there was an impairment of protein kinase C (PKC)-mediated c-fos gene expression. This selective impairment of PKC-mediated c-fos gene expression was substantially augmented in macrophages put in contact with L. donovani promastigotes or amastigotes for only 1 h. Treatment of macrophages with L. donovani-conditioned media was not sufficient to significantly impair signal transduction. These data revealed that L. donovani selectively impaired the transmission of information from the cell surface to the nucleus and that this effect is induced very soon after macrophage-parasite contact. The biologic significance of this altered signal transduction in the macrophage with respect to infection with L. donovani was then examined by treating macrophages with various protein kinase inhibitors prior to infection with amastigotes. Macrophages that were treated with PKC inhibitors demonstrated an increase in the initial uptake of the parasite and carried heavier infection levels than did controls. In contrast, treatment of macrophages with an inhibitor of calmodulin-dependent protein kinase (CaM-PK) did not show significant differences in the initial uptake of parasite, but prolonged impairment of CaM-PK resulted in a decrease in the level of macrophage infection. Further experiments revealed that promastigote proliferation was severely impaired by the CaM-PK inhibitor but not any of the other inhibitors.
杜氏利什曼原虫是一种专性细胞内原生动物，寄生于巨噬细胞并在其中繁殖。这种宿主 - 寄生虫相互作用的分子基础尚不清楚。靶向巨噬细胞中的信号转导途径会使这种寄生虫能够操纵细胞基因表达，这可能有助于确保其存活。我们证明，在感染杜氏利什曼原虫18小时的巨噬细胞中，在蛋白激酶C（PKC）介导的c - fos基因表达受损的情况下，通过蛋白激酶A介导的c - fos基因表达未受影响。仅与杜氏利什曼原虫前鞭毛体或无鞭毛体接触1小时的巨噬细胞中，PKC介导的c - fos基因表达的这种选择性损伤会显著增强。用杜氏利什曼原虫条件培养基处理巨噬细胞不足以显著损害信号转导。这些数据表明，杜氏利什曼原虫选择性地损害了从细胞表面到细胞核的信息传递，并且这种效应在巨噬细胞与寄生虫接触后很快就会被诱导。然后，在巨噬细胞感染无鞭毛体之前用各种蛋白激酶抑制剂处理巨噬细胞，以研究巨噬细胞中这种改变的信号转导对杜氏利什曼原虫感染的生物学意义。用PKC抑制剂处理的巨噬细胞显示出寄生虫初始摄取量增加，并且感染水平比对照组更高。相比之下，用钙调蛋白依赖性蛋白激酶（CaM - PK）抑制剂处理巨噬细胞在寄生虫初始摄取方面没有显示出显著差异，但CaM - PK的长期损伤导致巨噬细胞感染水平下降。进一步的实验表明，CaM - PK抑制剂严重损害前鞭毛体增殖，但其他抑制剂均无此作用。
