Molecular Characterization of a Novel Family of Trypanosoma cruzi Surface Membrane Proteins (TcSMP) Involved in Mammalian Host Cell Invasion.
Molecular Characterization of a Novel Family of Trypanosoma cruzi Surface Membrane Proteins (TcSMP) Involved in Mammalian Host Cell Invasion.
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DOI：
10.1371/journal.pntd.0004216
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发表时间：
2015-11
影响因子：
3.8
通讯作者：
Silveira JF
中科院分区：
文献类型：
--
作者：
Martins NO;Souza RT;Cordero EM;Maldonado DC;Cortez C;Marini MM;Ferreira ER;Bayer-Santos E;Almeida IC;Yoshida N;Silveira JF
克氏锥虫的表面被膜主要由糖基磷脂酰肌醇锚定蛋白组成，其特征已被广泛表征。然而，很少有人知道丰富的表面蛋白质和它们在宿主-寄生虫相互作用的作用。在这里，我们描述了一个新的家庭T。cruzi表面膜蛋白（TcSMP）在不同T. cruzi谱系，并在其他锥虫属物种中具有直系同源物。TcSMP基因在基因组内密集聚集，表明它们可能起源于串联基因复制。几条线的证据表明，TcSMP是一种跨膜蛋白位于细胞表面，并被释放到细胞外环境。TcSMP具有典型的表面蛋白的关键元件（N-末端信号肽或信号锚）和预测为跨膜结构域的C-末端疏水序列。活虫免疫荧光显示抗TcSMP抗体清楚地标记了所有T. cruzi发育型。TcSMP肽先前发现在膜富集的部分中，通过蛋白质组学分析在膜囊泡中以及在T. cruzi分泌蛋白TcSMP蛋白也位于细胞内，可能与膜结合结构相关。我们证明了TcSMP蛋白能够抑制亚环锥鞭毛体进入宿主细胞。TcSMP与哺乳动物细胞结合并触发Ca 2+信号传导和溶酶体胞吐作用，这是寄生虫空泡生物发生所需的事件。TcSMP的影响是较低的幅度相比，gp 82，主要的粘附蛋白的亚循环锥鞭毛体，表明TcSMP可能发挥辅助作用，在宿主细胞的入侵。我们假设T.有效导致内化的宿主细胞的Cruzi可能依赖于不同的粘附分子。在元环形式中，由TcSMP诱导的信号传导可添加到由主要表面分子gp 82触发的信号传导，进一步增加感染所需的宿主细胞应答。 克氏锥虫是南美锥虫病的病原体，在全世界感染了600 - 700万人，主要是在拉丁美洲。目前，没有可用的疫苗，用于治疗的药物有毒，并不完全有效。为了感染哺乳动物宿主，T. Cruzi依赖于侵入宿主细胞、细胞内复制和在哺乳动物宿主的不同器官中传播感染的能力。对T. cruzi表面分子是理解寄生虫与其宿主相互作用的机制的基础。T. cruzi感染形式涉及一系列表面和分泌分子，其中一些参与触发寄生虫和宿主细胞中的信号传导途径，导致细胞内Ca 2+动员，这是寄生虫内化所必需的过程。在这里，我们描述了一个新的家庭T。cruzi表面膜蛋白（TcSMP），包括其基因组分布，表达和细胞定位。我们研究了TcSMP在宿主细胞侵袭中的作用机制，并提出了TcSMP在宿主细胞溶酶体胞吐过程中的触发作用。TcSMP基因在不同T. cruzi谱系，并在其他锥虫属物种中共享直系同源物。这些结果表明，TcSMP基因在哺乳动物锥虫的多样化发生在大陆漂移。于T. cruzi这个基因家族通过基因复制而扩大。
The surface coat of Trypanosoma cruzi is predominantly composed of glycosylphosphatidylinositol-anchored proteins, which have been extensively characterized. However, very little is known about less abundant surface proteins and their role in host-parasite interactions. Here, we described a novel family of T. cruzi surface membrane proteins (TcSMP), which are conserved among different T. cruzi lineages and have orthologs in other Trypanosoma species. TcSMP genes are densely clustered within the genome, suggesting that they could have originated by tandem gene duplication. Several lines of evidence indicate that TcSMP is a membrane-spanning protein located at the cellular surface and is released into the extracellular milieu. TcSMP exhibited the key elements typical of surface proteins (N-terminal signal peptide or signal anchor) and a C-terminal hydrophobic sequence predicted to be a trans-membrane domain. Immunofluorescence of live parasites showed that anti-TcSMP antibodies clearly labeled the surface of all T. cruzi developmental forms. TcSMP peptides previously found in a membrane-enriched fraction were identified by proteomic analysis in membrane vesicles as well as in soluble forms in the T. cruzi secretome. TcSMP proteins were also located intracellularly likely associated with membrane-bound structures. We demonstrated that TcSMP proteins were capable of inhibiting metacyclic trypomastigote entry into host cells. TcSMP bound to mammalian cells and triggered Ca2+ signaling and lysosome exocytosis, events that are required for parasitophorous vacuole biogenesis. The effects of TcSMP were of lower magnitude compared to gp82, the major adhesion protein of metacyclic trypomastigotes, suggesting that TcSMP may play an auxiliary role in host cell invasion. We hypothesized that the productive interaction of T. cruzi with host cells that effectively results in internalization may depend on diverse adhesion molecules. In the metacyclic forms, the signaling induced by TcSMP may be additive to that triggered by the major surface molecule gp82, further increasing the host cell responses required for infection. Trypanosoma cruzi is the etiologic agent of Chagas’ disease, which infects 6–7 million people worldwide, mostly in Latin America. Currently, there are no vaccines available, and the drugs used for treatment are toxic and are not fully effective. To infect mammalian hosts, T. cruzi relies on the ability to invade host cells, replicate intracellularly and spread the infection in different organs of the mammalian host. Knowledge of the structure and function of T. cruzi surface molecules is fundamental to understanding the mechanisms by which the parasite interacts with its host. T. cruzi infective forms engage a repertoire of surface and secreted molecules, some of which are involved in triggering signaling pathways both in the parasite and the host cell, leading to intracellular Ca2+ mobilization, a process essential for parasite internalization. Here, we described a novel family of T. cruzi surface membrane proteins (TcSMP), including their genomic distribution, expression and cellular localization. We studied the mechanism of action of TcSMP in host-cell invasion and proposed a triggering role for TcSMP in host-cell lysosome exocytosis during metacyclic internalization. TcSMP genes are conserved among different T. cruzi lineages and share orthologs in other Trypanosoma species. These results suggest that the diversification of TcSMP genes in mammalian trypanosomes occurred after continental drift. In T. cruzi this gene family expanded by gene duplication.