Elements of the Ca2+ signal transduction pathway of Toxoplasma gondii

弓形虫是一种在宿主细胞内复制的专性细胞内寄生虫。刚地弓形虫属于 Apicomplexan门，也包括一些与医学和兽医相关的病原体。这个 这些疾病的临床表现是寄生虫在宿主细胞内生长的直接结果。复制 以及在宿主内传播是弓形虫致病的基本机制。弓形虫 参与多轮溶解循环，包括附着和分泌独特的粘附素， 宿主细胞的入侵、复制、出口和寻找另一宿主细胞的入侵。几乎所有这些生物 功能是由细胞内游离钙(Ca~(2+))的增加触发的，随后是信号的刺激 特征不佳的瀑布。钙离子下游的许多传导元件要么不是 已知或尚未确定其特征，或者它们与信令级联中其他元素的交互作用 安全。新的信号元件的发现和表征具有非常重要的意义，因为钙信号 构成弓形虫和其他相关病原体致病的信号机制的一部分。在……里面 此外，重要的寄生虫钙信号转导蛋白可作为抗寄生虫的靶点。 化疗。细胞内钙浓度的波动调节急性淋巴细胞白血病的各种细胞功能 真核生物。CA2信号始于细胞外钙离子内流引起的胞内钙离子浓度的增加 环境或从细胞内存储中释放。在瞬时钙信号中编码的信息通过以下方式解密 各种细胞内钙结合蛋白(CBP)，将信号转化为各种生化信号 改变。CBPS通过特定的结构域与钙结合，比如由EF-Hands组成的EF-Hand结构域。 钙调素(CaM)具有四个EF手，在钙信号转导中起核心作用，是钙信号传导的主要机制。 其中的钙信号被放大到蛋白质的规模，并被转化为生物反应。约束： CA2引发CaM形状的戏剧性变化，有利于其与靶蛋白的相互作用，导致不同的 诸如解除自身抑制、结构域结构的改变、活性部位的重塑以及蛋白质的作用 二聚化。在这个方案中，我们的目标是通过探索弓形虫CaM来发现新的钙信号转导蛋白 (TgCaM)结合传感器。对TgCaM及其下游传感器几乎一无所知，这很可能 通过从钙信号中传递信息，在弓形虫中发挥重要作用。很可能会有一些 目标/传感器已被识别，但其激活的机械基础，可能是通过绑定到 TgCaM尚未展示。我们相信，我们的工作将导致发现新的桥梁元素 钙信号通路提供了潜在的新的化疗靶点。此外，发现了 已建立的信号通路中的新蛋白质参与者有可能产生对 复杂信令网络的早期起源。

Toxoplasma gondii is an obligate intracellular parasite that replicates inside host cells. T. gondii belongs to the Apicomplexan phylum which also includes a number of pathogens of medical and veterinary relevance. The clinical manifestations of these diseases are a direct result of the growth of parasites within host cells. Replication and dissemination within the host are essential mechanisms by which T. gondii causes disease. T. gondii engages in multiple rounds of a lytic cycle, which consists of attachment and secretion of unique adhesins, invasion of host cells, replication, egress and search of another host cell to invade. Almost all of these biological functions are triggered by an increase in cytosolic free calcium (Ca2+), followed by stimulation of signaling cascades that are poorly characterized. Many of the transducing elements downstream to Ca2+ are either not known or have not been characterized or their interaction with other elements in the signaling cascade is not clear. Discovery and characterization of new signaling elements is highly significant because Ca2+ signaling forms part of the signaling mechanisms by which T. gondii and other related pathogens, cause disease. In addition, essential parasite calcium signaling players can be developed as targets for anti-parasitic chemotherapy.Fluctuations of the cytosolic Ca2+ concentration regulate a variety of cellular functions in all eukaryotes. Ca2+ signaling starts by an increase in cytosolic Ca2+ that results from influx from the extracellular milieu or release from intracellular stores. The information encoded in transient Ca2+ signals is deciphered by various intracellular Ca2+ binding proteins (CBPs) that convert the signals into a wide variety of biochemical changes. CBPs bind Ca2+ through specific domains like the EF-hand domains composed of EF-hands. Calmodulin (CaM), with four EF hands plays a central role in Ca2+ signaling and it is the main mechanism by which Ca2+ signals are amplified to the scale of proteins and is transduced into biological responses. Binding of Ca2+ triggers a dramatic change in CaM shape favoring its interaction with target proteins resulting in diverse effects like relieve of autoinhibition, changes in domains structures, remodeling of active sites and also protein dimerization. In this proposal we aim at discovering new Ca2+ signaling players by exploring T. gondii CaM (TgCaM) binding sensors. Almost nothing is known about TgCaM and its downstream sensors, which most likely play essential roles in T. gondii by transducing information from Ca2+ signals. It is likely that some of the targets/sensors have been identified but the mechanistic basis for their activation, potentially by binding to TgCaM has not been shown. We believe that our work will lead to the discovery of novel bridging elements in the Ca2+ signaling cascade offering potentially novel chemotherapeutic targets. Additionally, the discovery of new protein players within established signaling pathways has the potential to generate novel insight into the early origins of complex signaling networks.