Nramp1 in macrophage defences against infections

描述（由申请人提供）：传染病已重新成为北美的主要健康问题，部分原因是抗生素耐药性的广泛出现。对细胞内寄生虫的防御机制，以及宿主吞噬细胞中生存和复制的细菌策略仍然知之甚少。更好地了解宿主对这些感染的防御可能为干预这些疾病提供新的策略。利用遗传方法，我们已经确定了一个新的成分（Nramp1）的抗微生物防御吞噬细胞。小鼠Nramp1基因的突变导致对几种细胞内感染的易感性，人类Nramp1基因的多态性变异也与地方性疾病地区对分枝杆菌感染的易感性相关。Nramp1在巨噬细胞和中性粒细胞形成的细菌吞噬体膜上表达，在那里它作为外排泵从吞噬体空间中移除微生物复制所必需的二价金属。目前的提案描述了一系列旨在更好地理解Nramp1转运机制的实验，包括在吞噬体膜上识别首选底物。我们还希望确定分枝杆菌中金属依赖的生化途径和蛋白质，这些途径和蛋白质对巨噬细胞的生存至关重要，并被Nramp1的作用所抑制。最后，我们最近绘制了2个新的基因座（Trl-3、Trl-4），它们以不依赖于nramp1的方式控制小鼠结核分枝杆菌的肺复制。我们建议在同源小鼠系中表征由Trl-3和Trl-4调控的宿主生理反应、细胞群和生化途径。此外，还提出了潜在基因的定位克隆。这些综合研究可能为传染病的干预提供新的途径和新的靶点。

DESCRIPTION (provided by applicant): Infectious diseases have re-emerged as a major health problem in North America, in part due to the widespread emergence of antibiotics resistance. The mechanisms of defense against intracellular parasites, and the bacterial strategies underlying survival and replication in host phagocytes remain poorly understood. A better understanding of host defenses against such infections may suggest new strategies for intervention in these diseases. Using a genetic approach, we have identified a new component (Nramp1) of antimicrobial defenses of phagocytes. Mutations at Nramp1 in mice cause susceptibility to several intracellular infections, and polymorphic variants at human NRAMP1 are also associated with susceptibility to Mycobacterial infections in areas of endemic disease. Nramp1 is expressed at the membrane of bacterial phagosomes formed in macrophages and neutrophils, where it functions as an efflux pump to remove from the phagosomal space divalent metals essential for microbial replication. The current proposal describes a series of experiments aimed at better understanding the mechanism of Nramp1 transport, including the identification of the preferred substrate at the phagosomal membrane. We also wish to identify the metal dependent biochemical pathways and proteins in Mycobacterium species that are essential for survival in macrophages and that are inhibited by Nramp1 action. Finally, we have recently mapped 2 new loci (Trl-3, Trl-4) that control, in an Nramp1-independent fashion, the pulmonary replication of Mycobacterium tuberculosis in mice. We propose to characterize in congenic mouse lines the physiological responses, cell populations, and biochemical pathways of the host that are regulated by Trl-3 and Trl-4. The positional cloning of the underlying genes is also proposed. These combined studies may suggest new avenues and provide novel targets for intervention in infectious diseases.