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一个主要健康问题，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。更好地了解宿主对此类感染的防御可能会为干预这些疾病提出新的策略。使用遗传方法，我们已经确定了一个新的组成部分（Nramp 1）的抗菌防御吞噬细胞。小鼠NRAMP 1的突变导致对几种细胞内感染的易感性，人类NRAMP 1的多态性变体也与地方病地区对分枝杆菌感染的易感性相关。Nramp 1在巨噬细胞和嗜中性粒细胞中形成的细菌吞噬体的膜上表达，在那里它作为外排泵从吞噬体空间中去除微生物复制所必需的二价金属。目前的建议描述了一系列的实验，旨在更好地了解Nramp 1运输的机制，包括在吞噬体膜的首选底物的识别。我们还希望确定金属依赖的生化途径和蛋白质的分枝杆菌物种是必不可少的生存在巨噬细胞和Nramp 1行动的抑制。最后，我们最近绘制了2个新的基因座（Trl-3，Trl-4），以Nramp 1独立的方式控制小鼠肺结核分枝杆菌的复制。我们建议在同类系小鼠的生理反应，细胞群，和生化途径的主机，由Trl-3和Trl-4的特点。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.