Nramp1 in macrophage defences against infections

描述(申请人提供)：传染病在北美重新成为一个主要的健康问题，部分原因是广泛出现的抗生素耐药性。对细胞内寄生虫的防御机制，以及细菌在宿主吞噬细胞中生存和复制的基本策略仍然知之甚少。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供新的策略。利用遗传方法，我们已经确定了吞噬细胞抗微生物防御的一个新成分(Nramp1)。小鼠的Nramp1基因突变导致对几种细胞内感染的易感性，人类NRAMP1基因的多态变异也与地方病地区分枝杆菌感染的易感性有关。Nramp1在巨噬细胞和中性粒细胞中形成的细菌吞噬体膜上表达，在那里它作为一个外排泵从吞噬小体空间中清除对微生物复制至关重要的二价金属。目前的建议描述了一系列旨在更好地了解Nramp1转运机制的实验，包括确定吞噬体膜上的首选底物。我们还希望确定分枝杆菌中依赖金属的生化途径和蛋白质，它们是巨噬细胞生存所必需的，并被Nramp1作用抑制。最后，我们最近定位了两个新的基因座(Trl-3，Trl-4)，它们以Nramp1非依赖的方式控制小鼠中结核分枝杆菌的肺复制。我们建议在同源小鼠品系中描述受Trl-3和Trl-4调控的宿主的生理反应、细胞种群和生化途径。还提出了潜在基因的定位克隆。这些联合研究可能会为传染病的干预提供新的途径和新的目标。

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.