Activation mechanism of a NLR protein innate immune receptor

描述（由申请人提供）：监测微生物入侵的信号通常是启动免疫应答的第一步。然而，我们对影响免疫力的系统和机制缺乏充分的了解。我的长期目标是了解驱动细胞内识别微生物分子的“传感器”蛋白激活的过程。这些细胞内受体属于核苷酸结合结构域（NBD）富含亮氨酸重复序列（LRR）蛋白家族（一般称为NLR），并且是先天免疫系统的关键组分。这类基因的突变与人类疾病有关。考虑到NLR蛋白对人类健康和作物生产力的重要性，我们目前在分子水平上对NLR蛋白功能的理解是初步的。模式生物和人类生物学之间的知识转移加速了重大发现，因此了解NLR功能和激活将需要协调一致的跨学科方法。我将使用一个原型植物NLR，抗斑点假单胞菌1（RPM 1）作为NLR激活的功能模型。RPM 1通过效应子诱导的RPM 1- interacting 4（RIN 4）蛋白磷酸化间接识别两种不相关的致病性细菌III型效应子蛋白（AvrB和AvrRpm 1）。这种识别事件激活复杂的输出响应，导致感染部位的程序性细胞死亡和病原体定殖的限制。我们实验室最近发表和未发表的数据表明，磷酸化的RIN 4与RPM 1的亲和力大于未磷酸化的RIN 4。我假设效应诱导的RIN 4磷酸化增强了RPM 1和RIN 4的N-末端卷曲螺旋（CC）结构域之间的静电相互作用，从而产生稳定的相互作用，并导致RPM 1构象变化，从而缓解RPM 1 CC和LLR结构域施加的自抑制。这使得核苷酸交换/水解和随后的下游免疫信号传导成为可能。我的短期目标是测试我提出的模型，并使用本提案中强调的遗传和生物化学方法的混合来检查RPM 1激活的物理属性。拟议的研究将揭示一个鲜为人知的NLR激活过程。

DESCRIPTION (provided by applicant): Monitoring signals of microbial invasion is universally the first step in mounting an immune response. Yet we lack a full understanding of the systems and mechanisms that influence immunity. My long term goal seeks to understand the processes that drive the activation of intracellular "sensor" proteins that recognize microbial molecules. These intracellular receptors belong to the nucleotide-binding domain (NBD) leucine-rich repeat (LRR) protein family (generically termed NLRs), and are critical components of innate immune systems. Mutations in this class of genes have been implicated in human disease. Considering their importance across kingdoms for human health and crop productivity our current understanding of NLR protein function at the molecular level is rudimentary. Knowledge transfer between model organisms and human biology has accelerated prominent discoveries and thus understanding NLR function and activation will require a concerted interdisciplinary approach. I will use a prototypical plant NLR, Resistance to Pseudomonas maculicola 1 (RPM1) as a functional model for NLR activation. RPM1 indirectly recognizes two unrelated pathogenic bacterial type III effector proteins (AvrB and AvrRpm1) via effector-induced phosphorylation of the RPM1- interacting 4 (RIN4) protein. This recognition event activates a complex output response, resulting in programmed cell death at the infection site and restriction of pathogen colonization. Recent published and unpublished data from our laboratory suggests phosphorylated RIN4 associates with RPM1 with a greater affinity than does unphosphorylated RIN4. I hypothesize effector-induced phosphorylation of RIN4 enhances electrostatic interactions between the N-terminal coiled-coil (CC) domain of RPM1 and RIN4 entailing a stable interaction and leading to a RPM1 conformational change that relieves auto-inhibition imposed by the RPM1 CC and LLR domains. This enables nucleotide exchange/hydrolysis and subsequent downstream immune signaling. My short term goals are to test my proposed model and examine the physical attributes of RPM1 activation using a mixture of genetic and biochemical approaches highlighted in this proposal. The proposed research will shed light on a poorly understood NLR activation process.