Receptor Kinase-Mediated Signaling in the Innate Immune Response

描述（由申请人提供）：细胞表面受体感知细胞外信号对真核生物发育和免疫至关重要。这些受体中的许多在其胞质结构域（RKs）中具有内在蛋白激酶活性，并通过磷酸化事件调节靶基因的转录。异常调节可导致多种疾病，因此了解RK特异性和功能是如何控制的非常重要。 水稻Xa 21 RK是植物和动物之间广泛保守的病原体防御途径先天免疫反应中的关键识别和信号传导决定簇。XA 21作为病原体识别受体（PRR），在胞外结构域和非RD激酶结构域中具有富含亮氨酸的重复序列（LRR）。Xa 21活性在识别病原体相关分子模式（PAMP）AvrXa 21时触发，AvrXa 21是由革兰氏阴性细菌黄单胞菌黄单胞菌致病性金黄色葡萄球菌产生的硫酸化肽。- 是的 我们已经证明了XA 21 JM结构域在XA 21激酶介导的信号转导中起关键作用。特别地，XA 21 JM氨基酸残基丝氨酸697对于正调节功能和负调节功能都是关键的。当S697去磷酸化时，XA 21介导的抗性增强。磷酸化后，S697作为下游负调节因子XB 10和XB 15的高亲和力结合位点。我们和其他人还表明，在用携带AvrXa 21的Xoo菌株处理后，Xa 21在JM结构域被切割。我们假设，在AvrXa 21触发切割后，XA 21激酶结构域易位到细胞核，在那里它通过与Xb 10和其他蛋白质的相互作用影响下游信号传导。为了进一步验证这一假设，我们建议：1。探索XA 21激酶结构域向细胞核的AvrXa 21依赖性易位。2.进一步表征XA 21 S697 JM残基在XA 21介导的抗性中的作用。3.识别AvrXa 21激活后形成的核复合物RKs是一类重要的分子，介导植物和动物的基本过程。通过JM结构域调节RK信号传导到目前为止仅对控制重要细胞过程的少数受体家族是独特的，因此对探索这种控制的分子基础有很大的兴趣。拟议的研究将增强我们对JM结构域切割和释放的胞质结构域核转位的作用的理解。由于XA 21 PRR是植物和动物中非RD介导的先天免疫和受体激酶介导的信号传导的模型，因此本文提出的实验将广泛适用于公共卫生。

DESCRIPTION (provided by applicant): Perception of extracellular signals by cell surface receptors is of central importance to eukaryotic development and immunity. Many of these receptors possess intrinsic protein kinase activity in their cytoplasmic domains (RKs) and regulate transcription of target genes through phosphorylation events. Abnormal regulation can lead to a variety of diseases and it is therefore important to understand how RK specificity and function are controlled. The rice Xa21 RK is a key recognition and signaling determinant in the innate immune response, a pathogen defense pathway widely conserved between plants and animals. XA21 serves as a pathogen recognition receptor (PRR) with leucine rich repeats (LRRs) in the extracellular domain and a non-RD kinase domain. Xa21 activity is triggered upon recognition of the pathogen-associated molecular pattern (PAMP) AvrXa21, a sulfated peptide that is produced by the Gram-negative bacterium Xanthomonas oryzae pv. oryzae. We have shown the XA21 JM domain plays a key role in XA21 kinase-mediated signal transduction. In particular, the XA21 JM amino acid residue serine 697 is critical for both positive and negative regulatory functions. When S697 is dephosphorylated, XA21-mediated resistance is enhanced. Upon phosphorylation, S697 serves as a high affinity-binding site for the downstream negative regulators, XB10 and XB15. We and others have also shown that XA21 is cleaved at the JM domain after treatment with Xoo strains carrying AvrXa21. We hypothesize that, upon AvrXa21-triggered cleavage, the XA21 kinase domain is translocated to the nucleus where it affects downstream signaling through interaction with Xb10 and other proteins. To further test this hypothesis we propose to: 1. Explore AvrXa21-dependent translocation of the XA21 kinase domain to the nucleus. 2. Further characterize the role of XA21S697 JM residue in XA21-mediated resistance. 3. Identify nuclear complexes that form after AvrXa21 activation RKs are an important class of molecules that mediate fundamental processes in both plants and animals. Regulation of RK signaling through the JM domain is so far unique to only a few receptor families controlling important cellular processes and consequently there is great interest in exploring the molecular basis for this control. The proposed studies will enhance our understanding of the role of JM domain cleavage and nuclear translocation of the liberated cytoplasmic domain. Because the XA21 PRR is a model for non-RD mediated innate immunity and receptor-kinase mediated signaling in plants and animals, the experiments proposed here will be broadly applicable to public health.