LRP16通过呈递DNA损伤早期反应信号激活IKK的分子机制及可能的病理生理学意义研究

Genotoxin agents, such as ionizing radiation and genotoxic chemicals, can active NF-kB through the activation of IKK. However, the early molecular events for IKK activation after DNA damage is still poorly understood. LRP16 gene was initially cloned by our group. Recently, our findings demonstrated that LRP16 translocated swiftly from nucleus into cytoplasm upon DNA damage and transiently interacted with PKR, IKKb, NEMO in cytoplasm, and then returned back to the nucleus. Inhibition of LRP16 remarkably suppressed IKK activation and NF-kB activity induced by genotoxin agents; whereas,overexpression of LRP16 showed the reverse results. Our preliminary data suggested that LRP16 should paly a pivotal role for the early-phase activation of IKK functional complex in cells upon cellular exposure to genotoxin agents, and also suggested a novel molecular signaling for IKK activation conferred by LRP16. In this study, we will: 1) clarify the dynamics and the involved molecular mechanisms of the nuclear export of LRP16 induced by DNA damage using tumor cell lines and the primary cells; 2) dissect the essential components of LRP16-based functional complexes for IKK activation in cytoplasm, molecular bases of their interactions, and the mechanisms by which IKK complex, and subsequent NF-kB are activated. 3) establish the potential relationship between LRP16 expression or subcellular distribution, and/or IKK activity at the tissue pathological level, and establish their potential contribution to tumor chemoradiotherapy sensitivity in animal models with tumor graft and in patients. The accomplishment of this program will reveal a new molecule pathway mediating the IKK activation at the early phase of DNA damage.

电离辐射等DNA损伤剂通过激活IKK激活NF-kB，但对IKK激活的早期分子事件有待进一步阐明。LRP16是本研究组克隆的一个基因。近期，我们的研究结果显示DNA损伤后，LRP16快速的由细胞核穿梭到细胞浆，然后再回到核，并在胞浆内与PKR、IKKb、NEMO等分子相互作用；抑制LRP16显著抑制了DNA损伤剂诱导的IKK及NF-kB活性，过表达时则相反。提示LRP16在DNA损伤早期诱导IKK激活的过程中发挥关键作用，同时提示了一条新的IKK激活途径。本项目将：1）利用细胞系及原代细胞从分子水平阐明DNA损伤剂诱发LRP16出核的机制；2）细化解析LRP16出核后形成蛋白复合体的关键组份、相互作用的分子基础及激活IKK的机制；3）从实验动物及肿瘤组织层面研究LRP16表达/亚细胞分布与IKK活性及放化疗敏感性之间的相关性。本项目的完成将揭示一条DNA损伤早期激活IKK的新的分子途径。

电离辐射等DNA损伤剂通过激活IKK激活NF-κB，但对IKK激活的早期分子事件有待进一步阐明。本项目中，我们1）利用细胞系从分子水平阐明了DNA损伤剂诱发LRP16出核的机制；2）细化解析了LRP16在细胞核、细胞浆形成蛋白复合体的关键组份、相互作用的分子基础及激活IKK的机制；3）从实验动物及肿瘤组织层面研究了LRP16表达与IKK活性及放化疗敏感性之间的相关性。结果发现LRP16可以组成性的与PARP1、IKKγ等蛋白存在相互作用，并且在IKKγ的磷酸化与SUMO化中发挥重要作用，在此基础上，我们对其机制进行了深入研究，发现LRP16通过与Ku70、Ku80相互作用从而介导双链DNA断裂特异性的激活NF-κB，LRP16介导DNA损伤诱导的NF-κB激活依赖于其poly（ADP-ribose）（PAR））结合能力。在动物实验中我们发现，抑制LRP16的表达可以增加肿瘤对辐射的敏感性，通过对宫颈癌组织标本的检测和病例分析，我们发现LRP16的表达与肿瘤对辐射的敏感性呈负相关。该部分研究结果已发表于《Nucleic Acids Research》、《中国生物化学与分子生物学报》、《现代肿瘤医学》等杂志。在对浆内复合体的解析中，我们发现LRP16可与募集PKR、IKKβ等蛋白，促进NF-κB的激活，通过阻断LRP16与PAR的结合可以增加结直肠癌细胞对DNA损伤类化疗药的敏感性。本项目的完成揭示了LRP16在DNA损伤诱导NF-κB激活过程中的重要作用及分子机制，提示其在肿瘤治疗抵抗中的重要价值，为肿瘤放化疗增敏提供可供参考的新策略。

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