DAB2IP-TACC3信号通路通过调控有丝分裂期纺锤体装配和有丝分裂灾变参与放射性肠损伤进程的作用机制研究

The small intestinal epithelium is highly sensitive to radiation and is a major site of injury during radiation exposure. However, molecular mechanisms underlying radiation-induced intestinal injuries have not been largely clarified. Mitotic catastrophe is considered as a major mode of cell death induced by irradiation. One potential cause of mitotic catastrophe is disordered organization of mitotic spindle, which is commonly induced by dysregulated dynamic of microtubules. Our preliminary data showed that DAB2IP-deficient mouse exhibited more severe IR-stimulated intestinal injury and decreasing of crypt proliferation and regeneration. Depletion of DAB2IP increased cells radiosensitivity and IR-induced mitotic catastrophe. DAB2IP localizes at the mitotic spindle structure and loss of DAB2IP inhibits microtubule nucleation. We also identified that DAB2IP interacts with TACC3 which acts as a plus end-tracking protein to promote microtubule polymerization. Based on the above evidence, we hypothesize that DAB2IP-TACC3 pathway might play essential role in coordinating DNA damage signal and mitotic spindle assembly. In this project, we will further determine: 1) the relationship between DAB2IP and TACC3; 2) the mechanism of DAB2IP-TACC3 signal pathway for the regulation of radiation induced mitotic catastrophe in intestine epithelial cells; 3) the contribution of DAB2IP-TACC3 in small intestine homeostasis maintenance and damaged tissues regeneration through an efficient control of cell mitotic progression.

小肠上皮是对电离辐射最敏感的部位之一，但辐射诱发肠道损伤的分子机制认识尚浅。有丝分裂灾变是辐射（IR）诱导细胞死亡的主要方式，其潜在诱因包括微管动态失调引起有丝分裂纺锤体的无序组织。我们前期工作显示DAB2IP缺陷小鼠表现出更严重的IR诱发的肠损伤并减缓隐窝增殖和再生。DAB2IP缺失增加细胞放射敏感性和IR诱导的有丝分裂灾变、抑制微管成核。DAB2IP定位于有丝分裂纺锤体结构，进一步发现其与TACC3相互作用。由于TACC3在微管正末端促进微管装配，我们推测DAB2IP-TACC3信号通路可能在协调DNA损伤信号和有丝分裂纺锤体装配中发挥重要作用。此项目进一步研究：1）DAB2IP和TACC3之间的关系; 2）DAB2IP-TACC3信号通路调节肠上皮细胞IR诱发的有丝分裂突变机制; 3）DAB2IP-TACC3通过有效调控细胞有丝分裂在维持小肠内平衡和受损组织再生中的作用。

肠隐窝中未分化细胞的增殖活性对于病理生理和应激条件下的肠道稳态更新和再生至关重要。DAB2IP作为肿瘤抑制因子，能够调节多种肿瘤相关通路。我们之前的研究表明，DAB2IP 是一种新的细胞周期调节因子，它通过促进有丝分裂进程中 PLK1 介导的功能。本课题，我们揭示了DAB2IP在电离辐射诱导的胃肠道损伤后肠道上皮稳态维持和肠道再生中的作用。 DAB2IP敲除导致小鼠隐窝中未分化细胞在不受干扰的条件下和暴露与射线后的增殖减少。此外，DAB2IP缺失小鼠的肠隐窝在离体类器官培养中表现出受损的存活和增殖能力。从机制上讲，DAB2IP与组蛋白乙酰转移酶HBO1相互作用并以Cdk1依赖性方式促进PLK1介导的HBO1磷酸化，DAB2IP通过这种方式促进H3 K14乙酰化、染色质上的MCM复合物加载和DNA复制进程。DAB2IP丢失会减慢DNA复制并增加复制压力，并随之而来的是基因组不稳定。先前的研究表明，ATR信号通路对于在不受干扰的条件下限制复制至关重要。我们描述了ATR抑制也有助于Cdk1介导的DAB2IP磷酸化。DAB2IP的磷酸化对于桥接HBO1和PLK1以及帮助PLK1介导的HBO1磷酸化和激活至关重要。突变的DAB2IP磷酸化通过基因组DNA的不完全复制加剧了基因组的不稳定性，表现为后期超细桥和53BP1核体在G1细胞周期阶段的积累。这项研究证明了DAB2IP在调节DNA 制方面的新作用，这对于维持基因组稳定性和快速增殖的组织稳态至关重要。