微管动力调节因子LIS1促进电离辐射损伤唾液腺细胞再生及功能恢复的作用及分子机制

放射性唾液腺炎是世界范围内临床难治性疾病，而腺泡细胞再生障碍和分泌功能降低是辐射损伤早期的重要病理特征。微管动力调节蛋白（LIS1）是新的干细胞调节因子和微管动力马达。我们前期研究发现电离辐射降低了LIS1在颌下腺的表达，且唾液腺干细胞标记分子Sca-1和SOX2亦随之下调，提示LIS1在辐射损伤唾液腺细胞内源性再生中具重要作用；同时，水通道蛋白5（AQP5）胞膜表达降低是唾液腺功能损伤的主要特征，AQP5的转位是以微管介导的脂质筏为载体，我们发现过表达LIS1促进了胞浆内AQP5向胞膜的转位，提示LIS1介导的微管运动可能促进了腺泡的分泌功能。故本课题拟研究LIS1介导的微管相关复合体在调控辐射后腺泡细胞纺锤体迁移、内源性干细胞再生和脂质筏运输AQP5中的作用及分子机制，阐释辐射损伤唾液腺细胞内源性再生和分泌功能修复的新靶点，为精准防治放射性唾液腺炎提供新策略。

Radiotherapy for head and neck cancer commonly leads to damage to normal tissues located in the radiation field, especially the salivary glands. As a result, patients inevitably developed radiation sialadenitis, mucositis, radiation caries, and xerostomia, all of which significantly affected their life quality. Thus, it is important to investigate the therapeutic approaches that can decrease the radiation damage to the salivary glands. .Depletion of endogenous stem cells and loss of acinar cells are the critical pathological characteristic in the early stage of radiation damage in salivary glands, leading to dysfunction of the salivary gland. Lissencephaly-1 (LIS1, also named Pafha1B1), a microtubule dynamic regulatory factor, has been identified as a novel regulator of stem cell in controlling cell mitosis and cytoskeleton regulation as well as membrane protein trafficking through interacting with microtubule-associated proteins. LIS1 is essential for precisely regulating mitotic spindle orientation in both neuroepithelial cells and radial glial progenitor cells and for mediating neural precursor/stem cell proliferation in the developing mammalian brain. LIS1 deficiency causes severe survival defects in a cell division-dependent manner owing to the dysregulation of centrosome formation and mitotic spindle assembly in the fetal liver. However, it remains unclear about the possible regulatory role of LIS1 in irradiated salivary glands..In our previous studies, we found that the expression of LIS1 was reduced by ionizing radiation (IR) in the rat submandibular gland and the salivary gland stem cell marker stem cell antigen 1 (Sca-1, the core molecule of cell regeneration) and SRY (sex-determining region Y)-box 2 (SOX2, the marker of adult salivary gland progenitor cells) were also decreased along with the downregulation of LIS1, suggesting that LIS1 plays an important role in the regeneration of salivary gland cells damaged by radiation. Meanwhile, the decreased expression of aquaporin 5 (AQP5) on the cellular membrane is the main feature of the dysfunction of the irradiated salivary gland. AQP5, an apical plasma membrane (APM) water channel in salivary glands, plays an important role in watery saliva secretion with translocation to APM from cytoplasm transporting by a particular subtype of lipid rafts, which is involved in various cellular events, such as signaling transduction, membrane sorting, and recycling and cell polarization. Interestingly, we found that overexpression of LIS1 in SMG-C6 cells with LIS1-overexpressing adenovirus can promote the translocation of intracellular AQP5 vesicles to the cellular membrane, indicating that LIS1 is associated with microtubule-raft interactions and might play an important role in regulating saliva secretion..Therefore, we speculate that the dysfunction of LIS1 is a new molecular mechanism of the regeneration and dysfunction of the salivary gland. Here we proposed to investigate the effects and mechanisms of LIS1 mediated microtubule-associated complex in regulating the spindle motion and regeneration of endogenous stem cell as well as the translocation of intracellular AQP5 in the submandibular gland after radiation. Our findings will help to elucidate the new protein target for promoting endogenous regeneration and restoring secretory function in the irradiated salivary gland, so as to provide a novel strategy for the precise prevention and treatment of radiation-induced salivary gland damages.