Molecular Hierarchies in Salivary Adaptive Responses

描述(申请人提供)：唾液是维持口腔功能和健康的关键。接受放射治疗的头颈癌患者和干燥综合征患者的唾液腺会受到不可逆转的损害，导致唾液腺萎缩。该项目的长期目标是阐明唾液适应性反应中涉及的细胞和分子机制，特别是蛋白质修饰。泛素同系物、相扑和磷酸化的蛋白质修饰被认为是调控转录、DNA修复、细胞周期进展和细胞内运输的重要调节机制。这一应用将集中在SUMO化依赖和蛋白激酶C5(PKC8)介导的信号网络分别在传递对低氧诱导的唾液细胞损伤的抵抗和敏感性方面的串扰和个体作用。细胞缺氧是一种在发育生物学、正常生理学和许多病理条件下都具有重要意义的应激现象，包括各种急慢性疾病状态和癌症。新的证据表明，低氧调节许多不同类型细胞的生物学和生化功能，然而，唾液细胞利用来对抗或加强低氧诱导的细胞/DMA损伤和生长抑制的机制仍不清楚。我们最近的研究表明，低氧导致唾液PA-4细胞SUMO化水平的增加，导致NF-TCB介导的反式激活增强，PKC8/Caspase-3的激活减弱，这表明依赖于SUMO的蛋白质-蛋白质相互作用在调节唾液低氧反应中起着重要作用。此外，低氧诱导的唾液适应性反应似乎还涉及磷脂酰肌醇相关激酶(Pikk)家族成员，如共济失调毛细血管扩张突变(ATM)，这意味着低氧导致累积的DMA损伤，导致细胞存活或生长抑制。因此，我们假设唾液上皮对缺氧的适应性反应至少部分是由ATM激活、相扑依赖的蛋白质-蛋白质相互作用及其相关信号和PKC8激活之间的复杂平衡所介导的。为了验证我们的假设，我们提出了以下三个特定的目标：1)确定SUMO依赖的蛋白修饰在保护唾液上皮细胞免受低氧损伤中的作用；2)研究低氧暴露时的SUMO化依赖和PKC5介导的信号网络串扰，并描述PKC8激活在编程SUMO化促进唾液上皮细胞耐缺氧中的拮抗作用；以及3)表征介导唾液上皮细胞对低氧的适应性反应的SUMO化靶点。提出的机制研究将扩展我们目前对唾液腺低氧致病机制的认识。从这项研究中获得的信息应该有助于开发针对唾液腺与干燥综合征和头颈部照射相关的病理表现的创新预防和治疗方法。

DESCRIPTION (provided by applicant): Saliva is critical for the maintenance of oral function and health. Patients with radiation for head and neck cancer and with Sjogren's syndrome suffer irreversible damage to salivary glands, rendering them atrophic. The long-term goal of this project is to elucidate the cellular and molecular mechanisms, in particular protein modifications, involved in salivary adaptive responses. Protein modifications by the ubiquitin homologue, SUMO, and phosphorylation have been identified as important regulatory mechanisms governing transcription, DMA repair, cell cycle progression, and intracellular trafficking. This application will focus on the crosstalk and individual roles of SUMOylation-dependent and protein kinase C5 (PKC8)-mediated signaling network in conveying resistance and sensitivity, respectively, towards hypoxia-induced injury in salivary cells. Cellular hypoxia is a stress with important implications in the developmental biology, normal physiology, and many pathological conditions, including a myriad of acute and chronic disease states and cancers. Emerging evidence suggests that hypoxia regulates biological and biochemical functions in many different cell types, yet, the mechanisms by which salivary cells utilize to counteract or reinforce hypoxia-induced cell/DMA damage and growth inhibition are still not clear. We recently demonstrated that hypoxia leads to an increase in SUMOylation in salivary Pa-4 cells, which results in an enhanced NF-tcB-mediated transactivation and an attenuation of PKC8/caspase-3 activation, suggesting that SUMO-dependent protein-protein interaction plays an essential role in modulating salivary hypoxic responses. Further, hypoxia-induced salivary adaptive responses also appear to involve the phosphatidylinositol kinase-related kinase (PIKK) family members, such as ataxia telangiectasia mutate (ATM), implicating that hypoxia leads to cumulative DMA damage, rendering either cell survival or growth inhibition. Therefore, we hypothesize that salivary epithelial adaptive responses against hypoxia is mediated, at least in part, by an intricate balance among ATM activation, SUMO-dependent protein- protein interaction and its associated signaling, and PKC8 activation. To test our hypothesis, we propose the following three Specific Aims: 1) To establish the role of SUMO-dependent protein modification in protecting salivary epithelial cells against hypoxia-induced injury; 2) To investigate SUMOylation-dependent and PKC5-mediated signaling network crosstalk upon hypoxic exposure and delineate the antagonistic role by PKC8-activation in programming SUMOylation-promoted hypoxia tolerance in salivary epithelial cells; and 3) To characterize SUMOylation targets that mediate the adaptive responses to hypoxia in salivary epithelial cells. The proposed mechanistic studies will extend our current knowledge on hypoxia-elicited pathogenesis in salivary glands. Information obtained from this study should lead to the development of innovative prevention and therapeutic approach against pathological manifestations in salivary glands, associated with Sjogren's syndrome and head and neck irradiation.