Molecular Hierarchies in Salivary Adaptive Responses

描述（由申请人提供）：唾液对维持口腔功能和健康至关重要。头颈部癌症和干燥综合征的放射治疗患者会对唾液腺造成不可逆的损伤，使其萎缩。该项目的长期目标是阐明唾液适应性反应所涉及的细胞和分子机制，特别是蛋白质修饰。泛素同源物、SUMO和磷酸化对蛋白质的修饰已被确定为调控转录、DNA修复、细胞周期进程和细胞内运输的重要调控机制。本申请将集中于SUMO化依赖性和蛋白激酶C5（PKC 8）介导的信号网络的串扰和各自的作用，分别在传递电阻和敏感性，对缺氧诱导的损伤唾液细胞。细胞缺氧是一种应激，在发育生物学、正常生理学和许多病理条件中具有重要意义，包括无数急性和慢性疾病状态和癌症。新出现的证据表明，缺氧调节许多不同类型的细胞的生物学和生化功能，然而，唾液细胞利用来抵消或加强缺氧诱导的细胞/DMA损伤和生长抑制的机制仍然不清楚。我们最近证明，缺氧导致SUMO化在唾液Pa-4细胞中的增加，这导致增强的NF-tcB介导的反式激活和PKC 8/caspase-3激活的衰减，表明SUMO依赖的蛋白质-蛋白质相互作用在调节唾液缺氧反应中起着至关重要的作用。此外，缺氧诱导的唾液适应性反应似乎还涉及磷脂酰肌醇激酶相关激酶（PIKK）家族成员，例如毛细血管扩张性共济失调突变（ATM），这表明缺氧导致累积的DMA损伤，导致细胞存活或生长抑制。因此，我们推测，唾液腺上皮细胞对缺氧的适应性反应介导的，至少部分，ATM激活，SUMO依赖的蛋白质-蛋白质相互作用及其相关的信号转导，和PKC 8激活之间的复杂平衡。为了验证我们的假设，我们提出了以下三个具体的目的：1）确定SUMO依赖的蛋白修饰在保护唾液腺上皮细胞免受缺氧诱导的损伤中的作用; 2）研究缺氧暴露后SUMO化依赖的和PKC 5介导的信号网络串扰，并阐明PKC 8激活在编程SUMO化促进的唾液腺上皮细胞缺氧耐受中的拮抗作用;和3）表征介导唾液腺上皮细胞对缺氧的适应性反应的SUMO化靶点。提出的机制研究将扩大我们目前的知识，在唾液腺缺氧引起的发病机制。从这项研究中获得的信息应导致创新的预防和治疗方法的发展，对病理表现的唾液腺，与干燥综合征和头部和颈部照射。

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.