背景:朊病毒疾病是一种传染性和致命性的神经退行性疾病,其特征是错误折叠的朊病毒蛋白亚型(PrPSc)的积累,星形细胞增多症,小胶质细胞增生,海绵状体,和神经变性。细胞膜相关PrPSc蛋白和炎性细胞因子水平的升高提示着死亡受体(DR)途径的激活。DRs的激活调节,细胞存活或凋亡,自噬和坏死基于它们相互作用的衔接子。关于朊病毒疾病中DR途径的激活知之甚少。在正常小鼠大脑中表达的DR3和DR5从未在朊病毒疾病中研究过,它们的配体和任何DR衔接子也是如此。这一研究差距是值得注意的,并在本研究中进行了调查。
方法:C57BL/6J小鼠用落基山实验室瘙痒病小鼠朊病毒株感染。通过观察形态和行为异常来检查朊病毒病的进展。使用检测印迹和脑切片上的蛋白质的基于抗体的技术,分别测量PrP同种型和GFAP的水平作为PrPSc积累和星形细胞增生的标志物。DR的水平,它们的糖基化和胞外域脱落,和相关因素保证他们在蛋白质水平上的检查,因此,这项研究采用了蛋白质印迹分析。
结果:感染朊病毒的小鼠出现了运动障碍和神经病理学,如PrPSc积累和星形胶质细胞增多,类似于其他朊病毒疾病。这项研究的结果表明,所有DR配体的高表达,TNFR1、Fas和p75NTR但降低DR3和DR5水平。DR衔接蛋白如TRADD和TRAF2(主要调节促存活途径)的水平降低。FADD,主要调节细胞死亡,其水平保持不变。RIPK1调节促生存,凋亡和坏死,其表达和蛋白水解(抑制坏死但激活凋亡)增加。
结论:本研究的结果为DR3,DR5,DR6,TL1A的参与提供了证据。TRAIL,TRADD,TRAF2、FADD和RIPK1为首次在朊病毒疾病中的应用。从这项研究中获得的知识讨论了这16种差异表达的DR因子对我们对朊病毒疾病的多方面神经病理学的理解以及对朊病毒疾病特异性神经病理学的潜在靶向治疗干预的未来探索的可能影响。
BACKGROUND: Prion diseases are transmissible and fatal neurodegenerative diseases characterized by accumulation of misfolded prion protein isoform (PrPSc), astrocytosis, microgliosis, spongiosis, and neurodegeneration. Elevated levels of cell membrane associated PrPSc protein and inflammatory cytokines hint towards the activation of death receptor (DR) pathway/s in prion diseases. Activation of DRs regulate, either cell survival or apoptosis, autophagy and necroptosis based on the adaptors they interact. Very little is known about the DR pathways activation in prion disease. DR3 and DR5 that are expressed in normal mouse brain were never studied in prion disease, so also their ligands and any DR adaptors. This research gap is notable and investigated in the present study.
METHODS: C57BL/6J mice were infected with Rocky Mountain Laboratory scrapie mouse prion strain. The progression of prion disease was examined by observing morphological and behavioural abnormalities. The levels of PrP isoforms and GFAP were measured as the marker of PrPSc accumulation and astrocytosis respectively using antibody-based techniques that detect proteins on blot and brain section. The levels of DRs, their glycosylation and ectodomain shedding, and associated factors warrant their examination at protein level, hence western blot analysis was employed in this study.
RESULTS: Prion-infected mice developed motor deficits and neuropathology like PrPSc accumulation and astrocytosis similar to other prion diseases. Results from this research show higher expression of all DR ligands, TNFR1, Fas and p75NTR but decreased levels DR3 and DR5. The levels of DR adaptor proteins like TRADD and TRAF2 (primarily regulate pro-survival pathways) are reduced. FADD, which primarily regulate cell death, its level remains unchanged. RIPK1, which regulate pro-survival, apoptosis and necroptosis, its expression and proteolysis (inhibits necroptosis but activates apoptosis) are increased.
CONCLUSIONS: The findings from the present study provide evidence towards the involvement of DR3, DR5, DR6,
TL1A, TRAIL, TRADD, TRAF2, FADD and RIPK1 for the first time in prion diseases. The knowledge obtained from this research discuss the possible impacts of these 16 differentially expressed DR factors on our understanding towards the multifaceted neuropathology of prion diseases and towards future explorations into potential targeted therapeutic interventions for prion disease specific neuropathology.