Aggregation, Inhibition, Degradation: The Cystatin C-Beta-Amyloid-Cathepsin B System

退行性神经系统疾病，如阿尔茨海默氏症或帕金森氏症，是由蛋白质异常聚集成一种叫做“淀粉样蛋白”的沉积物引起的。淀粉样蛋白可以通过酶将蛋白质切割成无毒的片段，或者通过附着在蛋白质上的分子来防止结块。在这个项目中，将研究三种脑蛋白：(1)β -淀粉样蛋白（BA），形成与阿尔茨海默病相关的沉积物的蛋白质，(2)组织蛋白酶B，一种切割BA的酶，以及(3)胱抑素C，它可以形成淀粉样蛋白沉积物，阻止组织蛋白酶B降解BA，并附着在BA上并防止结块。这三种蛋白质之间的相互作用将被探索，为健康和患病脑细胞中的蛋白质聚集和降解提供新的知识，并可能为这些疾病的更有效的治疗策略提供一些线索。研究机会将提供给来自代表性不足群体的学生，并将修订本科工程文本，以纳入更多与蛋白质折叠疾病相关的例子。淀粉样原纤维是具有相同物理化学性质的蛋白质聚集体，如交叉-片结构和原纤维形态。由于淀粉样蛋白在神经退行性疾病中的重要性，许多研究都集中在单个淀粉样蛋白的聚集上。然而，蛋白质聚集不是孤立发生的，而是在相互竞争的复杂生物环境中发生的。胱抑素C、β -淀粉样蛋白和组织蛋白酶B构成了一个蛋白质聚集、结合和降解相互交织的网络。半胱抑素C是脑脊液的一种成分，在脑脊液中作为蛋白酶（如组织蛋白酶b）的抑制剂。半胱抑素C淀粉样沉积见于脑淀粉样血管病患者。β -淀粉样蛋白是一种生物学功能未知的肽，在阿尔茨海默病中聚集成淀粉样原纤维。组织蛋白酶B降解β -淀粉样蛋白，但被胱抑素C抑制。此外，胱抑素C与β -淀粉样蛋白结合可抑制β -淀粉样蛋白的纤维形成。因此，胱抑素C具有两种相反的作用：隔离β -淀粉样蛋白和防止纤维形成，同时抑制组织蛋白酶b介导的β -淀粉样蛋白水解。该项目的目标是：(1)表征半胱抑素C二聚体、低聚物和原纤维的结构和形成，(2)测量半胱抑素C对β -淀粉样蛋白聚集的影响，以及(3)确定半胱抑素C- β -淀粉样蛋白相互作用在组织蛋白酶B蛋白水解活性调节中的作用。实验数据将用于建立“淀粉样蛋白调控网络”的数学模型。识别这样一个网络，并探索其相互作用，将为健康和患病组织中蛋白质错误折叠、聚集和降解开辟新的研究方向。

Degenerative neurological disorders such as Alzheimer's or Parkinson's disease are caused by abnormal clumping of proteins into deposits called "amyloid". Amyloid can be prevented by enzymes that chop up the protein into nontoxic fragments, or by molecules that attach to the protein and prevent clumping. In this project, three brain proteins will be studied: (1) beta-amyloid (BA), the protein that forms deposits related to Alzheimer's disease, (2) cathepsin B, an enzyme that chops up BA, and (3) cystatin C, which can form amyloid deposits, prevents cathepsin B from degrading BA, and attaches to BA and prevents clumping. The interactions among these three proteins will be explored, providing new knowledge on protein clumping and degradation in healthy and diseased brain cells, and potentially providing some clues as to more effective treatment strategies for these diseases. Research opportunities will be provided to students from underrepresented groups, and an undergraduate engineering text will be revised to incorporate more examples related to protein folding diseases.Amyloid fibrils are protein aggregates that share physicochemical properties such as cross-beta-sheet structure and fibrillar morphology. Much research has focused on aggregation of individual amyloidogenic proteins because of their importance in neurodegenerative disorders. However, protein aggregation occurs not in isolation but in a complex biological milieu of competing interactions. The triad of cystatin C, beta-amyloid, and cathepsin B constitute a network in which protein aggregation, binding, and degradation are intertwined. Cystatin C is a constituent of cerebrospinal fluid, where it serves as an inhibitor of proteases such as cathepsin B. Cystatin C amyloid deposits are found in patients with cerebral amyloid angiopathy. Beta-amyloid is a peptide of unknown biological function that aggregates into amyloid fibrils in Alzheimer's disease. Cathepsin B degrades beta-amyloid but is inhibited by cystatin C. Furthermore, binding of cystatin C to beta-amyloid inhibits beta-amyloid fibrillogenesis. Thus, cystatin C has two opposing roles: sequestering beta-amyloid and preventing fibril formation, while inhibiting cathepsin B-mediated proteolysis of beta-amyloid. The objectives of this project are to (1) characterize the structure and formation of cystatin C dimers, oligomers, and fibrils, (2) measure the effect of cystatin C on beta-amyloid aggregation, and (3) determine the role of cystatin C- beta-amyloid interactions in regulation of cathepsin B proteolytic activity. The experimental data will be used to build a mathematical model of an "amyloid regulatory network". Identification of such a network, and exploration of its interactions, will open up new lines of inquiry in protein misfolding, aggregation, and degradation in healthy and diseased tissues.