Amyloid-like Interactions in Yeast Cell Adhesion

描述(申请人提供)：细胞表面粘附素介导真菌与哺乳动物宿主的第一次相互作用，因此粘附素介导的结合是分化、定植、生物膜形成和病原体入侵的前奏。这些事件反过来会导致并发症的发病率和死亡率，特别是在免疫功能低下和慢性病患者中。白念珠菌粘附素参与了白念珠菌的发病机制和生物被膜的形成。它们与哺乳动物组织结合，引起真菌细胞聚集，也与其他微生物病原体共同聚集，介导多菌感染。肌萎缩侧索硬化症粘附素在组织和留置装置上形成持久性和抗药性生物膜方面也很重要。 我们的长期目标是了解细胞黏附蛋白在真菌生命周期和发病机制中的作用。这一建议的中心假设是，淀粉样蛋白形成序列是生物膜形成粘附素的特征，这些序列增强了黏附、真菌聚集和宿主入侵。这一假设是基于我们的发现，即Als5p导致粘连具有淀粉样蛋白的特征，纯化的Als5p可以形成真正的淀粉样蛋白，生物信息学分析揭示了许多与生物膜相关的微生物粘附素中的淀粉样蛋白形成序列。 有三个特定的目标将检验淀粉样蛋白/生物膜假说：(1)为了确定特定序列在淀粉样蛋白形成和微生物黏附中的作用，我们将检验淀粉样蛋白形成序列对于ALS介导的细胞聚集至关重要的工作假说。(2)我们将检验这样的假设，即ALS蛋白中的这些淀粉样蛋白形成序列是ALS启动的生物膜形成所必需的。(3)在ALS蛋白中，糖基化串联重复序列遵循淀粉样蛋白形成序列，这些重复序列极大地增加了黏附活性。因此，我们将测试这一假设，即ALS重复序列中的肽序列和糖基化模式调节淀粉样蛋白的形成，以促进细胞聚集和生物膜的形成。 拟议的工作是创新的，它结合了两个重要的概念：淀粉样蛋白相互作用和病原体的黏附导致生物膜的形成。我们也是第一个研究致病和其他真菌粘附素中富含苏氨酸重复序列的结构和功能的小组。完成这些目标将导致更好地定义生物膜形成的初始事件的模型，并将发现淀粉样蛋白形成序列是否对真菌中的生物膜附着是必不可少的。如果这一假设得到支持，结果将在寻找抗生物膜和抗淀粉样蛋白治疗剂之间建立联系。

DESCRIPTION (provided by applicant): Cell surface adhesins mediate the first interactions of fungi with mammalian hosts, so adhesin-mediated binding is a prelude to differentiation, colonization, biofilm formation and pathogenic invasion. These events in turn lead to complications of morbidity and mortality, especially common in immunocompromised and chronic disease patients. The C. albicans Als adhesins are implicated in pathogenesis and biofilm formation. They bind to mammalian tissues, cause fungal cell aggregation, and also co-aggregate with other microbial pathogens to mediate polymicrobial infections. Als adhesins are also important in formation of persistent and drug-resistant biofilms in tissues and on indwelling devices. Our long-term goal is to understand the roles for cell adhesion proteins in fungal life cycles and pathogenesis. The central hypothesis of this proposal is that amyloid-forming sequences are a feature of biofilm-forming adhesins, and these sequences potentiate adhesion, fungal aggregation and host invasion. This hypothesis is based on our findings that Als5p causes adherence with amyloid-like features, that the purified Als5p can form authentic amyloids, and that bioinformatic analyses reveal amyloid-forming sequences in many biofilm-associated microbial adhesins. Three specific aims will test the amyloid/ biofilm hypothesis: (1) To determine the role of specific sequences in amyloid formation and microbial adherence, we will test the working hypothesis that the amyloid-forming sequences are essential for Als-mediated cellular aggregation. (2) We will test the hypothesis that these amyloid-forming sequences in Als proteins are essential for Als-initiated biofilm formation. (3) In Als proteins, glycosylated tandem repeats follow the amyloid-forming sequences, and these repeats greatly increase adhesion activity. We will therefore test the hypothesis that the peptide sequences and glycosylation patterns in the Als repeats modulate amyloid formation to promote cellular aggregation and biofilm formation. The proposed work is innovative in its conjunction of two important concepts: amyloid-like protein interactions and adherence of pathogens leading to biofilm formation. We are also the first group to work on structure and function of Thr-rich repeat sequences in pathogenic and other fungal adhesins. Completion of these aims will lead to better defined models for the initial events in biofilm formation, and will discover whether amyloid-forming sequences are essential for biofilm adherence in fungi. If the hypothesis is supported, the results will establish connections between searches for anti-biofilm and anti-amyloid therapeutic agents.