School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive Northwest, Atlanta, GA 30332-0400, USA.
School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive Northwest, Atlanta, GA 30332-0400, USA.
J Mol Biol. 2014 Feb 20;426(4):921-35. doi: 10.1016/j.jmb.2013.12.002. Epub 2013 Dec 9.
The glaucoma-associated olfactomedin domain of myocilin (myoc-OLF) is a recent addition to the growing list of disease-associated amyloidogenic proteins. Inherited, disease-causing myocilin variants aggregate intracellularly instead of being secreted to the trabecular meshwork, which is a scenario toxic to trabecular meshwork cells and leads to early onset of ocular hypertension, the major risk factor for glaucoma. Here we systematically structurally and biophysically dissected myoc-OLF to better understand its amyloidogenesis. Under mildly destabilizing conditions, wild-type myoc-OLF adopts non-native structures that readily fibrillize when incubated at a temperature just below the transition for tertiary unfolding. With buffers at physiological pH, two main endpoint fibril morphologies are observed: (a) straight fibrils common to many amyloids and (b) unique micron-length, ~300 nm or larger diameter, species that lasso oligomers, which also exhibit classical spectroscopic amyloid signatures. Three disease-causing variants investigated herein exhibit non-native tertiary structures under physiological conditions, leading to a variety of growth rates and a fibril morphologies. In particular, the well-documented D380A variant, which lacks calcium, forms large circular fibrils. Two amyloid-forming peptide stretches have been identified, one for each of the main fibril morphologies observed. Our study places myoc-OLF within the larger landscape of the amylome and provides insight into the diversity of myoc-OLF aggregation that plays a role in glaucoma pathogenesis.
青光眼相关的肌球蛋白嗅素结构域(myoc-OLF)是越来越多的疾病相关淀粉样蛋白的一个新成员。遗传性致病肌球蛋白变体在细胞内聚集,而不是被分泌到小梁网,这种情况对小梁网细胞有毒,导致眼内高压的早期发生,眼内高压是青光眼的主要危险因素。在这里,我们系统地从结构和生物物理上对 myoc-OLF 进行了剖析,以更好地了解其淀粉样变性。在轻度去稳定条件下,野生型 myoc-OLF 采用非天然结构,在低于三级展开转变温度的温度下孵育时,很容易纤维化。在生理 pH 的缓冲液中,观察到两种主要的终点纤维形态:(a)许多淀粉样蛋白共有的直纤维,和(b)独特的微米长度、~300nm 或更大直径的物种,这些物种可以套住寡聚物,也表现出经典的光谱淀粉样特征。本文研究的三种致病变体在生理条件下表现出非天然的三级结构,导致各种生长速率和纤维形态。特别是,缺乏钙的有充分文献记载的 D380A 变体形成大的圆形纤维。已经确定了两个淀粉样肽伸展区,每个主要纤维形态都有一个。我们的研究将 myoc-OLF 置于更大的淀粉样蛋白组学景观中,并深入了解在青光眼发病机制中起作用的 myoc-OLF 聚集的多样性。