Folding pathways for membrane-binding amphipathic helices

许多神经病理与蛋白质错误折叠成称为“β-淀粉样蛋白”的原纤维有关，包括帕金森氏病。一种错误折叠形式的蛋白质α-突触核蛋白积累在帕金森病患者大脑中的某些神经元中，并导致细胞死亡。 当α-突触核蛋白“正确”折叠时，它卷曲成螺旋并附着在储存神经递质的细胞内膜囊泡上。它在调节这些囊泡与细胞膜的融合和神经递质释放到突触中的生产功能是基于这种螺旋折叠。如果科学家能够找到一种方法来促进α-突触核蛋白的天然螺旋折叠，并阻止错误折叠成致病性原纤维，那么神经元细胞可能会从细胞死亡中拯救出来，帕金森病的症状可能会逆转。 我们在研究一种重要的代谢酶，胞苷酰转移酶（CCT）时发现，α-突触核蛋白在结构和功能上与CCT的尾部相似。 但是CCT是一种控制膜磷脂合成的酶，不会在细胞中错误折叠。 CCT，而不是α-突触核蛋白，含有一个球状头部结构域，可以防止其自身尾部的错误折叠。我们的建议有三个目的：（1）。平行表征突触核蛋白和CCT尾的结构和膜结合特性。 2）。确定CCT尾部在缺少与其头部结构域的连接时是否错误折叠成淀粉样颗粒或原纤维。 3）。评估CCT尾部结构域（如果未错误折叠）是否可作为伴侣蛋白防止α-突触核蛋白的错误折叠，或者评估由CCT头部结构域连接α-突触核蛋白组成的嵌合蛋白加入α-突触核蛋白时是否可防止错误折叠。 我们的研究将提供有关蛋白质错误折叠原因的基本信息。

Many neuropathologies are associated with protein mis-folding into fibrils called "beta-amyloid", including Parkinson's Disease. A mis-folded form of the protein alpha-synuclein accumulates in certain neurons in the brains of people with PD, and causes cell death. When alpha-synuclein folds "properly" it coils into a helix and attaches to intracellular membrane vesicles that store neurotransmitters. Its productive function in regulating the fusion of these vesicles with the cell membrane and neurotransmitter release into the synapse is predicated upon this helical folding. If scientists could find a way to promote the native helical folding of alpha-synuclein and discourage the mis-folding into pathogenic proto-fibrils, then the neuronal cells might be rescued from cell death, and Parkinson's Disease symptoms might be reversed. We have discovered during our studies of an important metabolic enzyme, cytidylyltransferase (CCT), that alpha-synuclein resembles the tail portion of CCT in structure and function. But CCT, which is an enzyme that controls the synthesis of membrane phospholipids, does not mis-fold in cells. CCT, but not alpha-synuclein, contains a globular head domain that could prevent mis-folding of its own tail. Our proposal has three aims: 1). To characterize in parallel the structure and membrane-binding properties of synuclein and the CCT tail. 2). To determine if the CCT tail mis-folds into amyloidogenic particles or fibrils when it is missing a connection to its head domain. 3). To assess whether the CCT tail domain (if it does NOT mis-fold) can serve as a chaperone to prevent mis-folding of alpha-synuclein, or alternatively to assess whether a chimeric protein composed of the CCT head domain linked to alpha-synuclein - when added to alpha-synuclein can prevent misfolding. Our research will provide basic information about the causes of protein mis-folding.