Hegde Muralidhar L, Rao K S J
Department of Biochemistry and Nutrition, Central Food Technological Research Institute, Mysore 570020, India.
Arch Biochem Biophys. 2007 Aug 1;464(1):57-69. doi: 10.1016/j.abb.2007.03.042. Epub 2007 Apr 26.
Alpha-synuclein conformational modulation leading to fibrillation has been centrally implicated in Parkinson's disease. Previously, we have shown that alpha-synuclein has DNA binding property. In the present study, we have characterized the effect of DNA binding on the conformation and fibrillation kinetics of alpha-synuclein. It was observed that single-stranded circular DNA induce alpha-helix conformation in alpha-synuclein while plasmid supercoiled DNA has dual effect inducing a partially folded conformation and alpha-helix under different experimental conditions. Interestingly, alpha-synuclein showed a specificity for GC* nucleotide sequence in its binding ability to DNA. The aggregation kinetics data showed that DNA which induced partially folded conformation in alpha-synuclein promoted the fibrillation while DNA which induced alpha-helix delayed the fibrillation, indicating that the partially folded intermediate conformation is critical in the aggregation process. Further, the mechanism of DNA-induced folding/aggregation of alpha-synuclein was studied using effect of osmolytes on alpha-synuclein as a model system. Among the five osmolytes used, Glycerol, trimethylamine-N-oxide, Betaine, and Taurine induced partially folded conformation and in turn enhanced the aggregation of alpha-synuclein. The ability of DNA and osmolytes in inducing conformational transition in alpha-synuclein, indicates that two factors are critical in modulating alpha-synuclein folding: (i) electrostatic interaction as in the case of DNA, and (ii) hydrophobic interactions as in the case of osmolytes. The property of DNA inducing alpha-helical conformation in alpha-synuclein and inhibiting the fibrillation may be of significance in engineering DNA-chip based therapeutic approaches to PD and other amyloid disorders.
α-突触核蛋白的构象调节导致纤维化，这一过程在帕金森病中起着核心作用。此前，我们已经表明α-突触核蛋白具有DNA结合特性。在本研究中，我们表征了DNA结合对α-突触核蛋白构象和纤维化动力学的影响。据观察，单链环状DNA可诱导α-突触核蛋白形成α-螺旋构象，而质粒超螺旋DNA在不同实验条件下具有双重作用，可诱导部分折叠构象和α-螺旋。有趣的是，α-突触核蛋白在其与DNA的结合能力上对GC*核苷酸序列表现出特异性。聚集动力学数据表明，在α-突触核蛋白中诱导部分折叠构象的DNA促进了纤维化，而诱导α-螺旋的DNA则延迟了纤维化，这表明部分折叠的中间构象在聚集过程中至关重要。此外，以渗透剂对α-突触核蛋白的影响为模型系统，研究了DNA诱导α-突触核蛋白折叠/聚集的机制。在所使用的五种渗透剂中，甘油、三甲胺-N-氧化物、甜菜碱和牛磺酸诱导了部分折叠构象，进而增强了α-突触核蛋白的聚集。DNA和渗透剂诱导α-突触核蛋白构象转变的能力表明，两个因素在调节α-突触核蛋白折叠中至关重要：（i）如DNA情况下的静电相互作用，以及（ii）如渗透剂情况下的疏水相互作用。DNA在α-突触核蛋白中诱导α-螺旋构象并抑制纤维化的特性，可能在设计基于DNA芯片的帕金森病和其他淀粉样疾病治疗方法中具有重要意义。
