Iljina Marija, Tosatto Laura, Choi Minee L, Sang Jason C, Ye Yu, Hughes Craig D, Bryant Clare E, Gandhi Sonia, Klenerman David
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
Department of Molecular Neuroscience, University College London, Institute of Neurology, Queen Square, London WC1N 3BG, UK.
Sci Rep. 2016 Sep 27;6:33928. doi: 10.1038/srep33928.
The protein alpha-synuclein (αS) self-assembles into toxic beta-sheet aggregates in Parkinson's disease, while it is proposed that αS forms soluble alpha-helical multimers in healthy neurons. Here, we have made αS multimers in vitro using arachidonic acid (ARA), one of the most abundant fatty acids in the brain, and characterized them by a combination of bulk experiments and single-molecule Fӧrster resonance energy transfer (sm-FRET) measurements. The data suggest that ARA-induced oligomers are alpha-helical, resistant to fibril formation, more prone to disaggregation, enzymatic digestion and degradation by the 26S proteasome, and lead to lower neuronal damage and reduced activation of microglia compared to the oligomers formed in the absence of ARA. These multimers can be formed at physiologically-relevant concentrations, and pathological mutants of αS form less multimers than wild-type αS. Our work provides strong biophysical evidence for the formation of alpha-helical multimers of αS in the presence of a biologically relevant fatty acid, which may have a protective role with respect to the generation of beta-sheet toxic structures during αS fibrillation.
在帕金森病中，蛋白质α-突触核蛋白（αS）会自组装成有毒的β-折叠聚集体，而据推测，αS在健康神经元中会形成可溶性的α-螺旋多聚体。在此，我们利用花生四烯酸（ARA）在体外制备了αS多聚体，花生四烯酸是大脑中最丰富的脂肪酸之一，并通过大量实验和单分子Förster共振能量转移（sm-FRET）测量相结合的方法对其进行了表征。数据表明，ARA诱导的寡聚体是α-螺旋结构，抗纤维形成，更易于解聚、酶消化以及被26S蛋白酶体降解，并且与在无ARA情况下形成的寡聚体相比，导致的神经元损伤更低，小胶质细胞的激活减少。这些多聚体可以在生理相关浓度下形成，并且αS的病理突变体形成的多聚体比野生型αS少。我们的工作为在存在生物学相关脂肪酸的情况下αS形成α-螺旋多聚体提供了有力的生物物理证据，这可能对αS纤维化过程中β-折叠有毒结构的产生具有保护作用。
