Phosphorylation of α-Synuclein Protein at Ser-129 Reduces Neuronal Dysfunction by Lowering Its Membrane Binding Property in Caenorhabditis elegans

alpha-Synuclein is causative for autosomal dominant familial Parkinson disease and dementia with Lewy bodies, and the phosphorylation of alpha-synuclein at residue Ser-129 is a key posttranslational modification detected in Parkinson disease/dementia with Lewy bodies lesions. However, the role of Ser-129 phosphorylation on the pathogenesis of Parkinson disease/dementia with Lewy bodies remains unclear. Here we investigated the neurotoxicity of Ser-129-substituted alpha-synuclein in the transgenic Caenorhabditis elegans (Tg worm) model of synucleinopathy. Tg worms pan-neuronally overexpressing nonphosphorylatable (S129A) alpha-synuclein showed severe defects including motor dysfunction, growth retardation, and synaptic abnormalities. In contrast, Tg worms expressing phosphorylation mimic (S129D) alpha-synuclein exhibited nearly normal phenotypes. Biochemical fractionation revealed that the level of membrane-bound alpha-synuclein was significantly increased in S129A-alpha-synuclein Tg worms, whereas S129D- as well as A30P-alpha-synuclein displayed lower membrane binding properties. Furthermore, A30P/S129A double mutant alpha-synuclein did not cause neuronal dysfunction and displayed low membrane binding property. In human neuroblastoma SH-SY5Y cells, localization of S129A-alpha-synuclein to membranes was significantly increased. Finally, gene expression profiling of S129A-Tg worms revealed a dramatic up-regulation of Daf-16/FOXO pathway genes, which likely act against the dysfunction caused by S129A-alpha-synuclein. These results imply a role of Ser-129 phosphorylation of alpha-synuclein in the attenuation of alpha-synuclein-induced neuronal dysfunction and downstream stress response by lowering the membrane binding property.