A Systematic RNAi Screen Reveals Involvement of Endocytic Pathway in Neuronal Dysfunction in {alpha}-Synuclein Transgenic C. elegans

A Systematic RNAi Screen Reveals Involvement of Endocytic Pathway in Neuronal Dysfunction in {alpha}-Synuclein Transgenic C. elegans.

Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan.

Mutations or multiplications in alpha-synuclein gene cause familial forms of Parkinson disease or dementia with Lewy bodies, and the deposition of wild-type alpha-synuclein as Lewy bodies occurs as a hallmark lesion of these disorders, collectively referred to as synucleinopathies, implicating alpha-synuclein in the pathogenesis of synucleinopathy. To identify modifier genes of alpha-synuclein-induced neurotoxicity, we conducted an RNAi screen in transgenic C. elegans (Tg worms) that overexpress human alpha-synuclein in a pan-neuronal manner. To enhance the RNAi effect in neurons, we crossed alpha-synuclein Tg worms with an RNAi-enhanced mutant eri-1 strain. We tested RNAi of 1673 genes related to nervous system or synaptic functions, and identified ten genes that, upon knockdown, caused severe growth/motor abnormalities selectively in alpha-synuclein Tg worms. Among these were four genes (i.e., apa-2, aps-2, eps-8 and rab-7) related to the endocytic pathway, including two subunits of AP-2 complex. Consistent with the results by RNAi, crossing alpha-synuclein Tg worms with an aps-2 mutant resulted in severe growth arrest and motor dysfunction.?alpha-Synuclein Tg worms displayed a decreased touch sensitivity upon RNAi of genes involved in synaptic vesicle endocytosis, and they also showed impaired neuromuscular transmission, suggesting that overexpression of alpha-synuclein caused a failure in uptake or recycling of synaptic vesicles. Furthermore, knockdown of apa-2, an AP-2 subunit, caused an accumulation of phosphorylated alpha-synuclein in neuronal cell bodies, mimicking synucleinopathy. Collectively, these findings raise a novel pathogenic link between endocytic pathway and alpha-synuclein-induced neurotoxicity in synucleinopathy.

PMID: 18617532 [PubMed - as supplied by publisher]