A systematic RNAi screen reveals involvement of endocytic pathway in neuronal dysfunction in alpha-synuclein transgenic C. elegans.
Mutations or multiplications in alpha-synuclein gene cause familial forms of Parkinson disease or dementia with Lewy bodies (LB), and the deposition of wild-type alpha-synuclein as LB 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 10 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.
Kuwahara
Tomoki
T
Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan.
Koyama
Akihiko
A
Koyama
Shingo
S
Yoshina
Sawako
S
Ren
Chang-Hong
CH
Kato
Takeo
T
Mitani
Shohei
S
Iwatsubo
Takeshi
T
D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics / Q000378:metabolism; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis; D006801:Humans; D009043:Motor Activity; D019636:Neurodegenerative Diseases / Q000378:metabolism / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D010766:Phosphorylation; D034622:RNA Interference; D013572:Synaptic Vesicles / Q000378:metabolism*; D051844:alpha-Synuclein / Q000235:genetics* / Q000378:metabolism / Q000633:toxicity
D029742:Caenorhabditis elegans Proteins; D018377:Neurotransmitter Agents; D051844:alpha-Synuclein