title: Glucocerebrosidase deficiency accelerates the accumulation of proteinase K-resistant α-synuclein and aggravates neurodegeneration in a Drosophila model of Parkinson's disease.
abstract: Alpha-synuclein (αSyn) plays a central role in the pathogenesis of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Recent multicenter genetic studies have revealed that mutations in the glucocerebrosidase 1 (GBA1) gene, which are responsible for Gaucher's disease, are strong risk factors for PD and DLB. However, the mechanistic link between the functional loss of glucocerebrosidase (GCase) and the toxicity of αSyn in vivo is not fully understood. In this study, we employed Drosophila models to examine the effect of GCase deficiency on the neurotoxicity of αSyn and its molecular mechanism. Behavioral and histological analyses showed that knockdown of the Drosophila homolog of GBA1 (dGBA1) exacerbates the locomotor dysfunction, loss of dopaminergic neurons and retinal degeneration of αSyn-expressing flies. This phenotypic aggravation was associated with the accumulation of proteinase K (PK)-resistant αSyn, rather than with changes in the total amount of αSyn, raising the possibility that glucosylceramide (GlcCer), a substrate of GCase, accelerates the misfolding of αSyn. Indeed, in vitro experiments revealed that GlcCer directly promotes the conversion of recombinant αSyn into the PK-resistant form, representing a toxic conformational change. Similar to dGBA1 knockdown, knockdown of the Drosophila homolog of β-galactosidase (β-Gal) also aggravated locomotor dysfunction of the αSyn flies, and its substrate GM1 ganglioside accelerated the formation of PK-resistant αSyn. Our findings suggest that the functional loss of GCase or β-Gal promotes the toxic conversion of αSyn via aberrant interactions between αSyn and their substrate glycolipids, leading to the aggravation of αSyn-mediated neurodegeneration.
authors.affiliation: Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan and.
authors.forename: Mari
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan and.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Fujikake
authors.affiliation: Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan and.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Takeuchi
authors.affiliation: Laboratory for Molecular Membrane Neuroscience, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Kohyama-Koganeya
authors.affiliation: Laboratory for Molecular Membrane Neuroscience, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nakajima
authors.affiliation: Laboratory for Molecular Membrane Neuroscience, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hirabayashi
authors.affiliation: Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan and.
authors.forename: Keiji
authors.initials: K
authors.lastname: Wada
authors.affiliation: Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan and nagai@ncnp.go.jp.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nagai
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D029721:Drosophila Proteins / Q000235:genetics; D004331:Drosophila melanogaster / Q000378:metabolism; D019286:Endopeptidase K / Q000378:metabolism; D055785:Gene Knockdown Techniques; D005962:Glucosylceramidase / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D005963:Glucosylceramides / Q000378:metabolism; D006801:Humans; D008297:Male; D020734:Parkinsonian Disorders / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D066263:Protein Aggregation, Pathological; D017510:Protein Folding; D051844:alpha-Synuclein / Q000378:metabolism*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D005963:Glucosylceramides; C497604:SNCA protein, human; D051844:alpha-Synuclein; D001616:beta-Galactosidase; D005962:Glucosylceramidase; D019286:Endopeptidase K