Enhanced lysosomal pathology caused by beta-synuclein mutants linked to dementia with Lewy bodies.
Two missense mutations (P123H and V70M) of beta-synuclein (beta-syn), the homologue of alpha-syn, have been recently identified in dementia with Lewy bodies. However, the mechanism through which these mutations influence the pathogenesis of dementia with Lewy bodies is unclear. To investigate the role of the beta-syn mutations in neurodegeneration, each mutant was stably transfected into B103 neuroblastoma cells. Cells overexpressing mutated beta-syn had eosinophilic cytoplasmic inclusion bodies immunopositive for mutant beta-syn, and electron microscopy revealed that these cells were abundant in various cytoplasmic membranous inclusions resembling the histopathology of lysosomal storage disease. Consistent with these findings, the inclusion bodies were immunopositive for lysosomal markers, including cathepsin B, LAMP-2, GM2 ganglioside, and ATP13A2, which has recently been linked to PARK9. Notably, formation of these lysosomal inclusions was greatly stimulated by co-expression of alpha-syn, was dependent on the phosphorylation of alpha-syn at Ser-129, and was more efficient with the A53T familial mutant of alpha-syn compared with wild type. Furthermore, the inclusion formation in cells overexpressing mutant beta-syn and transfected with alpha-syn was significantly suppressed by treatment with autophagy-lysosomal inhibitors, which were associated with impaired clearance of syn proteins and enhanced apoptosis, indicating that formation of lysosomal inclusions might be protective. Collectively, the results demonstrated unambiguously that overexpression of beta-syn mutants (P123H and V70M) in neuroblastoma cells results in an enhanced lysosomal pathology. We suggest that these missense mutations of beta-syn might play a causative role in stimulating neurodegeneration.
Wei
Jianshe
J
Laboratory for Chemistry and Metabolism, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.
Fujita
Masayo
M
Laboratory for Chemistry and Metabolism, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.
Nakai
Masaaki
M
Laboratory for Chemistry and Metabolism, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.
Waragai
Masaaki
M
Laboratory for Chemistry and Metabolism, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.
Watabe
Kazuhiko
K
Laboratory for Molecular Neuropathology, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan.
Akatsu
Hiroyasu
H
Choju Medical Institute, Fukushimura Hospital, Aichi 441-8124, Japan.
Rockenstein
Edward
E
Department of Neurosciences, University of California, San Diego, La Jolla, California 92093-0624.
Masliah
Eliezer
E
Department of Neurosciences, University of California, San Diego, La Jolla, California 92093-0624.
Hashimoto
Makoto
M
Laboratory for Chemistry and Metabolism, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526, Japan. Electronic address: mhashimoto@tmin.ac.jp.
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001343:Autophagy / Q000235:genetics; D015415:Biomarkers / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D006801:Humans; D016631:Lewy Bodies / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure*; D020961:Lewy Body Disease / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D020140:Lysosomal Storage Diseases, Nervous System / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D051846:beta-Synuclein / Q000235:genetics / Q000378:metabolism*
D015415:Biomarkers; D011506:Proteins; D051846:beta-Synuclein; C018589:lysosomal proteins