Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8963289 | Neurobiology of Disease | 2018 | 17 Pages |
Abstract
Spinocerebellar ataxia type 21 (SCA21) is caused by missense or nonsense mutations of the transmembrane protein 240 (TMEM240). Molecular mechanisms of SCA21 pathogenesis remain unknown because the functions of TMEM240 have not been elucidated. We aimed to reveal the molecular pathogenesis of SCA21 using cell and mouse models that overexpressed the wild-type and SCA21 mutant TMEM240. In HeLa cells, overexpressed TMEM240 localized around large cytoplasmic vesicles. The SCA21 mutation did not affect this localization. Because these vesicles contained endosomal markers, we evaluated the effect of TMEM240 fused with a FLAG tag (TMEM-FL) on endocytosis and autophagic protein degradation. Wild-type TMEM-FL significantly impaired clathrin-mediated endocytosis, whereas the SCA21 mutants did not. The SCA21 mutant TMEM-FL significantly impaired autophagic lysosomal protein degradation, in contrast to wild-type. Next, we investigated how TMEM240 affects the neural morphology of primary cultured cerebellar Purkinje cells (PCs). The SCA21 mutant TMEM-FL significantly prevented the dendritic development of PCs, in contrast to the wild-type. Finally, we assessed mice that expressed wild-type or SCA21 mutant TMEM-FL in cerebellar neurons using adeno-associated viral vectors. Mice expressing the SCA21 mutant TMEM-FL showed impaired motor coordination. Although the SCA21 mutant TMEM-FL did not trigger neurodegeneration, activation of microglia and astrocytes was induced before motor miscoordination. In addition, immunoblot experiments revealed that autophagic lysosomal protein degradation, especially chaperone-mediated autophagy, was also impaired in the cerebella that expressed the SCA21 mutant TMEM-FL. These dysregulated functions in vitro, and induction of early gliosis and lysosomal impairment in vivo by the SCA21 mutant TMEM240 may contribute to the pathogenesis of SCA21.
Keywords
MEF2DLAMP2AMyocyte enhancer factor 2DMacroautophagyESCRTtetramethylrhodamineIBA1LC3PKCγAAVBGCprotein kinase CγCerebellar Purkinje cellsGCLHaloTagTSG101PCLDCNTransferrinCMALAMP1GFAPTMRHsc70MVBSPFADAMPslysosome-associated membrane protein 2aMicroautophagyChaperone-mediated autophagyMotor dysfunctiondamage-associated molecular patternsOregon Greenmultivesicular bodiesFlag tagDIVPurkinje cellBergmann glial cellgranule cell layerPurkinje cell layermolecular layerendosomal sorting complexes required for transportionized calcium-binding adapter molecule 1deep cerebellar nucleiAdeno-associated virusparaformaldehydeGlial fibrillary acidic proteinLysosomal-associated membrane protein 1Heat shock cognate protein 70microtubule associated protein 1 light chain 3mitogen-activated protein kinaseTumor susceptibility gene 101MAP kinaseGliosisGAPDH,
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Authors
Takahiro Seki, Masahiro Sato, Yuki Kibe, Tomoko Ohta, Mutsumi Oshima, Ayumu Konno, Hirokazu Hirai, Yuki Kurauchi, Akinori Hisatsune, Hiroshi Katsuki,