title: Mutant protein kinase C gamma that causes spinocerebellar ataxia type 14 (SCA14) is selectively degraded by autophagy.
abstract: Several causal missense mutations in the protein kinase Cgamma (gammaPKC) gene have been found in spinocerebellar ataxia type 14 (SCA14), an autosomal dominant neurodegenerative disease. We previously showed that mutant gammaPKC found in SCA14 is susceptible to aggregation and causes apoptosis. Aggregation of misfolded proteins is generally involved in the pathogenesis of many neurodegenerative diseases. Growing evidence indicates that macroautophagy (autophagy) is important for the degradation of misfolded proteins and the prevention of neurodegenerative diseases. In the present study, we examined whether autophagy is involved in the degradation of the mutant gammaPKC that causes SCA14. Mutant gammaPKC-GFP was transiently expressed in SH-SY5Y cells by using an adenoviral tetracycline-regulated system. Subsequently, temporal changes in clearance of aggregates and degradation of gammaPKC-GFP were evaluated. Rapamycin, an autophagic inducer, accelerated clearance of aggregates and promoted degradation of mutant gammaPKC-GFP, but it did not affect degradation of wild-type gammaPKC-GFP. These effects of rapamycin were not observed in embryonic fibroblast cells from Atg5-deficient mice, which are not able to perform autophagy. Furthermore, lithium, another type of autophagic inducer, also promoted the clearance of mutant gammaPKC aggregates. These results indicate that autophagy contributes to the degradation of mutant gammaPKC, suggesting that autophagic inducers could provide therapeutic potential for SCA14.
authors.affiliation: Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Takahiro
authors.initials: T
authors.lastname: Seki
authors.forename: Naoko
authors.initials: N
authors.lastname: Adachi
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Takahashi
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tanaka
authors.forename: Izumi
authors.initials: I
authors.lastname: Hide
authors.forename: Naoaki
authors.initials: N
authors.lastname: Saito
authors.forename: Norio
authors.initials: N
authors.lastname: Sakai
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D018692:Antimanic Agents / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D018021:Lithium Chloride / Q000494:pharmacology; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D020754:Spinocerebellar Ataxias / Q000201:enzymology* / Q000235:genetics
chemical_list: D000903:Antibiotics, Antineoplastic; D018692:Antimanic Agents; D007527:Isoenzymes; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D016271:Proto-Oncogene Proteins c-myc; D011993:Recombinant Fusion Proteins; C087857:protein kinase C gamma; D011493:Protein Kinase C; D018021:Lithium Chloride; D020123:Sirolimus