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Liu Y, Tan L, Tan MS. Chaperone-mediated autophagy in neurodegenerative diseases: mechanisms and therapy. Mol Cell Biochem 2023; 478:2173-2190. [PMID: 36695937 DOI: 10.1007/s11010-022-04640-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 12/09/2022] [Indexed: 01/26/2023]
Abstract
Chaperone-mediated autophagy (CMA) is the selective degradation process of intracellular components by lysosomes, which is required for the degradation of aggregate-prone proteins and contributes to proteostasis maintenance. Proteostasis is essential for normal cell function and survival, and it is determined by the balance of protein synthesis and degradation. Because postmitotic neurons are highly susceptible to proteostasis disruption, CMA is vital for the nervous system. Since Parkinson's disease (PD) was first linked to CMA dysfunction, an increasing number of studies have shown that CMA loss, as seen during aging, occurs in the pathogenetic process of neurodegenerative diseases. Here, we review the molecular mechanisms of CMA, as well as the physiological function and regulation of this autophagy pathway. Following, we highlight its potential role in neurodegenerative diseases, and the latest advances and challenges in targeting CMA in therapy of neurodegenerative diseases.
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Affiliation(s)
- Yi Liu
- Department of Neurology, Qingdao Municipal Hospital, Qingdao University, Qingdao, China
| | - Lan Tan
- Department of Neurology, Qingdao Municipal Hospital, Qingdao University, Qingdao, China.
| | - Meng-Shan Tan
- Department of Neurology, Qingdao Municipal Hospital, Qingdao University, Qingdao, China.
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2
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Sato M, Ohta T, Morikawa Y, Konno A, Hirai H, Kurauchi Y, Hisatsune A, Katsuki H, Seki T. Ataxic phenotype and neurodegeneration are triggered by the impairment of chaperone-mediated autophagy in cerebellar neurons. Neuropathol Appl Neurobiol 2021; 47:198-209. [PMID: 32722888 DOI: 10.1111/nan.12649] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 07/13/2020] [Accepted: 07/15/2020] [Indexed: 12/13/2022]
Abstract
AIMS Chaperone-mediated autophagy (CMA) is a pathway involved in the autophagy lysosome protein degradation system. CMA has attracted attention as a contributing factor to neurodegenerative diseases since it participates in the degradation of disease-causing proteins. We previously showed that CMA is generally impaired in cells expressing the proteins causing spinocerebellar ataxias (SCAs). Therefore, we investigated the effect of CMA impairment on motor function and the neural survival of cerebellar neurons using the micro RNA (miRNA)-mediated knockdown of lysosome-associated protein 2A (LAMP2A), a CMA-related protein. METHODS We injected adeno-associated virus serotype 9 vectors, which express green fluorescent protein (GFP) and miRNA (negative control miRNA or LAMP2A miRNA) under neuron-specific synapsin I promoter, into cerebellar parenchyma of 4-week-old ICR mice. Motor function of mice was evaluated by beam walking and footprint tests. Immunofluorescence experiments of cerebellar slices were conducted to evaluate histological changes in cerebella. RESULTS GFP and miRNA were expressed in interneurons (satellite cells and basket cells) in molecular layers and granule cells in the cerebellar cortices, but not in cerebellar Purkinje cells. LAMP2A knockdown in cerebellar neurons triggered progressive motor impairment, prominent loss of cerebellar Purkinje cells, interneurons, granule cells at the late stage, and astrogliosis and microgliosis from the early stage. CONCLUSIONS CMA impairment in cerebellar interneurons and granule cells triggers the progressive ataxic phenotype, gliosis and the subsequent degeneration of cerebellar neurons, including Purkinje cells. Our present findings strongly suggest that CMA impairment is related to the pathogenesis of various SCAs.
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Affiliation(s)
- Masahiro Sato
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
- Laboratory for Mechanistic Chemistry of Biomolecules, Department of Chemistry, Keio University, Yokohama, Japan
| | - Tomoko Ohta
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
| | - Yuri Morikawa
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
| | - Ayumu Konno
- Department of Neurophysiology & Neural Repair, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Hirokazu Hirai
- Department of Neurophysiology & Neural Repair, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Yuki Kurauchi
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
| | - Akinori Hisatsune
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
| | - Hiroshi Katsuki
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
| | - Takahiro Seki
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
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Seki T. [Exploration of preventive drugs for spinocerebellar ataxia using cultured cerebellar Purkinje cells]. Nihon Yakurigaku Zasshi 2019; 154:310-314. [PMID: 31787682 DOI: 10.1254/fpj.154.310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Neurodegenerative diseases are caused by progressive degeneration of specific neurons. To overcome neurodegenerative diseases, the exploitation of preventive drugs is strongly expected, since impaired neurons are not regenerated by drugs. Spinocerebellar ataxia (SCA) is a group of dominantly inherited neurodegenerative diseases and is characterized by the progressive cerebellar ataxia. To date, SCA is classified into SCA1-48 by the variance of causal genes. Since SCA patients are commonly characterized by cerebellar ataxia and atrophy of cerebellum, it is possible that there are common pathogenic mechanisms in SCAs. However, there are not any shared functions among SCA-causing proteins. Cerebellar Purkinje cells (PCs) are sole output neurons from cerebellar cortexes, crucial for cerebellar functions and characterized highly branched dendrites. During the exploration of the molecular pathogenesis of several SCA-causing proteins, we found that several SCA-causing proteins commonly trigger the impairment of dendritic development of primary cultured cerebellar PCs. Dendritic shrinkage of cerebellar PCs has been observed and is considered to be related to the motor dysfunction in several SCA model mice. Therefore, we assume that impaired dendritic development of cultured cerebellar Purkinje cells is one of the common phenotypes of SCA in vitro and that cultured PCs expressing SCA-causing proteins could be in vitro SCA models. This SCA model would be useful for the efficient exploration of novel preventive drugs against various types of SCAs.
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Affiliation(s)
- Takahiro Seki
- Department of Chemico-Pharmacological Science, Graduate School of Pharmaceutical Sciences, Kumamoto University
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4
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Spinocerebellar ataxia type 14 caused by a nonsense mutation in the PRKCG gene. Mol Cell Neurosci 2019; 98:46-53. [PMID: 31158466 DOI: 10.1016/j.mcn.2019.05.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/25/2019] [Accepted: 05/30/2019] [Indexed: 12/15/2022] Open
Abstract
Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant neurodegenerative disorder characterized by cerebellar ataxia with myoclonus, dystonia, spasticity, and rigidity. Although missense mutations and a deletion mutation have been found in the protein kinase C gamma (PRKCG) gene encoding protein kinase C γ (PKCγ) in SCA14 families, a nonsense mutation has not been reported. The patho-mechanisms underlying SCA14 remain poorly understood. However, gain-of-function mechanisms and loss-of-function mechanisms, but not dominant negative mechanisms, were reported the patho-mechanism of SCA14. We identified the c.226C>T mutation of PRKCG, which caused the p.R76X in PKCγ by whole-exome sequencing in patients presenting cerebellar atrophy with cognitive and hearing impairment. To investigate the patho-mechanism of our case, we studied aggregation formation, cell death, and PKC inhibitory effect by confocal microscopy, western blotting with cleaved caspase 3, and pSer PKC motif antibodies, respectively. PKCγ(R76X)-GFP have aggregations the same as wild-type (WT) PKCγ-GFP. The PKCγ(R76X)-GFP inhibited PKC phosphorylation activity more than GFP alone. It also induced more apoptosis in COS7 and SH-SY5Y cells compared to WT-PKCγ-GFP and GFP. We first reported SCA14 patients with p.R76X in PKCγ who have cerebellar atrophy with cognitive and hearing impairment. Our results suggest that a dominant negative mechanism due to truncated peptides produced by p.R76X may be at least partially responsible for the cerebellar atrophy.
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Nakazono A, Adachi N, Takahashi H, Seki T, Hamada D, Ueyama T, Sakai N, Saito N. Pharmacological induction of heat shock proteins ameliorates toxicity of mutant PKCγ in spinocerebellar ataxia type 14. J Biol Chem 2018; 293:14758-14774. [PMID: 30093405 DOI: 10.1074/jbc.ra118.002913] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 07/26/2018] [Indexed: 11/06/2022] Open
Abstract
Amyloid and amyloid-like protein aggregations are hallmarks of multiple, varied neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. We previously reported that spinocerebellar ataxia type 14 (SCA14), a dominant-inherited neurodegenerative disease that affects cerebellar Purkinje cells, is characterized by the intracellular formation of neurotoxic amyloid-like aggregates of genetic variants of protein kinase Cγ (PKCγ). A number of protein chaperones, including heat shock protein 70 (Hsp70), promote the degradation and/or refolding of misfolded proteins and thereby prevent their aggregation. Here, we report that, in various SCA14-associated, aggregating PKCγ variants, endogenous Hsp70 is incorporated into aggregates and that expression of these PKCγ mutants up-regulates Hsp70 expression. We observed that PKCγ binds Hsp70 and that this interaction is enhanced in the SCA14-associated variants, mediated by the kinase domain that is involved in amyloid-like fibril formation as well as the C2 domain of PKCγ. Pharmacological up-regulation of Hsp70 by the Hsp90 inhibitors celastrol and herbimycin A attenuated the aggregation of mutant PKCγ in primary cultured Purkinje cells. Up-regulation of Hsp70 diminished net PKCγ aggregation by preventing aggregate formation, resulting in decreased levels of apoptotic cell death among primary cultured Purkinje cells expressing the PKCγ variant. Of note, herbimycin A also ameliorated abnormal dendritic development. Extending our in vitro observations, administration of celastrol to mice up-regulated cerebellar Hsp70. Our findings identify heat shock proteins as important endogenous regulators of pathophysiological PKCγ aggregation and point to Hsp90 inhibition as a potential therapeutic strategy in the treatment of SCA14.
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Affiliation(s)
- Aoi Nakazono
- From the Biosignal Research Center, Kobe University, Kobe 657-8501
| | - Naoko Adachi
- From the Biosignal Research Center, Kobe University, Kobe 657-8501,
| | | | - Takahiro Seki
- the Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973
| | - Daizo Hamada
- the Graduate School of Engineering and.,Center for Applied Structural Science (CASS), Kobe University, 7-1-48 Minatojima Minami Machi, Chuo-ku, Kobe 650-0047, and
| | - Takehiko Ueyama
- From the Biosignal Research Center, Kobe University, Kobe 657-8501
| | - Norio Sakai
- the Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical Science, Hiroshima University, Hiroshima 734-8551, Japan
| | - Naoaki Saito
- From the Biosignal Research Center, Kobe University, Kobe 657-8501,
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6
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Type 1 metabotropic glutamate receptor and its signaling molecules as therapeutic targets for the treatment of cerebellar disorders. Curr Opin Pharmacol 2018. [DOI: 10.1016/j.coph.2018.02.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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7
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Liu S, Dai Q, Hua R, Liu T, Han S, Li S, Li J. Determination of Brain-Regional Blood Perfusion and Endogenous cPKCγ Impact on Ischemic Vulnerability of Mice with Global Ischemia. Neurochem Res 2017; 42:2814-2825. [DOI: 10.1007/s11064-017-2294-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 04/19/2017] [Accepted: 05/06/2017] [Indexed: 01/12/2023]
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8
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Transduction Profile of the Marmoset Central Nervous System Using Adeno-Associated Virus Serotype 9 Vectors. Mol Neurobiol 2016; 54:1745-1758. [DOI: 10.1007/s12035-016-9777-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 02/03/2016] [Indexed: 01/22/2023]
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9
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Seki T. [Fluorescence-based method to assess the activity of chaperone-mediated autophagy]. Nihon Yakurigaku Zasshi 2015; 145:206-10. [PMID: 25864832 DOI: 10.1254/fpj.145.206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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10
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Takahashi H, Adachi N, Shirafuji T, Danno S, Ueyama T, Vendruscolo M, Shuvaev AN, Sugimoto T, Seki T, Hamada D, Irie K, Hirai H, Sakai N, Saito N. Identification and characterization of PKCγ, a kinase associated with SCA14, as an amyloidogenic protein. Hum Mol Genet 2015; 24:525-39. [PMID: 25217572 DOI: 10.1093/hmg/ddu472] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Amyloid assemblies are associated with a wide range of human disorders, including Alzheimer's and Parkinson's diseases. Here, we identify protein kinase C (PKC) γ, a serine/threonine kinase mutated in the neurodegenerative disease spinocerebellar ataxia type 14 (SCA14), as a novel amyloidogenic protein with no previously characterized amyloid-prone domains. We found that overexpression of PKCγ in cultured cells, as well as in vitro incubation of PKCγ without heat or chemical denaturants, causes amyloid-like fibril formation of this protein. We also observed that SCA14-associated mutations in PKCγ accelerate the amyloid-like fibril formation both in cultured cells and in vitro. We show that the C1A and kinase domains of PKCγ are involved in its soluble dimer and aggregate formation and that SCA14-associated mutations in the C1 domain cause its misfolding and aggregation. Furthermore, long-term time-lapse imaging indicates that aggregates of mutant PKCγ are highly toxic to neuronal cells. Based on these findings, we propose that PKCγ could form amyloid-like fibrils in physiological and/or pathophysiological conditions such as SCA14. More generally, our results provide novel insights into the mechanism of amyloid-like fibril formation by multi-domain proteins.
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Affiliation(s)
| | - Naoko Adachi
- Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
| | | | - Sally Danno
- Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
| | - Takehiko Ueyama
- Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
| | - Michele Vendruscolo
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Anton N Shuvaev
- Department of Neurophysiology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Takuya Sugimoto
- Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Takahiro Seki
- Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Daizo Hamada
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan and
| | - Kazuhiro Irie
- Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Hirokazu Hirai
- Department of Neurophysiology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Norio Sakai
- Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical Science, Hiroshima University, Hiroshima 734-8551, Japan
| | - Naoaki Saito
- Biosignal Research Center, Kobe University, Kobe 657-8501, Japan
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11
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Subramony S, Moscovich M, Ashizawa T. Genetics and Clinical Features of Inherited Ataxias. Mov Disord 2015. [DOI: 10.1016/b978-0-12-405195-9.00062-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Yamamoto K, Seki T, Yamamoto H, Adachi N, Tanaka S, Hide I, Saito N, Sakai N. Deregulation of the actin cytoskeleton and macropinocytosis in response to phorbol ester by the mutant protein kinase C gamma that causes spinocerebellar ataxia type 14. Front Physiol 2014; 5:126. [PMID: 24744737 PMCID: PMC3978357 DOI: 10.3389/fphys.2014.00126] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 03/13/2014] [Indexed: 11/14/2022] Open
Abstract
Several missense mutations in the protein kinase Cγ (γPKC) gene have been found to cause spinocerebellar ataxia type 14 (SCA14), an autosomal dominant neurodegenerative disease. γPKC is a neuron-specific member of the classical PKCs and is activated and translocated to subcellular regions as a result of various stimuli, including diacylglycerol synthesis, increased intracellular Ca2+ and phorbol esters. We investigated whether SCA14 mutations affect the γPKC-related functions by stimulating HeLa cells with TPA (12-O-tetradecanoylpholbol 13-acetate), a type of phorbol ester. Wild-type (WT) γPKC-GFP was translocated to the plasma membrane within 10 min of TPA stimulation, followed by its perinuclear translocation and cell shrinkage, in a PKC kinase activity- and microtubule-dependent manner. On the other hand, although SCA14 mutant γPKC-GFP exhibited a similar translocation to the plasma membrane, the subsequent perinuclear translocation and cell shrinkage were significantly impaired in response to TPA. Translocated WT γPKC colocalized with F-actin and formed large vesicular structures in the perinuclear region. The uptake of FITC-dextran, a marker of macropinocytosis, was promoted by TPA stimulation in cells expressing WT γPKC, and FITC-dextran was surrounded by γPKC-positive vesicles. Moreover, TPA induced the phosphorylation of MARCKS, which is a membrane-substrate of PKC, resulting in the translocation of phosphorylated MARCKS to the perinuclear region, suggesting that TPA induces macropinocytosis via γPKC activation. However, TPA failed to activate macropinocytosis and trigger the translocation of phosphorylated MARCKS in cells expressing the SCA14 mutant γPKC. These findings suggest that γPKC is involved in the regulation of the actin cytoskeleton and macropinocytosis in HeLa cells, while SCA14 mutant γPKC fails to regulate these processes due to its reduced kinase activity at the plasma membrane. This property might be involved in pathogenesis of SCA14.
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Affiliation(s)
- Kazuhiro Yamamoto
- Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University Hiroshima, Japan
| | - Takahiro Seki
- Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University Hiroshima, Japan ; Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University Kumamoto, Japan
| | - Hikaru Yamamoto
- Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University Hiroshima, Japan ; Biosignal Research Center, Kobe University Kobe, Japan
| | - Naoko Adachi
- Biosignal Research Center, Kobe University Kobe, Japan
| | - Shigeru Tanaka
- Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University Hiroshima, Japan
| | - Izumi Hide
- Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University Hiroshima, Japan
| | - Naoaki Saito
- Biosignal Research Center, Kobe University Kobe, Japan
| | - Norio Sakai
- Department of Molecular and Pharmacological Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University Hiroshima, Japan
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Mutant γPKC that causes spinocerebellar ataxia type 14 upregulates Hsp70, which protects cells from the mutant's cytotoxicity. Biochem Biophys Res Commun 2013; 440:25-30. [PMID: 24021284 DOI: 10.1016/j.bbrc.2013.09.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 09/02/2013] [Indexed: 11/24/2022]
Abstract
Several missense mutations in the protein kinase Cγ (γPKC) gene have been found to cause spinocerebellar ataxia type 14 (SCA14), an autosomal dominant neurodegenerative disease. We previously demonstrated that the mutant γPKC found in SCA14 is misfolded, susceptible to aggregation and cytotoxic. Molecular chaperones assist the refolding and degradation of misfolded proteins and prevention of the proteins' aggregation. In the present study, we found that the expression of mutant γPKC-GFP increased the levels of heat-shock protein 70 (Hsp70) in SH-SY5Y cells. To elucidate the role of this elevation, we investigated the effect of siRNA-mediated knockdown of Hsp70 on the aggregation and cytotoxicity of mutant γPKC. Knockdown of Hsp70 exacerbated the aggregation and cytotoxicity of mutant γPKC-GFP by inhibiting this mutant's degradation. These findings suggest that mutant γPKC increases the level of Hsp70, which protects cells from the mutant's cytotoxicity by enhancing its degradation.
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Thomanetz V, Angliker N, Cloëtta D, Lustenberger RM, Schweighauser M, Oliveri F, Suzuki N, Rüegg MA. Ablation of the mTORC2 component rictor in brain or Purkinje cells affects size and neuron morphology. ACTA ACUST UNITED AC 2013; 201:293-308. [PMID: 23569215 PMCID: PMC3628512 DOI: 10.1083/jcb.201205030] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The mTOR complex 2 (mTORC2) is essential in the central nervous system for normal neuronal structure and function, potentially through effects on PKC signaling and independent of the related mTOR complex 1 (mTORC1). The mammalian target of rapamycin (mTOR) assembles into two distinct multi-protein complexes called mTORC1 and mTORC2. Whereas mTORC1 is known to regulate cell and organismal growth, the role of mTORC2 is less understood. We describe two mouse lines that are devoid of the mTORC2 component rictor in the entire central nervous system or in Purkinje cells. In both lines neurons were smaller and their morphology and function were strongly affected. The phenotypes were accompanied by loss of activation of Akt, PKC, and SGK1 without effects on mTORC1 activity. The striking decrease in the activation and expression of several PKC isoforms, the subsequent loss of activation of GAP-43 and MARCKS, and the established role of PKCs in spinocerebellar ataxia and in shaping the actin cytoskeleton strongly suggest that the morphological deficits observed in rictor-deficient neurons are mediated by PKCs. Together our experiments show that mTORC2 has a particularly important role in the brain and that it affects size, morphology, and function of neurons.
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