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Carrettiero DC, Almeida MC, Longhini AP, Rauch JN, Han D, Zhang X, Najafi S, Gestwicki JE, Kosik KS. Stress routes clients to the proteasome via a BAG2 ubiquitin-independent degradation condensate. Nat Commun 2022; 13:3074. [PMID: 35654899 PMCID: PMC9163039 DOI: 10.1038/s41467-022-30751-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 05/16/2022] [Indexed: 02/06/2023] Open
Abstract
The formation of membraneless organelles can be a proteotoxic stress control mechanism that locally condenses a set of components capable of mediating protein degradation decisions. The breadth of mechanisms by which cells respond to stressors and form specific functional types of membraneless organelles, is incompletely understood. We found that Bcl2-associated athanogene 2 (BAG2) marks a distinct phase-separated membraneless organelle, triggered by several forms of stress, particularly hyper-osmotic stress. Distinct from well-known condensates such as stress granules and processing bodies, BAG2-containing granules lack RNA, lack ubiquitin and promote client degradation in a ubiquitin-independent manner via the 20S proteasome. These organelles protect the viability of cells from stress and can traffic to the client protein, in the case of Tau protein, on the microtubule. Components of these ubiquitin-independent degradation organelles include the chaperone HSP-70 and the 20S proteasome activated by members of the PA28 (PMSE) family. BAG2 condensates did not co-localize with LAMP-1 or p62/SQSTM1. When the proteasome is inhibited, BAG2 condensates and the autophagy markers traffic to an aggresome-like structure.
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Affiliation(s)
- Daniel C Carrettiero
- Neuroscience Research Institute, Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA, USA
- Center for Natural and Human Sciences, Federal University of ABC, São Bernardo do Campo, SP, Brazil
| | - Maria C Almeida
- Neuroscience Research Institute, Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA, USA
- Center for Natural and Human Sciences, Federal University of ABC, São Bernardo do Campo, SP, Brazil
| | - Andrew P Longhini
- Neuroscience Research Institute, Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Jennifer N Rauch
- Neuroscience Research Institute, Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Dasol Han
- Neuroscience Research Institute, Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Xuemei Zhang
- Neuroscience Research Institute, Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA, USA
| | - Saeed Najafi
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
| | - Jason E Gestwicki
- Institute for Neurodegenerative Disease, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA, USA
| | - Kenneth S Kosik
- Neuroscience Research Institute, Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA, USA.
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Lima RS, Carrettiero DC, Ferrari MFR. BAG2 prevents Tau hyperphosphorylation and increases p62/SQSTM1 in cell models of neurodegeneration. Mol Biol Rep 2022; 49:7623-7635. [PMID: 35612780 DOI: 10.1007/s11033-022-07577-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 05/06/2022] [Indexed: 11/29/2022]
Abstract
BACKGROUND Protein aggregates are pathological hallmarks of many neurodegenerative diseases, however the physiopathological role of these aggregates is not fully understood. Protein quality control has a pivotal role for protein homeostasis and depends on specific chaperones. The co-chaperone BAG2 can target phosphorylated Tau for degradation by an ubiquitin-independent pathway, although its possible role in autophagy was not yet elucidated. In view of this, the aim of the present study was to investigate the association among protein aggregation, autophagy and BAG2 levels in cultured cells from hippocampus and locus coeruleus as well as in SH-SY5Y cell line upon different protein aggregation scenarios induced by rotenone, which is a flavonoid used as pesticide and triggers neurodegeneration. METHODS AND RESULTS The present study showed that rotenone exposure at 0.3 nM for 48 h impaired autophagy prior to Tau phosphorylation at Ser199/202 in hippocampus but not in locus coeruleus cells, suggesting that distinct neuron cells respond differently to rotenone toxicity. Rotenone induced Tau phosphorylation at Ser199/202, together with a decrease in the endogenous BAG2 protein levels in SH-SY5Y and hippocampus cell culture, which indicates that rotenone and Tau hyperphosphorylation can affect this co-chaperone. Finally, it has been shown that BAG2 overexpression, increased p62/SQSTM1 levels in cells from hippocampus and locus coeruleus, stimulated LC3II recycling as well as prevented the raise of phosphorylated Tau at Ser199/202 in hippocampus. CONCLUSIONS Results demonstrate a possible role for BAG2 in degradation pathways of specific substrates and its importance for the study of cellular aspects of neurodegenerative diseases.
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Affiliation(s)
- Raquel S Lima
- Departamento de Genetica e Biologia Evolutiva, Instituto de Biociencias, Universidade de Sao Paulo, Rua do Matao, 277, Cidade Universitaria, Sao Paulo, SP, 05508-090, Brazil
| | - Daniel C Carrettiero
- Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Santo Andre, SP, Brazil
| | - Merari F R Ferrari
- Departamento de Genetica e Biologia Evolutiva, Instituto de Biociencias, Universidade de Sao Paulo, Rua do Matao, 277, Cidade Universitaria, Sao Paulo, SP, 05508-090, Brazil.
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3
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Shi Y, Yuan J, Rraklli V, Maxymovitz E, Cipullo M, Liu M, Li S, Westerlund I, Bedoya-Reina OC, Bullova P, Rorbach J, Juhlin CC, Stenman A, Larsson C, Kogner P, O’Sullivan MJ, Schlisio S, Holmberg J. Aberrant splicing in neuroblastoma generates RNA-fusion transcripts and provides vulnerability to spliceosome inhibitors. Nucleic Acids Res 2021; 49:2509-2521. [PMID: 33555349 PMCID: PMC7969022 DOI: 10.1093/nar/gkab054] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 01/14/2021] [Accepted: 01/21/2021] [Indexed: 11/12/2022] Open
Abstract
The paucity of recurrent mutations has hampered efforts to understand and treat neuroblastoma. Alternative splicing and splicing-dependent RNA-fusions represent mechanisms able to increase the gene product repertoire but their role in neuroblastoma remains largely unexplored. Here we investigate the presence and possible roles of aberrant splicing and splicing-dependent RNA-fusion transcripts in neuroblastoma. In addition, we attend to establish whether the spliceosome can be targeted to treat neuroblastoma. Through analysis of RNA-sequenced neuroblastoma we show that elevated expression of splicing factors is a strong predictor of poor clinical outcome. Furthermore, we identified >900 primarily intrachromosomal fusions containing canonical splicing sites. Fusions included transcripts from well-known oncogenes, were enriched for proximal genes and in chromosomal regions commonly gained or lost in neuroblastoma. As a proof-of-principle that these fusions can generate altered gene products, we characterized a ZNF451-BAG2 fusion, producing a truncated BAG2-protein which inhibited retinoic acid induced differentiation. Spliceosome inhibition impeded neuroblastoma fusion expression, induced apoptosis and inhibited xenograft tumor growth. Our findings elucidate a splicing-dependent mechanism generating altered gene products in neuroblastoma and show that the spliceosome is a potential target for clinical intervention.
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Affiliation(s)
- Yao Shi
- Department of Cell and Molecular Biology, Karolinska Institutet, Solnavägen 9, SE-171 65 Stockholm, Sweden
| | - Juan Yuan
- Department of Cell and Molecular Biology, Karolinska Institutet, Solnavägen 9, SE-171 65 Stockholm, Sweden
| | - Vilma Rraklli
- Department of Cell and Molecular Biology, Karolinska Institutet, Solnavägen 9, SE-171 65 Stockholm, Sweden
| | - Eva Maxymovitz
- Department of Cell and Molecular Biology, Karolinska Institutet, Solnavägen 9, SE-171 65 Stockholm, Sweden
| | - Miriam Cipullo
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Solnavägen 9, SE-171-65 Solna, Sweden
| | - Mingzhi Liu
- Department of Cell and Molecular Biology, Karolinska Institutet, Solnavägen 9, SE-171 65 Stockholm, Sweden
| | - Shuijie Li
- Department of Microbiology, Tumor- and Cellbiology, Karolinska Institutet, Solnavägen 9, SE-171 65 Solna, Sweden
| | - Isabelle Westerlund
- Department of Cell and Molecular Biology, Karolinska Institutet, Solnavägen 9, SE-171 65 Stockholm, Sweden
| | - Oscar C Bedoya-Reina
- Department of Microbiology, Tumor- and Cellbiology, Karolinska Institutet, Solnavägen 9, SE-171 65 Solna, Sweden
| | - Petra Bullova
- Department of Microbiology, Tumor- and Cellbiology, Karolinska Institutet, Solnavägen 9, SE-171 65 Solna, Sweden
| | - Joanna Rorbach
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Solnavägen 9, SE-171-65 Solna, Sweden
| | - C Christofer Juhlin
- Department of Oncology-Pathology, Karolinska Institutet, Cancer Center Karolinska (CCK), Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | - Adam Stenman
- Department of Oncology-Pathology, Karolinska Institutet, Cancer Center Karolinska (CCK), Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | - Catharina Larsson
- Department of Oncology-Pathology, Karolinska Institutet, Cancer Center Karolinska (CCK), Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | - Per Kogner
- Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | - Maureen J O’Sullivan
- Department of Histopathology, Our Lady's Children's Hospital, Dublin, Ireland
- Trinity Translational Medicine Institute, Trinity College, Dublin, Ireland
| | - Susanne Schlisio
- Department of Microbiology, Tumor- and Cellbiology, Karolinska Institutet, Solnavägen 9, SE-171 65 Solna, Sweden
| | - Johan Holmberg
- Department of Cell and Molecular Biology, Karolinska Institutet, Solnavägen 9, SE-171 65 Stockholm, Sweden
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4
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Qi J, Jia Y, Wang W, Lu H, Wang Y, Li Z. The role of Bag2 in neurotoxicity induced by the anesthetic sevoflurane. J Cell Biochem 2019; 120:7551-7559. [PMID: 30548665 DOI: 10.1002/jcb.28029] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Accepted: 10/15/2018] [Indexed: 01/24/2023]
Abstract
Sevoflurane is the most commonly used general anesthetic in pediatric patients. But preclinical studies indicate that sevoflurane could have neurotoxicity in newborn and old animals, and this raises concern regarding its safety. In this study, we explored the potential mechanisms of sevoflurane-induced neurotoxicity in human SH-SY5Y neuronal cells. We showed that prolonged exposure to 2% sevoflurane caused a significant increase in the Bag family protein Bag2 in a time- and dose-dependent manner. We investigated the possible role of Bag2 upon exposure to sevoflurane by silencing Bag2 in neuronal cells. Knockdown of Bag2 caused increased overall reactive oxygen species (ROS) and generation of lipid peroxidation products 4-hydroxynonenal (4-HNE). Upon sevoflurane exposure, Bag2-silent cells have reduced glutathione (GSH) and glutathione peroxidase activity. Under the sevoflurane treatment, Bag2-deficient cells have reduced mitochondrial membrane potential (MMP) and adenosine triphosphate (ATP) production, while knockdown cells have less viability and higher lactic dehydrogenase (LDH) release as well as a higher percentage of apoptotic cells. The knockdown cells also had higher levels of mitochondrial cytochrome C release, a higher ratio of Bax/Bcl-2 and increased caspase cleavage by sevoflurane. Overall, our data support an important role of Bag2 in sevoflurane-induced neurotoxicity.
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Affiliation(s)
- Jinlian Qi
- Department of anesthesiology, Henan Children's Hospital.,Department of anesthesiology, Zhengzhou Children's Hospital.,Department of Anesthesiology, Childern's Hospital Affiliated of Zhengzhou University, Zhengzhou, China
| | - Yingping Jia
- Department of anesthesiology, Henan Children's Hospital.,Department of anesthesiology, Zhengzhou Children's Hospital.,Department of Anesthesiology, Childern's Hospital Affiliated of Zhengzhou University, Zhengzhou, China
| | - Wenhua Wang
- Department of anesthesiology, Henan Children's Hospital.,Department of anesthesiology, Zhengzhou Children's Hospital.,Department of Anesthesiology, Childern's Hospital Affiliated of Zhengzhou University, Zhengzhou, China
| | - Haibing Lu
- Department of anesthesiology, Henan Children's Hospital.,Department of anesthesiology, Zhengzhou Children's Hospital.,Department of Anesthesiology, Childern's Hospital Affiliated of Zhengzhou University, Zhengzhou, China
| | - Yuan Wang
- Department of anesthesiology, Henan Children's Hospital.,Department of anesthesiology, Zhengzhou Children's Hospital.,Department of Anesthesiology, Childern's Hospital Affiliated of Zhengzhou University, Zhengzhou, China
| | - Zhengchen Li
- Department of anesthesiology, Henan Children's Hospital.,Department of anesthesiology, Zhengzhou Children's Hospital.,Department of Anesthesiology, Childern's Hospital Affiliated of Zhengzhou University, Zhengzhou, China
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5
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Moreira-Silva D, Carrettiero DC, Oliveira ASA, Rodrigues S, Dos Santos-Lopes J, Canas PM, Cunha RA, Almeida MC, Ferreira TL. Anandamide Effects in a Streptozotocin-Induced Alzheimer's Disease-Like Sporadic Dementia in Rats. Front Neurosci 2018; 12:653. [PMID: 30333717 PMCID: PMC6176656 DOI: 10.3389/fnins.2018.00653] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 08/30/2018] [Indexed: 12/21/2022] Open
Abstract
Alzheimer's disease (AD) is characterized by multiple cognitive deficits including memory and sensorimotor gating impairments as a result of neuronal and synaptic loss. The endocannabinoid system plays an important role in these deficits but little is known about its influence on the molecular mechanism regarding phosphorylated tau (p-tau) protein accumulation - one of the hallmarks of AD -, and on the density of synaptic proteins. Thus, the aim of this study was to investigate the preventive effects of anandamide (N-arachidonoylethanolamine, AEA) on multiple cognitive deficits and on the levels of synaptic proteins (syntaxin 1, synaptophysin and synaptosomal-associated protein, SNAP-25), cannabinoid receptor type 1 (CB1) and molecules related to p-tau degradation machinery (heat shock protein 70, HSP70), and Bcl2-associated athanogene (BAG2) in an AD-like sporadic dementia model in rats using intracerebroventricular (icv) injection of streptozotocin (STZ). Our hypothesis is that AEA could interact with HSP70, modulating the level of p-tau and synaptic proteins, preventing STZ-induced cognitive impairments. Thirty days after receiving bilateral icv injections of AEA or STZ or both, the cognitive performance of adult male Wistar rats was evaluated in the object recognition test, by the escape latency in the elevated plus maze (EPM), by the tone and context fear conditioning as well as in prepulse inhibition tests. Subsequently, the animals were euthanized and their brains were removed for histological analysis or for protein quantification by Western Blotting. The behavioral results showed that STZ impaired recognition, plus maze and tone fear memories but did not affect contextual fear memory and prepulse inhibition. Moreover, AEA prevented recognition and non-associative emotional memory impairments induced by STZ, but did not influence tone fear conditioning. STZ increased the brain ventricular area and this enlargement was prevented by AEA. Additionally, STZ reduced the levels of p-tau (Ser199/202) and increased p-tau (Ser396), although AEA did not affect these alterations. HSP70 was found diminished only by STZ, while BAG2 levels were decreased by STZ and AEA. Synaptophysin, syntaxin and CB1 receptor levels were reduced by STZ, but only syntaxin was recovered by AEA. Altogether, albeit AEA failed to modify some AD-like neurochemical alterations, it partially prevented STZ-induced cognitive impairments, changes in synaptic markers and ventricle enlargement. This study showed, for the first time, that the administration of an endocannabinoid can prevent AD-like effects induced by STZ, boosting further investigations about the modulation of endocannabinoid levels as a therapeutic approach for AD.
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Affiliation(s)
- Daniel Moreira-Silva
- Center for Mathematics, Computing and Cognition, Universidade Federal do ABC, São Bernardo do Campo, Brazil
| | - Daniel C Carrettiero
- Center for Natural and Human Sciences, Universidade Federal do ABC, São Bernardo do Campo, Brazil
| | - Adriele S A Oliveira
- Center for Natural and Human Sciences, Universidade Federal do ABC, São Bernardo do Campo, Brazil
| | - Samanta Rodrigues
- Center for Mathematics, Computing and Cognition, Universidade Federal do ABC, São Bernardo do Campo, Brazil
| | - Joyce Dos Santos-Lopes
- Center for Mathematics, Computing and Cognition, Universidade Federal do ABC, São Bernardo do Campo, Brazil
| | - Paula M Canas
- Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal
| | - Rodrigo A Cunha
- Faculty of Medicine, University of Coimbra, Coimbra, Portugal.,Center for Neuroscience and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal
| | - Maria C Almeida
- Center for Natural and Human Sciences, Universidade Federal do ABC, São Bernardo do Campo, Brazil
| | - Tatiana L Ferreira
- Center for Mathematics, Computing and Cognition, Universidade Federal do ABC, São Bernardo do Campo, Brazil
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6
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Qin L, Guo J, Zheng Q, Zhang H. BAG2 structure, function and involvement in disease. Cell Mol Biol Lett 2016; 21:18. [PMID: 28536620 PMCID: PMC5415834 DOI: 10.1186/s11658-016-0020-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 09/10/2016] [Indexed: 12/30/2022] Open
Abstract
Bcl2-associated athanogene 2 (BAG2) shares a similar molecular structure and function with other BAG family members. Functioning as a co-chaperone, it interacts with the ATPase domain of the heat shock protein 70 (dHsp70) through its BAG domain. It also interacts with many other molecules and regulates various cellular functions. An increasing number of studies have indicated that BAG2 is involved in the pathogenesis of various diseases, including cancers and neurodegenerative diseases. This paper is a comprehensive review of the structure, functions, and protein interactions of BAG2. We also discuss its roles in diseases, including cancer, Alzheimer's disease, Parkinson's disease and spinocerebellar ataxia type-3. Further research on BAG2 could lead to an understanding of the pathogenesis of these disorders or even to novel therapeutic approaches.
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Affiliation(s)
- Lixia Qin
- Department of Neurology, The Second Xiangya Hospital, Central South University, Changsha, China.,Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Jifeng Guo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Qian Zheng
- Department of Neurology, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Hainan Zhang
- Department of Neurology, The Second Xiangya Hospital, Central South University, Changsha, China
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Noel A, Barrier L, Ingrand S. The Tyr216 phosphorylated form of GSK3β contributes to tau phosphorylation at PHF-1 epitope in response to Aβ in the nucleus of SH-SY5Y cells. Life Sci 2016; 158:14-21. [PMID: 27343974 DOI: 10.1016/j.lfs.2016.06.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 06/09/2016] [Accepted: 06/20/2016] [Indexed: 12/21/2022]
Abstract
AIMS GSK3β activation in Aβ conditions leading to tau phosphorylation at pathological sites is a well-known phenomenon. However, the serine/tyrosine phosphorylation processes implied in Aβ-induced GSK3β activation and responsible for tau phosphorylation, especially at the GSK3β specific Ser396/Ser404 (PHF-1) site, are still debated. MAIN METHODS Experiments were performed on SH-SY5Y cells exposed to 20μM Aβ1-42 in a time ranging from 5min to 8h. The phophorylated forms (Ser9 and Tyr216) of GSK3β and pTau at PHF-1 epitope were measured by immunoblotting in nuclear extracts. KEY FINDINGS We showed a superimposable time-dependent increase of nuclear pGSK3βTyr216 and nuclear pTau at PHF-1 site, both reaching their maximal level after 8h of Aβ1-42 exposure. In addition, nuclear accumulation of pTau is accompanied by its cytoplasmic decrease suggesting that pTau is translocated in response to Aβ treatment. Besides, our experiments showed that specific pGSK3βTyr216 inhibition is required to drop nuclear pTau, ensuring the involvement of Tyr216 phosphorylation in Aβ-mediated tau phosphorylation at PHF-1 epitope. SIGNIFICANCE These data suggested that in response to Aβ exposure in SH-SY5Y cells, GSK3β activation is performed through Tyr216 phosphorylation and resulted in tau phosphorylation at PHF-1 epitope and in its translocation.
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Affiliation(s)
- Anastasia Noel
- Université de Poitiers, Groupe de Recherche sur le Vieillissement Cérébral, GRéViC, EA 3808, Poitiers, France
| | - Laurence Barrier
- Université de Poitiers, UFR Médecine&Pharmacie, Service de Biochimie et Toxicologie, 6 rue de la Milétrie, TSA 51115, 86073 Poitiers Cedex 9, France
| | - Sabrina Ingrand
- Université de Poitiers, UFR Médecine&Pharmacie, Service de Biochimie et Toxicologie, 6 rue de la Milétrie, TSA 51115, 86073 Poitiers Cedex 9, France.
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BAG2 expression dictates a functional intracellular switch between the p38-dependent effects of nicotine on tau phosphorylation levels via the α7 nicotinic receptor. Exp Neurol 2015; 275 Pt 1:69-77. [PMID: 26496817 DOI: 10.1016/j.expneurol.2015.10.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/25/2015] [Accepted: 10/19/2015] [Indexed: 01/03/2023]
Abstract
The histopathological hallmarks present in Alzheimer's disease (AD) brain are plaques of Aβ peptide, neurofibrillary tangles of hyperphosphorylated tau protein, and a reduction in nicotinic acetylcholine receptor (nAChR) levels. The role of nAChRs in AD is particularly controversial. Tau protein function is regulated by phosphorylation, and its hyperphosphorylated forms are significantly more abundant in AD brain. Little is known about the relationship between nAChR and phospho-tau degradation machinery. Activation of nAChRs has been reported to increase and decrease tau phosphorylation levels, and the mechanisms responsible for this discrepancy are not presently understood. The co-chaperone BAG2 is capable of regulating phospho-tau levels via protein degradation. In SH-SY5Y cell line and rat primary hippocampal cell culture low endogenous BAG2 levels constitute an intracellular environment conducive to nicotine-induced accumulation of phosphorylated tau protein. Further, nicotine treatment inhibited endogenous expression of BAG2, resulting in increased levels of phosphorylated tau indistinguishable from those induced by BAG2 knockdown. Conversely, overexpression of BAG2 is conducive to a nicotine-induced reduction in cellular levels of phosphorylated tau protein. In both cases the effect of nicotine was p38MAPK-dependent, while the α7 antagonist MLA was synthetic to nicotine treatment, either increasing levels of phospho-Tau in the absence of BAG2, or further decreasing the levels of phospho-Tau in the presence of BAG2. Taken together, these findings reconcile the apparently contradictory effects of nicotine on tau phosphorylation by suggesting a role for BAG2 as an important regulator of p38-dependent tau kinase activity and phospho-tau degradation in response to nicotinic receptor stimulation. Thus, we report that BAG2 expression dictates a functional intracellular switch between the p38-dependent functions of nicotine on tau phosphorylation levels via the α7 nicotinic receptor.
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9
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Carrettiero DC, Santiago FE, Motzko-Soares ACP, Almeida MC. Temperature and toxic Tau in Alzheimer's disease: new insights. Temperature (Austin) 2015; 2:491-8. [PMID: 27227069 PMCID: PMC4843920 DOI: 10.1080/23328940.2015.1096438] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 09/15/2015] [Accepted: 09/15/2015] [Indexed: 12/31/2022] Open
Abstract
Alzheimer's disease (AD), the most common dementia in the elderly, is characterized by cognitive impairment and severe autonomic symptoms such as disturbance in core body temperature (Tc), which may be predictors or early events in AD onset. Inclusions of phosphorylated Tau (p-Tau) are a hallmark of AD and other neurodegenerative disorders called “Tauopathies.” Animal and human studies show that anesthesia augments p-Tau levels through reduction of Tc, with implications for AD. Additionally, hypothermia impairs memory and cognitive function. The molecular networks related to Tc that are associated with AD remain poorly characterized. Under physiological conditions, Tau binds microtubules, promoting their assembly and stability. The dynamically regulated Tau-microtubule interaction plays an important role in structural remodeling of the cytoskeleton, having important functions in neuronal plasticity and memory in the hippocampus. Hypothermia-induced increases in p-Tau levels are significant, with an 80% increase for each degree Celsius below normothermic conditions. Although the effects of temperature on Tau phosphorylation are evident, its effects on p-Tau degradation remain poorly understoodWe review information concerning the mechanisms of Tau regulation of neuron plasticity via its effects on microtubule dynamics, with focus on pathways regulating the abundance of phosphorylated Tau species. We highlight the effects of temperature on molecular mechanisms influencing the development of Tau-related diseases. Specifically, we argue that cold might preferentially affects central nervous system structures that are highly reliant upon plasticity, such as the hippocampus, and that the effect of cold on Tau phosphorylation may constitute a pathology-initiating trigger leading to neurodegeneration.
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Affiliation(s)
- Daniel Carneiro Carrettiero
- Graduate Program in Neuroscience and Cognition; Universidade Federal do ABC; São Bernardo do Campo, Brasil; Center for Natural Sciences and Humanities; Universidade Federal do ABC; São Bernardo do Campo, Brasil
| | - Fernando Enrique Santiago
- Graduate Program in Neuroscience and Cognition; Universidade Federal do ABC; São Bernardo do Campo , Brasil
| | | | - Maria Camila Almeida
- Graduate Program in Neuroscience and Cognition; Universidade Federal do ABC; São Bernardo do Campo, Brasil; Center for Natural Sciences and Humanities; Universidade Federal do ABC; São Bernardo do Campo, Brasil
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