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Deane CAS, Brown IR. Components of a mammalian protein disaggregation/refolding machine are targeted to nuclear speckles following thermal stress in differentiated human neuronal cells. Cell Stress Chaperones 2017; 22:191-200. [PMID: 27966060 PMCID: PMC5352593 DOI: 10.1007/s12192-016-0753-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 11/25/2016] [Accepted: 11/25/2016] [Indexed: 01/19/2023] Open
Abstract
Heat shock proteins (Hsps) are a set of highly conserved proteins involved in cellular repair and protective mechanisms. They counter protein misfolding and aggregation that are characteristic features of neurodegenerative diseases. Hsps act co-operatively in disaggregation/refolding machines that assemble at sites of protein misfolding and aggregation. Members of the DNAJ (Hsp40) family act as "holdases" that detect and bind misfolded proteins, while members of the HSPA (Hsp70) family act as "foldases" that refold proteins to biologically active states. HSPH1 (Hsp105α) is an important additional member of the mammalian disaggregation/refolding machine that acts as a disaggregase to promote the dissociation of aggregated proteins. Components of a disaggregation/refolding machine were targeted to nuclear speckles after thermal stress in differentiated human neuronal SH-SY5Y cells, namely: HSPA1A (Hsp70-1), DNAJB1 (Hsp40-1), DNAJA1 (Hsp40-4), and HSPH1 (Hsp105α). Nuclear speckles are rich in RNA splicing factors, and heat shock disrupts RNA splicing which recovers after stressful stimuli. Interestingly, constitutively expressed HSPA8 (Hsc70) was also targeted to nuclear speckles after heat shock with elements of a disaggregation/refolding machine. Hence, neurons have the potential to rapidly assemble a disaggregation/refolding machine after cellular stress using constitutively expressed Hsc70 without the time lag needed for synthesis of stress-inducible Hsp70. Constitutive Hsc70 is abundant in neurons in the mammalian brain and has been proposed to play a role in pre-protecting neurons from cellular stress.
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Affiliation(s)
- Catherine A S Deane
- Centre for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada
| | - Ian R Brown
- Centre for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada.
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Gómez AV, Córdova G, Munita R, Parada GE, Barrios ÁP, Cancino GI, Álvarez AR, Andrés ME. Characterizing HSF1 Binding and Post-Translational Modifications of hsp70 Promoter in Cultured Cortical Neurons: Implications in the Heat-Shock Response. PLoS One 2015; 10:e0129329. [PMID: 26053851 PMCID: PMC4459960 DOI: 10.1371/journal.pone.0129329] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 05/08/2015] [Indexed: 11/21/2022] Open
Abstract
Causes of lower induction of Hsp70 in neurons during heat shock are still a matter of debate. To further inquire into the mechanisms regulating Hsp70 expression in neurons, we studied the activity of Heat Shock Factor 1 (HSF1) and histone posttranslational modifications (PTMs) at the hsp70 promoter in rat cortical neurons. Heat shock induced a transient and efficient translocation of HSF1 to neuronal nuclei. However, no binding of HSF1 at the hsp70 promoter was detected while it bound to the hsp25 promoter in cortical neurons during heat shock. Histone PTMs analysis showed that the hsp70 promoter harbors lower levels of histone H3 and H4 acetylation in cortical neurons compared to PC12 cells under basal conditions. Transcriptomic profiling data analysis showed a predominant usage of cryptic transcriptional start sites at hsp70 gene in the rat cerebral cortex, compared with the whole brain. These data support a weaker activation of hsp70 canonical promoter. Heat shock increased H3Ac at the hsp70 promoter in PC12 cells, which correlated with increased Hsp70 expression while no modifications occurred at the hsp70 promoter in cortical neurons. Increased histone H3 acetylation by Trichostatin A led to hsp70 mRNA and protein induction in cortical neurons. In conclusion, we found that two independent mechanisms maintain a lower induction of Hsp70 in cortical neurons. First, HSF1 fails to bind specifically to the hsp70 promoter in cortical neurons during heat shock and, second, the hsp70 promoter is less accessible in neurons compared to non-neuronal cells due to histone deacetylases repression.
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Affiliation(s)
- Andrea V. Gómez
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O’Higgins 340, Santiago, Chile
- * E-mail: (AVG); (MEA)
| | - Gonzalo Córdova
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O’Higgins 340, Santiago, Chile
| | - Roberto Munita
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O’Higgins 340, Santiago, Chile
| | - Guillermo E. Parada
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O’Higgins 340, Santiago, Chile
| | - Álvaro P. Barrios
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O’Higgins 340, Santiago, Chile
| | - Gonzalo I. Cancino
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O’Higgins 340, Santiago, Chile
| | - Alejandra R. Álvarez
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O’Higgins 340, Santiago, Chile
| | - María E. Andrés
- Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Av. Libertador Bernardo O’Higgins 340, Santiago, Chile
- * E-mail: (AVG); (MEA)
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Abstract
The expression of heat shock or stress proteins (hsps) is a widespread response to stress that results in the protection of cells from subsequent insults, coined stress tolerance. Stress tolerance is apparently due to the preservation of several cellular structures and processes, such as translation. Protection of protein synthesis has been correlated with the presence of Hsp70. In the present study, Hsp70 was found to interact with translating ribosomes. This interaction is due to the preferential binding of Hsp70 to the 40S ribosomal subunit. Additionally, Hsp70 seems to interact weakly with nascent polypeptides within the 60S subunit. The interaction between Hsp70 and ribosomal subunits could also be observed in vitro conditions. Binding of Hsp70 to ribosomes was salt resistant, suggesting that this protein is not bound to transiently associated translational factors. Moreover, protection of protein synthesis requires new gene expression. We speculate that the binding of Hsp70 to ribosomes is part of a mechanism to guarantee the rapid and abundant protein synthesis during stress, particularly the translation of mRNAs encoding for hsps.
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Affiliation(s)
- Lizbeth Cornivelli
- Department of Physiology, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA
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Gober MD, Smith CC, Ueda K, Toretsky JA, Aurelian L. Forced expression of the H11 heat shock protein can be regulated by DNA methylation and trigger apoptosis in human cells. J Biol Chem 2003; 278:37600-9. [PMID: 12832417 DOI: 10.1074/jbc.m303834200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
H11, the eukaryotic homologue of a herpes simplex virus protein, has the crystallin motif of heat shock proteins (Hsp), but it differs from canonical family members in that mRNA and protein levels were reduced in various tumor tissues and cell lines (viz. melanoma, prostate cancer and sarcoma) relative to their normal counterparts. In these cells, expression was not restored by heat shock, but rather by the demethylating agent 5-aza-2'-deoxycytidine (Aza-C). Forced H11 expression by Aza-C treatment, transient transfection with H11 expression vectors, or retrovirus-mediated delivery of H11 under the control of a tetracycline-sensitive promoter triggered apoptosis. This is evidenced by a significant (p < 0.001) increase in the percentage of cells positive for terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) and for activation of caspase-3 and p38MAPK and by the co-localization of TUNEL+ nuclei with increased H11 levels. Apoptosis was partially inhibited by the pancaspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone or the p38MAPK inhibitor SB203580. It was abrogated by co-treatment with both inhibitors, suggesting that H11-triggered apoptosis is both caspase- and p38MAPK-dependent. A single site mutant (H11-W51C) had cytoprotective activity related to MEK/ERK activation, and it blocked H11-induced apoptosis in co-transfected and Aza-C-treated cells, indicating that it is a dominant negative mutant. This is the first report of a heat shock protein with proapoptotic activity.
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Affiliation(s)
- Michael D Gober
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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Kaarniranta K, Oksala N, Karjalainen HM, Suuronen T, Sistonen L, Helminen HJ, Salminen A, Lammi MJ. Neuronal cells show regulatory differences in the hsp70 gene response. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2002; 101:136-40. [PMID: 12007842 DOI: 10.1016/s0169-328x(02)00179-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The synthesis of heat shock proteins (Hsps), encoded by heat shock genes, is increased in response to various stress stimuli. Hsps function as molecular chaperones, they dissociate cytotoxic stress-induced protein aggregates within cells and ensure improved survival. Induction of heat shock genes is mainly regulated at the transcriptional level. The stress responsive transcription factor, heat shock factor 1 (HSF1), is involved in the transcriptional induction of the heat shock genes. Our objective was to examine how hsp70 genes are regulated in different transformed and primary neurons upon exposure to elevated temperature. Our findings reveal that the Hsp70 response is regulated at the translational level in Neuro-2a neuroblastoma cells, while the IMR-32 neuroblastoma cells respond to stress by the classical HSF1-driven transcriptional regulatory mechanism. Primary rat hippocampal neurons show a lack of HSF1 and induction of the hsp70 gene. These observations suggest that neuronal cells display different hsp70 gene expression patterns which range from undetected response to transcriptional and posttranscriptional regulation during heat stress.
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Affiliation(s)
- K Kaarniranta
- Department of Anatomy, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland.
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Winklhofer KF, Reintjes A, Hoener MC, Voellmy R, Tatzelt J. Geldanamycin restores a defective heat shock response in vivo. J Biol Chem 2001; 276:45160-7. [PMID: 11574536 DOI: 10.1074/jbc.m104873200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Induced expression of heat shock proteins (Hsps) plays a central role in promoting cellular survival after environmental and physiological stress. We have previously shown that scrapie-infected mouse neuroblastoma (ScN2a) cells fail to induce the expression of Hsp72 and Hsp28 after various stress conditions. Here we present evidence that this impaired stress response is due to an altered regulation of HSF1 activity. Upon stress in ScN2a cells, HSF1 was converted into hyperphosphorylated trimers but failed to acquire transactivation competence. A kinetic analysis of HSF1 activation revealed that in ScN2a cells trimer formation after stress was efficient, but disassembly of trimers proceeded much faster than in the uninfected cell line. Geldanamycin, a Hsp90-binding drug, significantly delayed disassembly of HSF1 trimers after a heat shock and restored stress-induced expression of Hsp72 in ScN2a cells. Heat-induced Hsp72 expression required geldanamycin to be present; following removal of the drug ScN2a cells again lost their ability to mount a stress response. Thus, our studies show that a defective stress response can be pharmacologically restored and suggest that the HSF1 deactivation pathway may play an important role in the regulation of Hsp expression.
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Affiliation(s)
- K F Winklhofer
- Department of Cellular Biochemistry, Max-Planck-Institut für Biochemie and the Max-Planck-Institut für Neurobiologie, D-82152 Martinsried, Germany
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