Activation of heat shock factor 1 plays a role in pyrrolidine dithiocarbamate-mediated expression of the co-chaperone BAG3

Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
The international journal of biochemistry & cell biology (Impact Factor: 4.05). 11/2010; 42(11):1856-63. DOI: 10.1016/j.biocel.2010.07.021
Source: PubMed


Adaptive responses to physical and inflammatory stressors are mediated by transcription factors and molecular chaperones. The transcription factor heat shock factor 1 (HSF1) has been implicated in extending lifespan in part by increasing expression of heat shock response genes. Pyrrolidine dithiocarbamate (PDTC) is a small thiol compound that exerts in vivo and in vitro anti-inflammatory properties through mechanisms that remain unclear. Here we report that PDTC induced the release of monomeric HSF1 from the molecular chaperone heat shock protein 90 (Hsp90), with concomitant increase in HSF1 trimer formation, translocation to the nucleus, and binding to promoter of target genes in human HepG2 cells. siRNA-mediated silencing of HSF1 blocked BAG3 gene expression by PDTC. The protein levels of the co-chaperone BAG3 and its interaction partner Hsp72 were stimulated by PDTC in a dose-dependent fashion, peaking at 6h. Inhibition of Hsp90 function by geldanamycin derivatives and novobiocin elicited a pattern of HSF1 activation and BAG3 expression that was similar to PDTC. Chromatin immunoprecipitation studies showed that PDTC and the inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin enhanced the binding of HSF1 to the promoter of several target genes, including BAG3, HSPA1A, HSPA1B, FKBP4, STIP1 and UBB. Cell treatment with PDTC increased significantly the level of Hsp90α thiol oxidation, a posttranslational modification known to inhibit its chaperone function. These results unravel a previously unrecognized mechanism by which PDTC and related compounds could confer cellular protection against inflammation through HSF1-induced expression of heat shock response genes.

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Available from: Michael J Pazin, Jul 04, 2014
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    • "Several studies have shown that HSF1 regulates the BAG3 gene expression induced by a cellular stimulus [13] [15] [20] [29]. Additionally , the autoactivation of the BAG3 gene in human glial cells, but not in other non-glial cell lines has led to a suggestion for the possible role of nuclear BAG3 [30]. "
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    ABSTRACT: Bcl2-associated athoanogene (BAG) 3 is a member of the co-chaperone BAG family. It is induced by stressful stimuli such as heat shock and heavy metals, and it regulates cellular adaptive responses against stressful conditions. In this study, we identified a novel role for BAG3 in regulating the nuclear shuttling of HSF1 during heat stress. The expression level of BAG3 was induced by heat stress in HeLa cells. Interestingly, BAG3 rapidly translocalized to the nucleus upon heat stress. Immunoprecipitation assay showed that BAG3 interacts with HSF1 under normal and stressed conditions and co-translocalizes to the nucleus upon heat stress. We also demonstrated that BAG3 interacts with HSF1 via its BAG domain. Over-expression of BAG3 down-regulates the level of nuclear HSF1 by exporting it to the cytoplasm during the recovery period. Depletion of BAG3 using siRNA results in reduced nuclear HSF1 and decreased Hsp70 promoter activity. BAG3 in MEF(hsf1(-/-)) cells actively translocalizes to the nucleus upon heat stress suggesting that BAG3 plays a key role in the processing of the nucleocytoplasmic shuttling of HSF1 upon heat stress. Copyright © 2015. Published by Elsevier Inc.
    Biochemical and Biophysical Research Communications 07/2015; 12(2). DOI:10.1016/j.bbrc.2015.07.006 · 2.30 Impact Factor
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    • "Taken together the novel interaction between the AHR and two other mitochondrial associated proteins are of great interest. The first, Bag3, a prooncoprotein, is involved in the mitochondrial stress response and disease [47, 48]. It has also been shown to inhibit the apoptotic response through interactions with Bcl-2 family members [49, 50]. "
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    ABSTRACT: The aryl-hydrocarbon receptor (AHR), a ligand activated PAS superfamily transcription factor, mediates most, if not all, of the toxicity induced upon exposure to various dioxins, dibenzofurans, and planar polyhalogenated biphenyls. While AHR-mediated gene regulation plays a central role in the toxic response to dioxin exposure, a comprehensive understanding of AHR biology remains elusive. AHR-mediated signaling starts in the cytoplasm, where the receptor can be found in a complex with the heat shock protein of 90 kDa (Hsp90) and the immunophilin-like protein, aryl-hydrocarbon receptor-interacting protein (AIP). The role these chaperones and other putative interactors of the AHR play in the toxic response is not known. To more comprehensively define the AHR-protein interaction network (AHR-PIN) and identify other potential pathways involved in the toxic response, a proteomic approach was undertaken. Using tandem affinity purification (TAP) and mass spectrometry we have identified several novel protein interactions with the AHR. These interactions physically link the AHR to proteins involved in the immune and cellular stress responses, gene regulation not mediated directly via the traditional AHR:ARNT heterodimer, and mitochondrial function. This new insight into the AHR signaling network identifies possible secondary signaling pathways involved in xenobiotic-induced toxicity.
    Journal of Toxicology 12/2013; 2013(6):279829. DOI:10.1155/2013/279829
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    • "Thus it seems that NF-kB regulates PQC by either modulating autophagy induction by aggregates or aggresomes, or by modulating aggresome targeting to autophagosomes. We consequently focused on BAG3, an Hsp70 co-chaperone, whose gene transcription is activated by heat shock (through HSF1 transcription factor) (Pagliuca et al., 2003; Song et al., 2010). BAG3 was recently described to be a molecular switch that determines whether proteins are degraded in a proteasomal or autophagic manner (Gamerdinger et al., 2009) and was found to increase autophagic activity (Carra, 2009). "
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    ABSTRACT: We previously found that the NF-κB transcription factor is activated during the recovery period after heat shock; moreover, we demonstrated that NF-κB is essential for cell survival after heat shock by activating autophagy, a mechanism that probably helps the cell to cope with hyperthermic stress through clearance of damaged proteins. In this study, we analyze the involvement of NF-κB in basal and heat-stress-induced protein quality control, by comparing the level of multiubiquitylated and/or aggregated proteins, and proteasome and autophagic activity in NF-κB-competent and NF-κB-incompetent cells. We show that NF-κB has only a minor role in basal protein quality control, where it modulates autophagosome maturation. By contrast, NF-κB is shown to be a key player in protein quality control after hyperthermia. Indeed, NF-κB-incompetent cells show highly increased levels of multiubiquitylated and/or aggregated proteins and aggresome clearance defects; a phenotype that disappears when NF-κB activity is restored to normal. We demonstrate that during heat shock recovery NF-κB activates selective removal of misfolded or aggregated proteins--a process also called 'aggrephagy'--by controlling the expression of BAG3 and HSPB8 and by modulating the level of the BAG3-HspB8 complex. Thus NF-κB-mediated increase in the level of the BAG3-HspB8 complex leads to upregulation of aggrephagy and clearance of irreversibly damaged proteins and might increase cell survival in conditions of hyperthermia.
    Journal of Cell Science 02/2012; 125(Pt 5):1141-51. DOI:10.1242/jcs.091041 · 5.43 Impact Factor
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