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.
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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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    • "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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