Compound A, a Selective Glucocorticoid Receptor Modulator, Enhances Heat Shock Protein Hsp70 Gene Promoter Activation

Abstract

Compound A possesses glucocorticoid receptor (GR)-dependent anti-inflammatory properties. Just like classical GR ligands, Compound A can repress NF-κB-mediated gene expression. However, the monomeric Compound A-activated GR is unable to trigger glucocorticoid response element-regulated gene expression. The heat shock response potently activates heat shock factor 1 (HSF1), upregulates Hsp70, a known GR chaperone, and also modulates various aspects of inflammation. We found that the selective GR modulator Compound A and heat shock trigger similar cellular effects in A549 lung epithelial cells. With regard to their anti-inflammatory mechanism, heat shock and Compound A are both able to reduce TNF-stimulated IκBα degradation and NF-κB p65 nuclear translocation. We established an interaction between Compound A-activated GR and Hsp70, but remarkably, although the presence of the Hsp70 chaperone as such appears pivotal for the Compound A-mediated inflammatory gene repression, subsequent novel Hsp70 protein synthesis is uncoupled from an observed CpdA-induced Hsp70 mRNA upregulation and hence obsolete in mediating CpdA’s anti-inflammatory effect. The lack of a Compound A-induced increase in Hsp70 protein levels in A549 cells is not mediated by a rapid proteasomal degradation of Hsp70 or by a Compound A-induced general block on translation. Similar to heat shock, Compound A can upregulate transcription of Hsp70 genes in various cell lines and BALB/c mice. Interestingly, whereas Compound A-dependent Hsp70 promoter activation is GR-dependent but HSF1-independent, heat shock-induced Hsp70 expression alternatively occurs in a GR-independent and HSF1-dependent manner in A549 lung epithelial cells.

Chromatin recruitment of activated AMPK drives fasting response genes co-controlled by GR and PPARα

“…The pXP2d2-rPAPI-luciferase reporter vector (28), the plasmids encoding the full size GR bait (pCLG-GR; (29) and the irrelevant bait containing a fusion with E. coli DHFR (pCLG-eDHFR; (30)) and the empty control prey plasmid encoding unfused gp130 (pMG1) have been described previously (27). The PRKAG2 and PRKAG3 prey plasmids (pMG1-PRKAG2 and pMG1-PRKAG3, respectively) were generated by Gateway (Thermo Fisher Scientific) recombinatorial cloning of the full size PRKAG2 and PRKAG3 entry clones from the human ORFeome version 8.1 collection (31) into the pMG1 vector as described (27).…”

Selective glucocorticoid receptor modulation: New directions with non-steroidal scaffolds

“…Heat shock induces HSP70 expression in a heat shock factor protein 1 (HSF1)-dependent and GR-independent manner, whereas CpdA induces the expression in a HSF1-independent and GR-dependent manner. Even more intriguing is the fact that following CpdA a clear HSP70 gene expression activation is observed in absence of a concomitant rise in (additional) HSP70 protein, in L929sA and A549 cell lines (Beck et al, 2013). Although the SEGRMs CpdA and ZK 216346 have shown to be able to translocate GR into the nucleus, the extent of their impact on GR's nuclear accumulation is less pronounced than achieved with classic GCs and appears to differ depending on the cell type (De Bosscher et al, 2005;Dewint et al, 2008;Yemelyanov et al, 2008;Robertson et al, 2010;Reuter et al, 2012b;Presman et al, 2014;Drebert et al, 2015).…”

“…indicates positive regulation, indicates negative regulation. assumption that an anti-inflammatory therapy with less side effects remains a feasible goal (De Bosscher et al, 2005, 2010a, 2014Zhang et al, 2009b;Reber et al, 2012;Thiele et al, 2012;Beck et al, 2013;Rauner et al, 2013;Saksida et al, 2014). However, CpdA's lability (Wust et al, 2009), in combination with a narrow therapeutic range, causes this SEGRM to be inappropriate for therapy, yet excellent as a tool compound for research purposes.…”

Targeting glucocorticoid side effects: selective glucocorticoid receptor modulator or glucocorticoid‐induced leucine zipper? A perspective

“…Compound A (CpdA) has been described as the most “dissociated” SGRM, because it does not induce GR dimerization or transcriptional activation, but exerts selective transrepressive effects on the NF‐κB pathway. CpdA is able to enhance specific GR‐dependent expression in certain cases (56, 57). These are not classic GRE‐based transactivation events.…”