The mRNA levels of heat shock factor 1 are regulated by thermogenic signals via the cAMP-dependent transcription factor ATF3

Abstract

Heat shock factor 1 (HSF1) regulates cellular adaptation to challenges such as heat shock and oxidative and proteotoxic stresses. We have recently reported a previously unappreciated role for HSF1 in the regulation of energy metabolism in fat tissues; however, whether HSF1 is differentially expressed in adipose depots and how its levels are regulated in fat tissues remain unclear. Here, we show that HSF1 levels are higher in brown and subcutaneous fat tissues than in those in the visceral depot and that HSF1 is more abundant in differentiated, thermogenic adipocytes. Gene expression experiments indicated that HSF1 is transcriptionally regulated in fat by agents that modulate cAMP levels, by cold exposure, and by pharmacological stimulation of β-adrenergic signaling. An in silico promoter analysis helped identify a putative response element for activating transcription factor 3 (ATF3) at −258 to −250 base pairs from the HSF1 transcriptional start site, and electrophoretic mobility shift and ChIP assays confirmed ATF3 binding to this sequence. Furthermore, functional assays disclosed that ATF3 is necessary and sufficient for HSF1 regulation. Detailed gene expression analysis revealed that ATF3 is one of the most highly induced ATFs in thermogenic tissues of mice exposed to cold temperatures or treated with the β-adrenergic receptor agonist CL316,243 and that its expression is induced by modulators of cAMP levels in isolated adipocytes. To the best of our knowledge, our results show for the first time that HSF1 is transcriptionally controlled by ATF3 in response to classic stimuli that promote heat generation in thermogenic tissues.

ReporterSeq reveals genome-wide dynamic modulators of the heat shock response across diverse stressors

“…The highest scoring GO category was negative regulation of Ras signal transduction, indicating that high Ras activity leads to high HSR activity. This is consistent with a previous study showing an inverse correlation between the HSR and the Ras/PKA-inhibited Msn2/4 pathway ( Brandman et al, 2012 ) and studies concluding that the PKA activity induces the HSR ( Murshid et al, 2010 ; Verma et al, 2020 ) The lowest scoring categories included mitochondria and translation, consistent with results of a previous HSR screen ( Brandman et al, 2012 ). Knockdowns of genes involved in vacuolar acidification, a process important for many cellular activities such as protein sorting and pH maintenance ( Yamashiro et al, 1990 ) as well as regulation of the HSR ( Triandafillou et al, 2018 ) also caused a significant downregulation of the HSR.…”

PPARγ agonists delay age‐associated metabolic disease and extend longevity

“…Total RNA was extracted with TRIzol (Invitrogen), according to procedures described previously (Verma et al, 2020), from iWAT, eWAT, and BAT, liver, brain, and muscle tissues of 17‐month‐old mice, after three months of treatment with either a control diet or a diet containing Rosi. RNA was reverse transcribed into cDNA (First Strand cDNA Synthesis Kit, Roche), according to the manufacturers’ instructions.…”

“…Total RNA was extracted with TRIzol (Invitrogen), according to procedures described previously (Verma et al, 2020), from iWAT,…”

“…Total RNA was extracted with TRIzol (Invitrogen), according to procedures described previously (Verma et al, 2020), from iWAT, eWAT, and BAT, liver, brain, and muscle tissues of 17-monthold mice, after three months of treatment with either a con-…”

The forkhead box transcription factor FoxP4 regulates thermogenic programs in adipocytes

“…We have previously shown that HSF1 is induced by cold exposure and agents that increase cAMP levels ( 31 ). Furthermore, our studies have demonstrated that HSF1 plays a key role in the regulation of thermogenic tissues via induction of the expression of the metabolic coactivator PGC1α.…”