Phosphorylation of HSF1 by MAPK-Activated Protein Kinase 2 on Serine 121, Inhibits Transcriptional Activity and Promotes HSP90 Binding

Xiaozhe Wang,Md Abdul Khaleque,Mei Juan Zhao,Rong Zhong,Matthias Gaestel,Stuart K Calderwood

doi:10.1074/jbc.m505822200

Abstract

Heat shock transcription factor 1 (HSF1) monitors the structural integrity of intracellular proteins and its regulation is essential for the health and longevity of eukaryotic organisms. HSF1 also plays a role in the acute inflammatory response in the negative regulation of cytokine gene transcription. Here we show, for the first time, that HSF1 is regulated by the proinflammatory protein kinase MAPKAP kinase 2 (MK2). We have shown that MK2 directly phosphorylates HSF1 and inhibits activity by decreasing its ability to bind the heat shock elements (HSE) found in the promoters of target genes encoding the HSP molecular chaperones and cytokine genes. We show that activation of HSF1 to bind HSE in hsp promoters is inhibited through the phosphorylation of a specific residue, serine 121 by MK2. A potential mechanism for MK2-induced HSF1 inactivation is suggested by the findings that phosphorylation of serine 121 enhances HSF1 binding to HSP90, a major repressor of HSF1. Dephosphorylation of serine 121 in cells exposed to non-steroidal anti-inflammatory drugs leads to HSP90 dissociation from HSF1, which then forms active DNA binding trimers. These experiments indicate a novel mechanism for the regulation of HSF1 by proinflammatory signaling and may permit HSF1 to respond rapidly to extracellular events, permitting optimal physiological regulation.

Highlights

Applies, and malignant transformation is associated with aberrantly high levels of HSP [8, 9]
Overexpression of HA-Heat shock transcription factor 1 (HSF1) led to the activation of heat shock promoter (HSP70B) activity and such HSF1 activation of the HSP70B promoter activity was inhibited by 50 – 60% when cells were co-transfected with pMyc-MAPKAP kinase 2 (MK2) (Fig. 1A)
We show that MK2 directly inhibits HSF1 activity through a mechanism involving phosphorylation on serine 121 and that anti-inflammatory drugs can antagonize this effect and activate HSF1 by direct inhibition of MK2 (Figs. 1 and 2)

Summary

Introduction

Applies, and malignant transformation is associated with aberrantly high levels of HSP [8, 9]. Activation is controlled by HSF1 binding to the molecular chaperone HSP90, and HSP90 binding maintains the monomeric state [13, 20] This form of regulation is found in other transcription factor families including the nuclear receptors [21]. The monomer to trimer transition can be induced by high concentrations of the non-steroidal anti-inflammatory drugs (NSAIDs) including aspirin, ibuprofen, and sodium salicylate (NaSal) [22, 23]. These compounds derive the majority of their anti-inflammatory activity through inhibition of the cyclooxygenase enzymes [24, 25]. Our experiments indicate that the protein kinase MK2 is an inhibitor of HSF1 and may exert its effects on the protein by direct phosphorylation

Methods

Results

Conclusion