Fibronectin is a stress responsive gene regulated by HSF1 in response to geldanamycin

Karim Colin Hassan Dhanani,William John Samson,Adrienne Lesley Edkins

doi:10.1038/s41598-017-18061-y

Karim Colin Hassan Dhanani, William John Samson + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-18061-y

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Journal: Scientific Reports	Publication Date: Dec 1, 2017
Citations: 16	License type: open-access

Affiliation: Rhodes University

Abstract

Fibronectin is an extracellular matrix glycoprotein with key roles in cell adhesion and migration. Hsp90 binds directly to fibronectin and Hsp90 depletion regulates fibronectin matrix stability. Where inhibition of Hsp90 with a C-terminal inhibitor, novobiocin, reduced the fibronectin matrix, treatment with an N-terminal inhibitor, geldanamycin, increased fibronectin levels. Geldanamycin treatment induced a stress response and a strong dose and time dependent increase in fibronectin mRNA via activation of the fibronectin promoter. Three putative heat shock elements (HSEs) were identified in the fibronectin promoter. Loss of two of these HSEs reduced both basal and geldanamycin-induced promoter activity, as did inhibition of the stress-responsive transcription factor HSF1. Binding of HSF1 to one of the putative HSE was confirmed by ChIP under basal conditions, and occupancy shown to increase with geldanamycin treatment. These data support the hypothesis that fibronectin is stress-responsive and a functional HSF1 target gene. COLA42 and LAMB3 mRNA levels were also increased with geldanamycin indicating that regulation of extracellular matrix (ECM) genes by HSF1 may be a wider phenomenon. Taken together, these data have implications for our understanding of ECM dynamics in stress-related diseases in which HSF1 is activated, and where the clinical application of N-terminal Hsp90 inhibitors is intended.

Highlights

Tissue integrity is maintained by the attachment of cells to a network of secreted proteins, proteoglycans, glycoproteins and polysaccharides known as the extracellular matrix (ECM)
GA, along with a other N-terminal inhibitors of Hsp[90], results in the activation of the stress response[37]. This stress response is a coordinated series of molecular events that culminates in the changes in expression of stress-responsive genes through the activation of the transcription factor heat shock factor 1 (HSF1)[38]
GA but not NOV caused an accumulation of HSF1 in the nucleus of Hs578T cells (Fig. 4C). These results demonstrate that GA resulted in an activation of the HSF1 mediated stress response in our treated cells, which may explain the increases in FN promoter activity and mRNA

Summary

Introduction

Tissue integrity is maintained by the attachment of cells to a network of secreted proteins, proteoglycans, glycoproteins and polysaccharides known as the extracellular matrix (ECM). Hsp[90] is a molecular chaperone that stabilises intermediate conformations of a large number of important cellular proteins, known as client proteins[30,31] Decreased levels of both total and extracellular FN matrix were observed upon treatment of cells with the C-terminal Hsp[90] inhibitor, novobiocin (NOV), and upon depletion of Hsp[90] by RNA interference. Hsp[90] knock-down and NOV treatment reduced the FN matrix, while GA treatment appeared to cause an increase in the levels of the FN ECM. GA, along with a other N-terminal inhibitors of Hsp[90], results in the activation of the stress response[37] This stress response is a coordinated series of molecular events that culminates in the changes in expression of stress-responsive genes through the activation of the transcription factor heat shock factor 1 (HSF1)[38]. Based on our observations of increased FN in response to GA treatment, and the fact that GA is known to induce a stress response, we investigated whether FN1 was a stress responsive gene

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Conclusion