Reduced Ets Domain-containing Protein Elk1 Promotes Pulmonary Fibrosis via Increased Integrin αvβ6 Expression

Amanda L Tatler,Anthony Habgood,Joanne Porte,Alison E John,Anastasios Stavrou,Emily Hodge,Cheryl Kerama-Likoko,Shelia M Violette,Paul H Weinreb,Alan J Knox,Geoffrey Laurent,Helen Parfrey,Paul John Wolters,William Wallace,Siegfried Alberti,Alfred Nordheim,Gisli Jenkins

doi:10.1074/jbc.m115.692368

Abstract

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with high mortality. Active TGFβ1 is considered central to the pathogenesis of IPF. A major mechanism of TGFβ1 activation in the lung involves the epithelially restricted αvβ6 integrin. Expression of the αvβ6 integrin is dramatically increased in IPF. How αvβ6 integrin expression is regulated in the pulmonary epithelium is unknown. Here we identify a region in the β6 subunit gene (ITGB6) promoter acting to markedly repress basal gene transcription, which responds to both the Ets domain-containing protein Elk1 (Elk1) and the glucocorticoid receptor (GR). Both Elk1 and GR can regulate αvβ6 integrin expression in vitro. We demonstrate Elk1 binding to the ITGB6 promoter basally and that manipulation of Elk1 or Elk1 binding alters ITGB6 promoter activity, gene transcription, and αvβ6 integrin expression. Crucially, we find that loss of Elk1 causes enhanced Itgb6 expression and exaggerated lung fibrosis in an in vivo model of fibrosis, whereas the GR agonist dexamethasone inhibits Itgb6 expression. Moreover, Elk1 dysregulation is present in epithelium from patients with IPF. These data reveal a novel role for Elk1 regulating ITGB6 expression and highlight how dysregulation of Elk1 can contribute to human disease.

Highlights

From the ‡Division of Respiratory Medicine, University of Nottingham, Nottingham University Hospitals, City Campus, Nottingham NG5 1PB, United Kingdom, §Biogen Inc., Cambridge, Massachusetts 02142, the ¶Centre for Respiratory Research, University College London, London WC1E 6JF, United Kingdom, the ʈCentre for Cell Therapy and Regenerative Medicine, University of Western
We demonstrate Elk1 binding to the ITGB6 promoter basally and that manipulation of Elk1 or Elk1 binding alters ITGB6 promoter activity, gene transcription, and ␣v␤6 integrin expression
Supporting a role for Elk1 being responsible for negative regulation of ␣v␤6 integrins and confirming that Elk1 protein expression is aberrant in fibrosis, we found that NF donors had high levels of epithelial Elk1 protein expression, whereas PF donors had minimal expression of Elk1 within the lung epithelium (Fig. 6F, iii and iv)

Summary

Introduction

From the ‡Division of Respiratory Medicine, University of Nottingham, Nottingham University Hospitals, City Campus, Nottingham NG5 1PB, United Kingdom, §Biogen Inc., Cambridge, Massachusetts 02142, the ¶Centre for Respiratory Research, University College London, London WC1E 6JF, United Kingdom, the ʈCentre for Cell Therapy and Regenerative Medicine, University of Western. We identify a region in the ␤6 subunit gene (ITGB6) promoter acting to markedly repress basal gene transcription, which responds to both the Ets domain-containing protein Elk (Elk1) and the glucocorticoid receptor (GR) Both Elk and GR can regulate ␣v␤6 integrin expression in vitro. Elk dysregulation is present in epithelium from patients with IPF These data reveal a novel role for Elk regulating ITGB6 expression and highlight how dysregulation of Elk can contribute to human disease. Tel.: 44-1158231106; E-mail: amanda.tatler@ nottingham.ac.uk. 2 The abbreviations used are: IPF, idiopathic pulmonary fibrosis; GR, glucocorticoid receptor; iHBEC, immortalized human bronchial epithelial cell; SAEC, small airway epithelial cell; QPCR, quantitative PCR; SDM, site-directed mutagenesis; PF, pulmonary fibrosis; NF, non-fibrotic; MFI, mean fluorescence intensity

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