Transcription of the Transforming Growth Factor β Activating Integrin β8 Subunit Is Regulated by SP3, AP-1, and the p38 Pathway

Jennifer A Markovics,Jun Araya,Stephanie Cambier,David Jablons,Arthur Hill,Paul J Wolters,Stephen L Nishimura

doi:10.1074/jbc.m110.113977

Jennifer A Markovics, Jun Araya + Show 5 more

Open Access

https://doi.org/10.1074/jbc.m110.113977

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Abstract

Integrin alphavbeta8 is a critical regulator of transforming growth factor beta activation in vasculogenesis during development, immune regulation, and endothelial/epithelial-mesenchymal homeostasis. Recent studies have suggested roles for integrin beta8 in the pathogenesis of chronic obstructive pulmonary disease, brain arteriovenous malformations, and select cancers (Araya, J., Cambier, S., Markovics, J. A., Wolters, P., Jablons, D., Hill, A., Finkbeiner, W., Jones, K., Broaddus, V. C., Sheppard, D., Barzcak, A., Xiao, Y., Erle, D. J., and Nishimura, S. L. (2007) J. Clin. Invest. 117, 3551-3562; Su, H., Kim, H., Pawlikowska, L., Kitamura, H., Shen, F., Cambier, S., Markovics, J., Lawton, M. T., Sidney, S., Bollen, A. W., Kwok, P. Y., Reichardt, L., Young, W. L., Yang, G. Y., and Nishimura, S. L. (2010) Am. J. Pathol. 176, 1018-1027; Culhane, A. C., and Quackenbush, J. (2009) Cancer Res. 69, 7480-7485; Cambier, S., Mu, D. Z., O'Connell, D., Boylen, K., Travis, W., Liu, W. H., Broaddus, V. C., and Nishimura, S. L. (2000) Cancer Res. 60, 7084-7093). Here we report the first identification and characterization of the promoter for ITGB8. We show that a SP binding site and a cyclic AMP response element (CRE) in the ITGB8 core promoter are required for its expression and that Sp1, Sp3, and several AP-1 transcription factors form a complex that binds to these sites in a p38-dependent manner. Furthermore, we demonstrate the requirement for Sp3, ATF-2, and p38 for the transcription and protein expression of integrin beta8. Additionally, reduction of SP3 or inhibition of p38 blocks alphavbeta8-mediated transforming growth factor beta activation. These results place integrin beta8 expression and activity under the control of ubiquitous transcription factors in a stress-activated and pro-inflammatory pathway.

Highlights

Characterization of the Transcriptional Start Site of ITGB8— To determine the transcriptional start site (TSS) of ITGB8, Sequence analysis indicates that no TATA box is present in 1,213 bp of the 5Ј-flanking sequence to the most
Integrin ␣v␤8-mediated TGF-␤ Activation by Lung Fibro-Antibodies against JunD and JunB showed a significant reduc- blasts Is Regulated by the p38 Pathway—Primary adult lung tion in the intensity of DNA-binding complexes in bands 3 and fibroblasts were treated with SB202190 and subjected to a
Are Regulated by Sp3, AP-1, and the p38 Pathway—Here we report the first identification and characterization of the promoter for human ITGB8, a gene that is crucial for the regulation of TGF-␤

Summary

Introduction

Required to Drive Expression—There are four putative transcription factor binding sites with high degrees of interspecies conservation within the ITGB8 core promoter, NF␬B/c-Rel, AP4, CRE, and SP (Fig. 1B). Specific Complexes Form at the CRE and SP Sites in the Core Promoter of ITGB8—EMSAs using a probe corresponding to the sequence containing the CRE, CCAAT, and SP binding sites in the ITGB8 core promoter were performed in nuclear extracts from primary adult lung fibroblasts (Fig. 4A).

Results

Conclusion