Calcineurin Activates Cytoglobin Transcription in Hypoxic Myocytes

doi:10.1074/jbc.M809572200

Calcineurin Activates Cytoglobin Transcription in Hypoxic Myocytes*

Departments of ^‡Internal Medicine and ^¶Molecular Biology and the ^∥Donald W. Reynolds Cardiovascular Clinical Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390 and the ^§Cell and Cancer Biology Branch, NCI, National Institutes of Health, Bethesda, Maryland 20892

3 To whom correspondence should be addressed: Dept. of Internal Medicine, University of Texas Southwestern Medical Ctr., 5323 Harry Hines Blvd., Dallas, TX 75390-8573. E-mail: pradeep.mammen{at}utsouthwestern.edu.

Abstract

Cardiac hypertrophy develops in response to a variety of cardiovascular stresses and results in activation of numerous signaling cascades and proteins. In the present study, we demonstrate that cytoglobin is a stress-responsive hemoprotein in the hypoxia-induced hypertrophic myocardium and it is transcriptionally regulated by calcineurin-dependent transcription factors. The cytoglobin transcript level is abundantly expressed in the adult heart and in response to hypoxia cytoglobin expression is markedly up-regulated within the hypoxia-induced hypertrophic heart. To define the molecular mechanism resulting in the induction of cytoglobin, we undertook a transcriptional analysis of the 5′ upstream regulatory region of the cytoglobin gene. Evolutionarily conserved binding elements for transcription factors HIF-1, AP-1, and NFAT are located within the upstream region of the cytoglobin gene. Transcriptional assays demonstrated that calcineurin activity modulates cytoglobin transcription. Increased calcineurin activity enhances the ability of NFAT and AP-1 to bind to the putative cytoglobin promoter, especially under hypoxic conditions. In addition, inhibition of calcineurin, NFAT, and/or AP-1 activities decreases endogenous cytoglobin transcript and protein levels. Thus, the regulation of cytoglobin transcription by calcineurin-dependent transcription factors suggests that cytoglobin may have a functional role in calcium-dependent events accompanying cardiac remodeling.

Footnotes

↵4 The abbreviations used are: Cygb, cytoglobin; Mb, myoglobin; NFAT, nuclear factor of activated T cell; AP-1, activator protein; HIF-1, hypoxia-inducible factor-1; RT, reverse transcription; qRT, quantitative reverse transcription; RIB, ribosome; ARE, AP-1-responsive element; NRE, NFAT-responsive element; CMV, cytomegalovirus; CsA, cyclosporin A; GFP, green fluorescent protein; EMSA, electrophoretic mobility shift assay; WT, wild type; ChIP, chromatin immunoprecipitation; dn, dominant negative.
↵* This study was supported, in whole or in part, by National Institutes of Health Grants HL-63788 (to D. J. G.) and HL-076440 (to P. P. A. M.). This study was also supported by grants from the American Heart Association-Texas Affiliate to (P. P. A. M.), the Donald W. Reynolds Clinical Cardiovascular Research Center (to D. J. G. and P. P. A. M.), and the GlaxoSmithKline Research Foundation (to P. P. A. M.).
↵1 These authors contributed equally to this manuscript.
↵2 Current address: Lillehei Heart Inst., University of Minnesota, Minneapolis, MN 55455.
- Received December 19, 2008.
- Revision received January 30, 2009.
The American Society for Biochemistry and Molecular Biology, Inc.