PHD2/3-dependent hydroxylation tunes cardiac response to β-adrenergic stress via phospholamban
Liang Xie, … , Gerhard Meissner, Cam Patterson
Liang Xie, … , Gerhard Meissner, Cam Patterson
Published June 15, 2015
Citation Information: J Clin Invest. 2015;125(7):2759-2771. https://doi.org/10.1172/JCI80369.
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PHD2/3-dependent hydroxylation tunes cardiac response to β-adrenergic stress via phospholamban

Abstract

Ischemic heart disease is the leading cause of heart failure. Both clinical trials and experimental animal studies demonstrate that chronic hypoxia can induce contractile dysfunction even before substantial ventricular damage, implicating a direct role of oxygen in the regulation of cardiac contractile function. Prolyl hydroxylase domain (PHD) proteins are well recognized as oxygen sensors and mediate a wide variety of cellular events by hydroxylating a growing list of protein substrates. Both PHD2 and PHD3 are highly expressed in the heart, yet their functional roles in modulating contractile function remain incompletely understood. Here, we report that combined deletion of Phd2 and Phd3 dramatically decreased expression of phospholamban (PLN), resulted in sustained activation of calcium/calmodulin-activated kinase II (CaMKII), and sensitized mice to chronic β-adrenergic stress–induced myocardial injury. We have provided evidence that thyroid hormone receptor-α (TR-α), a transcriptional regulator of PLN, interacts with PHD2 and PHD3 and is hydroxylated at 2 proline residues. Inhibition of PHDs increased the interaction between TR-α and nuclear receptor corepressor 2 (NCOR2) and suppressed Pln transcription. Together, these observations provide mechanistic insight into how oxygen directly modulates cardiac contractility and suggest that cardiac function could be modulated therapeutically by tuning PHD enzymatic activity.

Authors

Liang Xie, Xinchun Pi, W.H. Davin Townley-Tilson, Na Li, Xander H.T. Wehrens, Mark L. Entman, George E. Taffet, Ashutosh Mishra, Junmin Peng, Jonathan C. Schisler, Gerhard Meissner, Cam Patterson

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Figure 8

Hypoxia increases the interaction between TR-α and NCOR2.

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Hypoxia increases the interaction between TR-α and NCOR2. (A) Replacemen...
(A) Replacement of the P160 residue of TR-α alters NCOR2-binding affinity. Molecular structures of proline, 4-hydroxy-proline, valine, and serine are shown. HEK293 cells were transfected with TR-α, TR-αP160S, or TR-αP160V, together with pcDNA3 or NCOR2, as indicated, followed by IP with NCOR2. Western blot analyses were then performed with the indicated antibodies. (B and C) Hypoxia potentiates the interaction between NCOR2 and TR-α. HEK293 cells cultured under 21% O2 conditions were transfected with constructs expressing TR-α or TR-β, together with pcDNA3 or NCOR2, as indicated, and were cultured under 21% or 1% O2 conditions for 8 hours. Flag-NCOR2 was IP, and Western blotting was performed with the indicated antibodies. Densitometric analysis of the IP TR-α is shown in C. n = 3, *P < 0.01, 2-tailed Student’s t test. (D) Schematic illustrating that PLN downregulation in the heart by hypoxia or PHD2 and PHD3 depletion contributes to myocardial injury induced by chronic β-AR stress. PHD2- and PHD3-mediated hydroxylation of TR-α blocks recruitment of the transcriptional repressor NCOR2 to the promoter region of Pln, resulting in transcription of Pln. Inhibition of TR-α hydroxylation, either through PHD2 and PHD3 depletion or through hypoxia, leads to increased recruitment of NCOR2 and suppression of Pln transcription. This decrease in PLN expression exacerbates cardiomyocyte apoptosis, cardiac hypertrophy, and arrhythmia induced by chronic β-AR stress.