Submitted on April 30, 2007
Accepted on June 24, 2007
The CREB leucine zipper regulates CREB phosphorylation, cardiomyopathy, and lethality in a transgenic model of heart failure
Gordon Spencer Huggins1*, John J Lepore2, Sarah Greytak1, Richard D. Patten3, Rachel McNamee4, Mark J. Aronovitz1, Paul Wang5, and Guy L. Reed4
1 Molecular Cardiology Research Institute, Tufts-New England Medical Center, Boston, Massachusetts, United States
2 GlaxoSMithKline, Philadelphia, Pennsylvania, United States
3 Molecular Cardiology Research Institute-Tufts-New England Medical Center, Boston, Massachusetts, United States
4 Department of Medicine, Medical College of Georgia, Augusta, Georgia, United States
5 Department of Medicine, Stanford University Medical Center, Stanford, California, United States
* To whom correspondence should be addressed. E-mail: ghuggins{at}tufts-nemc.org.
Signaling through cyclic AMP plays an important role in heart failure. Phosphorylation of cyclic-AMP response element binding protein (CREB) at serine-133 regulates gene expression in the heart. We examined the functional significance of CREB-S133 phosphorylation by comparing transgenic models in which a phosphorylation resistant CREB-S133A mutant containing either an intact or a mutated leucine zipper domain (CREB-S133A-LZ) was expressed in the heart. In vitro, CREB-S133A retained the ability to interact with wild type CREB, whereas CREB-S133A-LZ did not. In vivo, CREB-S133A and CREB-S133A-LZ were expressed at comparable levels in the heart; however CREB-S133A markedly suppressed the phosphorylation of endogenous CREB, while CREB-S133A-LZ had no effect. The one-year survival of mice from two CREB-S133A-LZ transgenic (Tg) lines was equivalent to non-transgenic littermate control mice (NTg), whereas Tg CREB-S133A mice died with heart failure at a median 30 weeks of age (p<0.0001). CREB-S133A mice had altered gene expression characteristic of the failing heart, whereas CREB-S133A-LZ mice did not. Left ventricular contractile function was substantially reduced in CREB-S133A mice versus NTg mice and only modestly reduced in CREB-S133A-LZ mice (p<0.02). When considered in light of other studies these findings indicate that overexpression of the CREB leucine zipper is required both for inhibition of endogenous CREB phosphorylation and for cardiomyopathy in this murine model of heart failure.
