Abstract
The objective of this study was to identify unknown modulators of Calcineurin (Cn)-NFAT signaling. Measurement of NFAT reporter driven luciferase activity was therefore utilized to screen a human cardiac cDNA-library (~107 primary clones) in C2C12 cells through serial dilutions until single clones could be identified. This extensive screening strategy culminated in the identification of SUMO2 as a most efficient Cn-NFAT activator. SUMO2-mediated activation of Cn-NFAT signaling in cardiomyocytes translated into a hypertrophic phenotype. Prohypertrophic effects were also observed in mice expressing SUMO2 in the heart using AAV9 (Adeno-associated virus), complementing the in vitro findings. In addition, increased SUMO2-mediated sumoylation in human cardiomyopathy patients and in mouse models of cardiomyopathy were observed. To decipher the underlying mechanism, we generated a sumoylation-deficient SUMO2 mutant (ΔGG). Surprisingly, ΔGG replicated Cn-NFAT-activation and the prohypertrophic effects of native SUMO2, both in vitro and in vivo, suggesting a sumoylation-independent mechanism. Finally, we discerned a direct interaction between SUMO2 and CnA, which promotes CnA nuclear localization. In conclusion, we identified SUMO2 as a novel activator of Cn-NFAT signaling in cardiomyocytes. In broader terms, these findings reveal an unexpected role for SUMO2 in cardiac hypertrophy and cardiomyopathy, which may open the possibility for therapeutic manipulation of this pathway.
Highlights
The heart reacts to any pathological biomechanical stress typically by developing myocardial hypertrophy
Cn-NFAT signaling is one of the crucial cardiac signaling pathways causing the development of pathological hypertrophy upon increased biomechanical stress, e.g., remodeling following myocardial infarction, chronic hypertension or valvular heart disease[34,35,36]
Though extensive knowledge has been accumulated over the last 15 years about the role calcineurin plays in the heart, there are still very few direct calcineurin activators known to date, besides the upstream calcium-calmodulin-axis
Summary
The heart reacts to any pathological biomechanical stress typically by developing myocardial hypertrophy. Activation of the Cn-NFAT pathway in transgenic mice overexpressing a constitutively active mutant of Cn causes dramatic cardiac hypertrophy with severe fibrosis and activation of the molecular hypertrophic program[2]. Cardiomyocytes from these mice hearts are disorganized and hypertrophic with doubled cross-sectional area compared to wild type cardiomyocytes. To the inhibition of pathological cardiac hypertrophy in response to pressure overload or stimulation with neuroendocrine agonist infusion[2,7,8] Together, these findings demonstrate a critical and indispensable role Cn-NFAT signaling plays in the pathological remodeling of the heart. We found strong evidence for SUMO2 activating calcineurin and cardiomyocyte hypertrophy via a sumoylation-independent mechanism, uncovering a novel pathway in the regulation of calcineurin/NFAT activity
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
