Article: Stress‐Induced Cyclin C Translocation Regulates Cardiac Mitochondrial Dynamics

Authors: Jessica M. Ponce, Grace Coen, Kathryn M. Spitler, Nikola Dragisic, Ines Martins, Antentor HintonJr, Margaret Mungai, Satya Murthy Tadinada, Hao Zhang, Gavin Y. Oudit, Long‐Sheng Song, Na Li, Peter Sicinski, Stefan Strack, E. Dale Abel, Colleen Mitchell, Duane D. Hall, and Chad E. Grueter

Journal: Journal of the American Heart Association. 2020;9:e014366

Abstract:
Background: Nuclear‐to‐mitochondrial communication regulating gene expression and mitochondrial function is a critical process following cardiac ischemic injury. In this study, we determined that cyclin C, a component of the Mediator complex, regulates cardiac and mitochondrial function in part by modifying mitochondrial fission. We tested the hypothesis that cyclin C functions as a transcriptional cofactor in the nucleus and a signaling molecule stimulating mitochondrial fission in response to stimuli such as cardiac ischemia.

Methods and Results: We utilized gain‐ and loss‐of‐function mouse models in which the CCNC (cyclin C) gene was constitutively expressed (transgenic, CycC cTg) or deleted (knockout, CycC cKO) in cardiomyocytes. The knockout and transgenic mice exhibited decreased cardiac function and altered mitochondria morphology. The hearts of knockout mice had enlarged mitochondria with increased length and area, whereas mitochondria from the hearts of transgenic mice were significantly smaller, demonstrating a role for cyclin C in regulating mitochondrial dynamics in vivo. Hearts from knockout mice displayed altered gene transcription and metabolic function, suggesting that cyclin C is essential for maintaining normal cardiac function. In vitro and in vivo studies revealed that cyclin C translocates to the cytoplasm, enhancing mitochondria fission following stress. We demonstrated that cyclin C interacts with Cdk1 (cyclin‐dependent kinase 1) in vivo following ischemia/reperfusion injury and that, consequently, pretreatment with a Cdk1 inhibitor results in reduced mitochondrial fission. This finding suggests a potential therapeutic target to regulate mitochondrial dynamics in response to stress.

Conclusions: Our study revealed that cyclin C acts as a nuclear‐to‐mitochondrial signaling factor that regulates both cardiac hypertrophic gene expression and mitochondrial fission. This finding provides new insights into the regulation of cardiac energy metabolism following acute ischemic injury.

Link to journal online: https://www.ahajournals.org/doi/10.1161/JAHA.119.014366