Key result
Cardiomyocyte Fundc1 deletion impairs cardiac function via disrupted mitochondrial calcium and aberrant fission.
Why the study?
Does FUNDC1 modulate mitochondria-associated endoplasmic reticulum membranes and maintain cardiac function in vivo?
Does FUNDC1 modulate mitochondria-associated endoplasmic reticulum membranes and maintain cardiac function in vivo?
Identifying the FUNDC1/IP3R2/CREB/Fis1 axis reveals a novel molecular mechanism linking disrupted mitochondria-associated endoplasmic reticulum membranes to the pathogenesis of heart failure.
Background: FUN14 domain containing 1 (FUNDC1) is a highly conserved outer mitochondrial membrane protein. The aim of this study is to examine whether FUNDC1 modulates the mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs), mitochondrial morphology, and function in cardiomyocytes and intact hearts. Methods: The impacts of FUNDC1 on MAMs formation and cardiac functions were studied in mouse neonatal cardiomyocytes, in mice with cardiomyocyte-specific Fundc1 gene knockout ( Fundc1 f/Y /Cre αMyHC+/− ), and in the cardiac tissues of the patients with heart failure. Results: In mouse neonatal cardiomyocytes and intact hearts, FUNDC1 was localized in MAMs by binding to ER-resided inositol 1,4,5-trisphosphate type 2 receptor (IP 3 R2). Fundc1 ablation disrupted MAMs and reduced the levels of IP 3 R2 and Ca 2+ in both mitochondria and cytosol, whereas overexpression of Fundc1 increased the levels of IP 3 R2 and Ca 2+ in both mitochondria and cytosol. Consistently, Fundc1 ablation increased Ca 2+ levels in ER, whereas Fundc1 overexpression lowered ER Ca 2+ levels. Further, Fundc1 ablation in cardiomyocytes elongated mitochondria and compromised mitochondrial functions. Mechanistically, we found that Fundc1 ablation-induced reduction of intracellular Ca 2+ levels suppressed mitochondrial fission 1 protein ( Fis1 ) expression and mitochondrial fission by reducing the binding of the cAMP response element binding protein (CREB) in the Fis1 promoter. Fundc1 f/Y /Cre αMyHC+/− mice but not their littermate control mice ( Fundc1 wt/Y /Cre αMyHC+/− ) exhibited cardiac dysfunction. The ligation of the left ventricle artery of Fundc1 f/Y /Cre αMyHC+/− mice caused more severe cardiac dysfunction than those in sham-treated Fundc1 f/Y /Cre αMyHC+/− mice. Finally, we found that the FUNDC1/MAMs/CREB/Fis1 signaling axis was significantly suppressed in patients with heart failure. Conclusions: We conclude that FUNDC1 binds to IP 3 R2 to modulate ER Ca 2+ release into mitochondria and cytosol. Further, a disruption of the FUNDC1 and IP 3 R2 interaction lowers the levels of Ca 2+ in mitochondria and cytosol, both of which instigate aberrant mitochondrial fission, mitochondrial dysfunction, cardiac dysfunction, and heart failure.
No takes yet. Share an insight, caveat, or question.
Wu et al. (2017) studied Heart Failure / Cardiac Dysfunction. Fundc1 gene knockout or overexpression vs. Wild-type littermates or control donors was evaluated on Cardiac function, mitochondrial morphology, and intracellular calcium levels. Cardiomyocyte-specific deletion of Fundc1 disrupted mitochondria-associated endoplasmic reticulum membranes and reduced mitochondrial calcium levels, causing aberrant mitochondrial fission and cardiac dysfunction.