Mitofusin 2 Is Required for the Maturation of Embryonic Stem Cell-Derived Cardiomyocytes via a GRP75-Dependent Suppression of the ROS/PI3K/AKT/mTOR Axis
Restricted accessResearch articleFirst published online June, 2026
Mitofusin 2 Is Required for the Maturation of Embryonic Stem Cell-Derived Cardiomyocytes via a GRP75-Dependent Suppression of the ROS/PI3K/AKT/mTOR Axis
Pluripotent stem cell-derived cardiomyocytes (PSC-CMs) have the potential for use in cell-based therapy, disease modeling, and drug toxicity testing. However, under the conventional differentiation protocol, PSC-CMs are immature and differ from adult cardiomyocytes in electrophysiological characteristics, calcium kinetics, cellular morphology, metabolism, and gene expression. MFN2 tethers sarcoplasmic reticulum (SR) and mitochondria and mediates their interaction via mitochondria-associated endoplasmic reticulum membranes, which tunes the cytosolic Ca2+ and reactive oxygen species (ROS) signaling. We aim to investigate if MFN2 would regulate murine embryonic stem cell-derived cardiomyocyte (mESC-CM) maturation, and if yes, what are the underlying mechanisms.
Results:
MFN2 knockdown caused detrimental effects on mESC-CM maturation in terms of structure, cytosolic calcium kinetics, electrophysiology, and metabolism. Mechanistically, MFN2 knockdown increased proliferative capacity, increased ROS and activated PI3K/AKT/mTOR activity, and these were all reversed by the ROS scavenger N-acetylcysteine. Meanwhile, MFN2 knockdown decreased the IP3R-VDAC coupling mediated by GRP75. Importantly, GRP75 overexpression restored the decreased IP3R-VDAC coupling, reversed the increased cellular ROS, and reversed the increased PI3K/AKT/mTOR activity caused by MFN2 knockdown. Rapamycin, an mTOR inhibitor, reduced the increased proliferative capacity and restored the impaired electrophysiology caused by MFN2 knockdown.
Innovation:
The current study is the first study to reveal that MFN2-mediated SR-mitochondrial interaction is required for the mESC-CM maturation through the ROS/PI3K/AKT/mTOR axis.
Conclusion:
MFN2 is required for the maturation of mESC-CMs through GRP75-dependent, mTOR-mediated suppression of proliferative capacity via the ROS/PI3K/AKT pathway. Our findings advance the understanding of PSC-CM maturation and provide novel insight for strategies to promote PSC-CM maturation. Antioxid. Redox Signal. 44, 799–821.
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