Background: Mitochondrial ATP synthase (Complex V) deficiency is frequently associated with severe cardiomyopathy, yet how impaired ATP synthase activity disrupts cardiac differentiation and metabolic maturation remains unclear. TMEM70 mutations represent one of the most common nuclear-encoded Complex V deficiencies with a high incidence in cardiac disease. Unfortunately, because of the lack of animal models, the incidence of TMEM70 deficiency in cardiogenesis and maturation has remained unexplored. Herein, by integrating iPSC‑derived cardiomyocytes with drug‑screening approaches, we propose AMPK as a potential pathophysiological target because of its incidence in restoring mitochondrial performance, cardiac remodeling, and elevated beat frequency observed in TMEM70-deficient cardiomyocytes.
Objective: Investigating the impact of AMPK activation on cardiomyocyte performance under TMEM70‑dependent Complex V deficiency.
Materials and Methods: We generated TMEM70 related Complex V deficient cell lines (TMEM70WT/WT, TMEM70KO/KO and TMEM70SNP/SNP) using CRISPR-engineered human iPSCs differentiated into cardiomyocytes from a healthy donor. After cardiomyocyte differentiation, treatments with MK‑8722 (a pan-AMPK activator) were applied, followed by a series of physiological and biochemical assessments.
Main results: TMEM70-deficient cardiomyocytes display a detrimental Complex V assembly, a lower mitochondrial membrane potential and respiration (N=18), as well as aberrant cristae distribution. Simultaneously, we observed that TMEM70-deficient cardiomyocytes displayed a substantial increase in protein levels associated with hypertrophic cardiomyopathy and a diminished mitochondrial respiratory proteome compared to WT cardiomyocytes (N=5). These changes were reflected in poor contractile capacity and elevated beat frequency (N=8) impaired respiratory capacity and features of pathological remodeling, indicating a failure to adapt to the metabolic demands associated to maturation. To restore cardiomyocyte function, we treated TMEM70‑deficient cardiomyocytes with MK‑8722 for 30 days. Chronic AMPK activation enhanced mitochondrial membrane potential and respiration, accompanied by an increase in oxidative phosphorylation (OXPHOS) proteins (N=12). Finally, AMPK activation reduced beat frequency and enhanced contractile capacity of TMEM70-deficient cardiomyocytes. Proteomic and metabolomic analyses reveal that AMPK activation induces a coordinated remodeling program characterized by upregulation of mitochondrial OXPHOS and tricarboxylic acid (TCA) cycle. In parallel, proteins associated with extracellular matrix organization, focal adhesion, and stress-associated contractile remodeling are markedly downregulated. Functional improvement is accompanied by normalization of spontaneous beating, reduction in calcium-dependend mediator handling (specifically P-RyR2Ser2814 and P-PLNThr17) and contractile kinetics.
Perspective: Together, these findings demonstrate that AMPK activation reprograms TMEM70-deficient cardiomyocytes by reinforcing mitochondrial metabolic capacity while suppressing pathological structural remodeling, revealing a state-dependent mechanism for functional rescue in mitochondrial cardiomyopathy. This supports the therapeutic potential of direct AMPK agonists as a disease-modifying strategy for TMEM70-related Complex V deficiency.
