TMEM70 variants represent the most common nuclear cause of mitochondrial ATP synthase (Complex V) deficiency and are associated with particularly severe cardiac manifestations. Yet, how TMEM70 deficiency disrupts cardiomyocyte metabolic maturation and function remains poorly understood, in part because suitable human disease models are lacking. Here, we model TMEM70-related Complex V deficiency using CRISPR-engineered human induced pluripotent stem cells differentiated into cardiomyocytes. While TMEM70-deficient pluripotent cells retain mitochondrial function, differentiated cardiomyocytes develop reduced mitochondrial membrane potential, impaired respiratory capacity, and pathological remodeling, revealing a differentiation-dependent failure of metabolic maturation. Chronic activation of AMP-activated protein kinase (AMPK) restores mitochondrial respiratory capacity despite persistent Complex V deficiency. Proteomic and metabolomic analyses reveal that AMPK activation in TMEM70-deficient cardiomyocytes reinforces mitochondrial and fatty-acid metabolism while suppressing pathological structural remodeling, accompanied by improved cardiac function. Together, these findings identify AMPK-dependent metabolic remodeling as a state-dependent mechanism of functional rescue in mitochondrial cardiomyopathy.
Esteban Palacios-Contreras, Karen An der Brügge, J. Fell et al.· bioRxiv· 0 citations
Abstract Pancreatic ductal adenocarcinoma (PDAC) remains a formidable clinical challenge. Next-generation protein arginine methyltransferase 5 (PRMT5) inhibitors show promising clinical results in a subset of PDACs with codeletion of the tumor-suppressor CDKN2A and the methylthioadenosine phosphorylase (MTAP) gene, but resistance limits their efficacy. Our study suggests that compensatory spliceosomal reprogramming contributes to adaptation to PRMT5 inhibition. Through comprehensive molecular profiling, we demonstrate that PRMT5 inhibitors induce upregulation of RNA-binding proteins, including RNA-binding protein 39 (RBM39). We investigated whether this response could be therapeutically leveraged by combining PRMT5 inhibition with indisulam-mediated RBM39 degradation, which yielded synergistic activity in cellular model systems. The combination strategy significantly enhanced apoptotic cell death and suppressed tumor outgrowth in resistance assays compared with single-agent treatments. Multiomics analysis revealed concomitant suppression of DNA repair and metabolic pathways. Collectively, our work support spliceosomal rewiring as a candidate adaptive response to PRMT5 inhibition and nominates RBM39 as a candidate therapeutic vulnerability, thereby supporting further evaluation of dual targeting of the splicing machinery. Significance: Our study suggests that compensatory spliceosomal reprogramming occurs in response to PRMT5 inhibition. We investigated this vulnerability by combining PRMT5 inhibition with indisulam-mediated RBM39 degradation, which yielded synergistic antitumor activity in selected cellular PDAC models.
Valentina Spielmann, Jonas Buchloh, Selen Selcen et al.· Cancer Research Communicatio...· 0 citations
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