Mitochondrial fission process 1 (MTFP1) controls bioenergetic efficiency and prevents inflammatory cardiomyopathy and heart failure in mice

Mitochondria are paramount to the metabolism and survival of cardiomyocytes. Here we show that Mitochondrial Fission Process 1 (MTFP1) is essential for cardiac structure and function. Constitutive knockout of cardiomyocyte MTFP1 in mice resulted in adult-onset dilated cardiomyopathy (DCM) characterized by sterile inflammation and cardiac fibrosis that progressed to heart failure and middle-aged death. Failing hearts from cardiomyocyte-restricted knockout mice displayed a general decline in mitochondrial gene expression and oxidative phosphorylation (OXPHOS) activity. Pre-DCM, we observed no defects in mitochondrial morphology, content, gene expression, OXPHOS assembly nor phosphorylation dependent respiration. However, knockout cardiac mitochondria displayed reduced membrane potential and increased non-phosphorylation dependent respiration, which could be rescued by pharmacological inhibition of the adenine nucleotide translocase ANT. Primary cardiomyocytes from pre-symptomatic knockout mice exhibited normal excitation-contraction coupling but increased sensitivity to programmed cell death (PCD), which was accompanied by an opening of the mitochondrial permeability transition pore (mPTP). Intriguingly, mouse embryonic fibroblasts deleted for Mtfp1 recapitulated PCD sensitivity and mPTP opening, both of which could be rescued by pharmacological or genetic inhibition of the mPTP regulator Cyclophilin D. Collectively, our data demonstrate that contrary to previous in vitro studies, the loss of the MTFP1 promotes mitochondrial uncoupling and increases cell death sensitivity, causally mediating pathogenic cardiac remodeling.


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Thus, MTFP1 is dispensable for mitochondrial dynamics in the heart.

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In light of these surprising findings, we decided to measure mitochondrial morphology in MEFs

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To define the molecular mechanisms underlying the increased sensitivity PCD and mPTP opening 373 caused by MTFP1 ablation, we used WT and Mtfp1 -/-MEFs. We began by confirming that like

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Proton leak has marked influence on energy metabolism. Enhancement of this process in various 535 tissues can counteract the deleterious effects of nutrient overload via UCP1-dependent and 536 independent pathways (Roesler and Kazak, 2020) and thus may be beneficial in some settings. In 537 the heart, whose bioenergetic efficiency has evolved to maximize ATP output, excessive proton 538 leak has been shown to drive age-related cardiomyocyte and cardiac dysfunction in mice (Chiao et  ANT-dependent proton leak is increased in cardiomyocytes from old, but not young mice and can 541 be rejuvenated by blocking ANT and reducing sensitivity to mPTP opening.

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In line with the notion that increased proton leak is maladaptive for the heart, our study shows for 543 the first time that MTFP1 loss in cardiomyocytes reduces the mitochondrial membrane potential as

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In summary our study reveals new and essential roles of MTFP1 in cardiac homeostasis that are 558 distinct from its previously reported impact on mitochondrial fission, the latter of which our data 559 conclusively show is unaffected in vitro and in vivo. Thus, our work now positions MTFP1 as a 560 critical regulator of mitochondrial coupling through ANT in cardiomyocytes and its loss leads to 561 membrane potential dissipation associated to mPTP opening, cell death and progressive DCM that 562 leads to heart failure and middle-aged death. These findings advance our understanding of the 563 mitochondrial defects that can trigger the development of dilated cardiomyopathy and heart failure.

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We propose that MTFP1 to be a valuable tool for the molecular dissection of mitochondrial 565 uncoupling and mPTP function and thus a promising target to mitigate the pathological events of 566 cardiac and metabolic remodeling in heart disease.                                                            were i) field-stimulated at 0.5 Hz, ii) exposed to the β-adrenergic agonist isoproterenol and iii) 867 stimulated at frequency of 5 Hz, iv) and then stepped back to 0.5 Hz washing out (wo)

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In the native state, transcription is aborted at the insulator site (H19, black), and instead started at        Once the thorax was opened, the descending aorta was cut and the heart exposed and flushed

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The following search parameters were applied: carbamidomethylation of cysteines was set as a 1483 fixed modification, oxidation of methionine and protein N-terminal acetylation were set as variable 1484 modifications. The mass tolerances in MS and MS/MS were set to 5 ppm and 20 ppm respectively.

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Maximum peptide charge was set to 7 and 5 amino acids were required as minimum peptide 1486 length. A false discovery rate of 1% was set up for both protein and peptide levels. The iBAQ 1487 intensity was used to estimate the protein abundance within a sample. The match between runs 1488 features was allowed for biological replicate only.