Elevated levels of Letm1 drives mitochondrial dysfunction and cardiomyocyte stress-mediated apoptosis in cultured cardiomyocytes
Abstract Background Cardiac ischemia, a predominant cause of heart failure, is marked by profound mitochondrial dysfunction, dysregulated ion homeostasis, and maladaptive cellular remodeling, all of which compromise cardiac performance. The mitochondrial inner membrane protein Leucine zipper-EF-hand...
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BMC
2025-08-01
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| Series: | Cell Communication and Signaling |
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| Online Access: | https://doi.org/10.1186/s12964-025-02378-7 |
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| author | Anushka Deshpande Leo Weirauch Tapan Kumar Baral Marco Steier Ankush Borlepawar Manju Kumari Lucia S. Kilian Karsten Richter Elke Hammer Derk Frank Constanze Schmidt Norbert Frey Ashraf Y. Rangrez |
| author_facet | Anushka Deshpande Leo Weirauch Tapan Kumar Baral Marco Steier Ankush Borlepawar Manju Kumari Lucia S. Kilian Karsten Richter Elke Hammer Derk Frank Constanze Schmidt Norbert Frey Ashraf Y. Rangrez |
| author_sort | Anushka Deshpande |
| collection | DOAJ |
| description | Abstract Background Cardiac ischemia, a predominant cause of heart failure, is marked by profound mitochondrial dysfunction, dysregulated ion homeostasis, and maladaptive cellular remodeling, all of which compromise cardiac performance. The mitochondrial inner membrane protein Leucine zipper-EF-hand containing Transmembrane Protein 1 (Letm1), implicated in Wolf-Hirschhorn Syndrome, is essential for mitochondrial function. Although genetic alterations in Letm1 are linked to cardiomyopathies, its specific contributions to cardiac pathophysiology, particularly in the context of ischemic heart disease, remain poorly defined. This study aims to elucidate the role of Letm1 in ischemic cardiac pathology and its mechanistic impact on cardiomyocyte function. Methods Letm1 expression was assessed in human and murine models of heart failure due to ischemic cardiomyopathy (ICM) and cardiac hypertrophy. Letm1 was overexpressed in neonatal rat ventricular cardiomyocytes, adult mouse cardiomyocytes, and human induced pluripotent stem cell (iPSC)-derived cardiomyocytes to study mitochondrial function (Seahorse assays), structural and molecular remodeling (fluorescence microscopy, transmission electron microscopy (TEM), qPCR, immunoblotting), transcriptomic/proteomic profiles, calcium handling and electrophysiology (patch-clamp), autophagic flux (Bafilomycin A1, LC3-RFP-GFP), and cell survival. Results Letm1 was markedly upregulated in ICM in both human and murine hearts, but unchanged in hypertrophic heart failure. Overexpression of Letm1 in cardiomyocytes resulted in profound mitochondrial dysfunction, including downregulation of oxidative phosphorylation (OXPHOS) genes, impaired membrane potential, reduced ATP output, increased proton leak, and elevated ROS levels. A metabolic shift toward glycolysis was observed, accompanied by reduced fatty acid oxidation. Electron microscopy revealed mitochondrial fragmentation, mitophagic vesicles, and sarcomeric disarray. Transcriptomic and proteomic analyses highlighted dysregulation of genes linked to mitochondrial organization, ion transport, and autophagy. Electrophysiologically, Letm1 reduced L-type Ca2+ current density and significantly shortened action potential duration, leading to impaired contractility. Letm1 overexpression activated upstream autophagy regulators (AMPK, ULK1) and enhanced LC3-II and p62 accumulation, but autophagic flux was impaired, as confirmed by LC3-RFP-GFP reporter and exacerbated by Bafilomycin A1 treatment. This dysregulated autophagy was coupled with mitochondrial stress, increased apoptosis (cleaved caspases), and reduced cardiomyocyte viability. Conclusion This study indicates that Letm1 upregulation drives mitochondrial dysfunction, electrophysiology alterations, and activation of autophagy and apoptosis, culminating in cardiomyocyte injury in ischemic cardiomyopathy. By disrupting OXPHOS, calcium handling, and cell survival pathways, Letm1 contributes to ischemic remodeling and cardiac dysfunction. Targeting Letm1 presents a promising therapeutic strategy to alleviate ischemic damage and preserve cardiac function. Graphical abstract This graphical abstract illustrates the multifaceted effects of elevated levels of Leucine zipper-EF-hand-containing transmembrane protein 1 (Letm1) on cardiomyocyte function. Increased Letm1 disrupts mitochondrial oxidative phosphorylation (OXPHOS), leading to energy supply deficits, mitochondrial dysregulation, and impaired ion channel activity. These alterations contribute to electrophysiological deficits and compromise cardiac action potential. Simultaneously, mitochondrial dysfunction accelerates autophagy and apoptosis, further diminishing cell survival. Together, these mechanisms drive contractile dysfunction in neonatal rat ventricular cardiomyocytes (NRVCMs), highlighting a critical role for Letm1 in cardiac pathophysiology. |
| format | Article |
| id | doaj-art-b8d85a87ed0945cf8c31e22247cc2b62 |
| institution | Kabale University |
| issn | 1478-811X |
| language | English |
| publishDate | 2025-08-01 |
| publisher | BMC |
| record_format | Article |
| series | Cell Communication and Signaling |
| spelling | doaj-art-b8d85a87ed0945cf8c31e22247cc2b622025-08-24T11:41:07ZengBMCCell Communication and Signaling1478-811X2025-08-0123112410.1186/s12964-025-02378-7Elevated levels of Letm1 drives mitochondrial dysfunction and cardiomyocyte stress-mediated apoptosis in cultured cardiomyocytesAnushka Deshpande0Leo Weirauch1Tapan Kumar Baral2Marco Steier3Ankush Borlepawar4Manju Kumari5Lucia S. Kilian6Karsten Richter7Elke Hammer8Derk Frank9Constanze Schmidt10Norbert Frey11Ashraf Y. Rangrez12Department of Cardiology, Angiology and Pneumology, Internal Medicine III, University Hospital HeidelbergDepartment of Cardiology, Angiology and Pneumology, Internal Medicine III, University Hospital HeidelbergDepartment of Cardiology, Angiology and Pneumology, Internal Medicine III, University Hospital HeidelbergDepartment of Cardiology, Angiology and Pneumology, Internal Medicine III, University Hospital HeidelbergMedical schoolDepartment of Cardiology, Angiology and Pneumology, Internal Medicine III, University Hospital HeidelbergDepartment of Cardiology and Internal Intensive Medicine, Internal Medicine III, University Hospital of Schleswig-HolsteinCore Facility Electron Microscopy, German Cancer Research Center (DKFZ)Interfaculty Institute of Genetics and Functional Genomics, University Medicine GreifswaldDepartment of Cardiology and Internal Intensive Medicine, Internal Medicine III, University Hospital of Schleswig-HolsteinDepartment of Cardiology, Angiology and Pneumology, Internal Medicine III, University Hospital HeidelbergDepartment of Cardiology, Angiology and Pneumology, Internal Medicine III, University Hospital HeidelbergDepartment of Cardiology, Angiology and Pneumology, Internal Medicine III, University Hospital HeidelbergAbstract Background Cardiac ischemia, a predominant cause of heart failure, is marked by profound mitochondrial dysfunction, dysregulated ion homeostasis, and maladaptive cellular remodeling, all of which compromise cardiac performance. The mitochondrial inner membrane protein Leucine zipper-EF-hand containing Transmembrane Protein 1 (Letm1), implicated in Wolf-Hirschhorn Syndrome, is essential for mitochondrial function. Although genetic alterations in Letm1 are linked to cardiomyopathies, its specific contributions to cardiac pathophysiology, particularly in the context of ischemic heart disease, remain poorly defined. This study aims to elucidate the role of Letm1 in ischemic cardiac pathology and its mechanistic impact on cardiomyocyte function. Methods Letm1 expression was assessed in human and murine models of heart failure due to ischemic cardiomyopathy (ICM) and cardiac hypertrophy. Letm1 was overexpressed in neonatal rat ventricular cardiomyocytes, adult mouse cardiomyocytes, and human induced pluripotent stem cell (iPSC)-derived cardiomyocytes to study mitochondrial function (Seahorse assays), structural and molecular remodeling (fluorescence microscopy, transmission electron microscopy (TEM), qPCR, immunoblotting), transcriptomic/proteomic profiles, calcium handling and electrophysiology (patch-clamp), autophagic flux (Bafilomycin A1, LC3-RFP-GFP), and cell survival. Results Letm1 was markedly upregulated in ICM in both human and murine hearts, but unchanged in hypertrophic heart failure. Overexpression of Letm1 in cardiomyocytes resulted in profound mitochondrial dysfunction, including downregulation of oxidative phosphorylation (OXPHOS) genes, impaired membrane potential, reduced ATP output, increased proton leak, and elevated ROS levels. A metabolic shift toward glycolysis was observed, accompanied by reduced fatty acid oxidation. Electron microscopy revealed mitochondrial fragmentation, mitophagic vesicles, and sarcomeric disarray. Transcriptomic and proteomic analyses highlighted dysregulation of genes linked to mitochondrial organization, ion transport, and autophagy. Electrophysiologically, Letm1 reduced L-type Ca2+ current density and significantly shortened action potential duration, leading to impaired contractility. Letm1 overexpression activated upstream autophagy regulators (AMPK, ULK1) and enhanced LC3-II and p62 accumulation, but autophagic flux was impaired, as confirmed by LC3-RFP-GFP reporter and exacerbated by Bafilomycin A1 treatment. This dysregulated autophagy was coupled with mitochondrial stress, increased apoptosis (cleaved caspases), and reduced cardiomyocyte viability. Conclusion This study indicates that Letm1 upregulation drives mitochondrial dysfunction, electrophysiology alterations, and activation of autophagy and apoptosis, culminating in cardiomyocyte injury in ischemic cardiomyopathy. By disrupting OXPHOS, calcium handling, and cell survival pathways, Letm1 contributes to ischemic remodeling and cardiac dysfunction. Targeting Letm1 presents a promising therapeutic strategy to alleviate ischemic damage and preserve cardiac function. Graphical abstract This graphical abstract illustrates the multifaceted effects of elevated levels of Leucine zipper-EF-hand-containing transmembrane protein 1 (Letm1) on cardiomyocyte function. Increased Letm1 disrupts mitochondrial oxidative phosphorylation (OXPHOS), leading to energy supply deficits, mitochondrial dysregulation, and impaired ion channel activity. These alterations contribute to electrophysiological deficits and compromise cardiac action potential. Simultaneously, mitochondrial dysfunction accelerates autophagy and apoptosis, further diminishing cell survival. Together, these mechanisms drive contractile dysfunction in neonatal rat ventricular cardiomyocytes (NRVCMs), highlighting a critical role for Letm1 in cardiac pathophysiology.https://doi.org/10.1186/s12964-025-02378-7Letm1Mitochondrial metabolismCardiomyocytesHypertrophyArrhythmias |
| spellingShingle | Anushka Deshpande Leo Weirauch Tapan Kumar Baral Marco Steier Ankush Borlepawar Manju Kumari Lucia S. Kilian Karsten Richter Elke Hammer Derk Frank Constanze Schmidt Norbert Frey Ashraf Y. Rangrez Elevated levels of Letm1 drives mitochondrial dysfunction and cardiomyocyte stress-mediated apoptosis in cultured cardiomyocytes Cell Communication and Signaling Letm1 Mitochondrial metabolism Cardiomyocytes Hypertrophy Arrhythmias |
| title | Elevated levels of Letm1 drives mitochondrial dysfunction and cardiomyocyte stress-mediated apoptosis in cultured cardiomyocytes |
| title_full | Elevated levels of Letm1 drives mitochondrial dysfunction and cardiomyocyte stress-mediated apoptosis in cultured cardiomyocytes |
| title_fullStr | Elevated levels of Letm1 drives mitochondrial dysfunction and cardiomyocyte stress-mediated apoptosis in cultured cardiomyocytes |
| title_full_unstemmed | Elevated levels of Letm1 drives mitochondrial dysfunction and cardiomyocyte stress-mediated apoptosis in cultured cardiomyocytes |
| title_short | Elevated levels of Letm1 drives mitochondrial dysfunction and cardiomyocyte stress-mediated apoptosis in cultured cardiomyocytes |
| title_sort | elevated levels of letm1 drives mitochondrial dysfunction and cardiomyocyte stress mediated apoptosis in cultured cardiomyocytes |
| topic | Letm1 Mitochondrial metabolism Cardiomyocytes Hypertrophy Arrhythmias |
| url | https://doi.org/10.1186/s12964-025-02378-7 |
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