FAM210A regulates mitochondrial translation and maintains cardiac mitochondrial homeostasis

AIMS

Mitochondria play a vital role in cellular metabolism and energetics and support normal cardiac function. Disrupted mitochondrial function and homeostasis cause a variety of heart diseases. Fam210a (family with sequence similarity 210 member A), a novel mitochondrial gene, is identified as a hub gene in mouse cardiac remodelling by multi-omics studies. Human FAM210A mutations are associated with sarcopenia. However, the physiological role and molecular function of FAM210A remain elusive in the heart. We aim to determine the biological role and molecular mechanism of FAM210A in regulating mitochondrial function and cardiac health in vivo.

METHODS AND RESULTS

Tamoxifen-induced αMHCMCM-driven conditional knockout of Fam210a in the mouse cardiomyocytes induced progressive dilated cardiomyopathy and heart failure, ultimately causing mortality. Fam210a deficient cardiomyocytes exhibit severe mitochondrial morphological disruption and functional decline accompanied by myofilament disarray at the late stage of cardiomyopathy. Furthermore, we observed increased mitochondrial reactive oxygen species production, disturbed mitochondrial membrane potential, and reduced respiratory activity in cardiomyocytes at the early stage before contractile dysfunction and heart failure. Multi-omics analyses indicate that FAM210A deficiency persistently activates integrated stress response, resulting in transcriptomic, translatomic, proteomic, and metabolomic reprogramming, ultimately leading to pathogenic progression of heart failure. Mechanistically, mitochondrial polysome profiling analysis shows that FAM210A loss of function compromises mitochondrial mRNA translation and leads to reduced mitochondrial-encoded proteins, followed by disrupted proteostasis. We observed decreased FAM210A protein expression in human ischaemic heart failure and mouse myocardial infarction tissue samples. To further corroborate FAM210A function in the heart, AAV9-mediated overexpression of FAM210A promotes mitochondrial-encoded protein expression, improves cardiac mitochondrial function, and partially rescues murine hearts from cardiac remodelling and damage in ischaemia-induced heart failure.

CONCLUSION

These results suggest that FAM210A is a mitochondrial translation regulator to maintain mitochondrial homeostasis and normal cardiomyocyte contractile function. This study also offers a new therapeutic target for treating ischaemic heart disease.

Secondary structures that regulate mRNA translation provide insights for ASO-mediated modulation of cardiac hypertrophy

Translation of upstream open reading frames (uORFs) typically abrogates translation of main (m)ORFs. The molecular mechanism of uORF regulation in cells is not well understood. Here, we data-mined human and mouse heart ribosome profiling analyses and identified a double-stranded RNA (dsRNA) structure within the GATA4 uORF that cooperates with the start codon to augment uORF translation and inhibits mORF translation. A trans-acting RNA helicase DDX3X inhibits the GATA4 uORF-dsRNA activity and modulates the translational balance of uORF and mORF. Antisense oligonucleotides (ASOs) that disrupt this dsRNA structure promote mORF translation, while ASOs that base-pair immediately downstream (i.e., forming a bimolecular double-stranded region) of either the uORF or mORF start codon enhance uORF or mORF translation, respectively. Human cardiomyocytes and mice treated with a uORF-enhancing ASO showed reduced cardiac GATA4 protein levels and increased resistance to cardiomyocyte hypertrophy. We further show the broad utility of uORF-dsRNA- or mORF-targeting ASO to regulate mORF translation for other mRNAs. This work demonstrates that the uORF-dsRNA element regulates the translation of multiple mRNAs as a generalizable translational control mechanism. Moreover, we develop a valuable strategy to alter protein expression and cellular phenotypes by targeting or generating dsRNA downstream of a uORF or mORF start codon.

Secondary structures that regulate mRNA translation provide insights for ASO-mediated modulation of cardiac hypertrophy

Translation of upstream open reading frames (uORFs) typically abrogates translation of main (m)ORFs. The molecular mechanism of uORF regulation in cells is not well understood. Here, we identified a double-stranded RNA (dsRNA) structure residing within the GATA4 uORF that augments uORF translation and inhibits mORF translation. Antisense oligonucleotides (ASOs) that disrupt this dsRNA structure promote mORF translation, while ASOs that base-pair immediately downstream (i.e., forming a bimolecular double-stranded region) of either the uORF or mORF start codon enhance uORF or mORF translation, respectively. Human cardiomyocytes and mice treated with a uORF-enhancing ASO showed reduced cardiac GATA4 protein levels and increased resistance to cardiomyocyte hypertrophy. We further show the general utility of uORF-dsRNA- or mORF- targeting ASO to regulate mORF translation for other mRNAs. Our work demonstrates a regulatory paradigm that controls translational efficiency and a useful strategy to alter protein expression and cellular phenotypes by targeting or generating dsRNA downstream of a uORF or mORF start codon.

Bullet points for discoveries

dsRNA within GATA4 uORF activates uORF translation and inhibits mORF translation. ASOs that target the dsRNA can either inhibit or enhance GATA4 mORF translation. ASOs can be used to impede hypertrophy in human cardiomyocytes and mouse hearts.uORF- and mORF-targeting ASOs can be used to control translation of multiple mRNAs.

FAM210A Regulates Mitochondrial Translation and Maintains Cardiac Mitochondrial Homeostasis

Aims

Mitochondria play a vital role in cellular metabolism and energetics and support normal cardiac function. Disrupted mitochondrial function and homeostasis cause a variety of heart diseases. Fam210a (family with sequence similarity 210 member A), a novel mitochondrial gene, is identified as a hub gene in mouse cardiac remodeling by multi-omics studies. Human FAM210A mutations are associated with sarcopenia. However, the physiological role and molecular function of FAM210A remain elusive in the heart. We aim to determine the biological role and molecular mechanism of FAM210A in regulating mitochondrial function and cardiac health in vivo .

Methods and Results

Tamoxifen-induced αMHC MCM -driven conditional knockout of Fam210a in the mouse cardiomyocytes induced progressive dilated cardiomyopathy and heart failure, ultimately causing mortality. Fam210a deficient cardiomyocytes exhibit severe mitochondrial morphological disruption and functional decline accompanied by myofilament disarray at the late stage of cardiomyopathy. Furthermore, we observed increased mitochondrial reactive oxygen species production, disturbed mitochondrial membrane potential, and reduced respiratory activity in cardiomyocytes at the early stage before contractile dysfunction and heart failure. Multi-omics analyses indicate that FAM210A deficiency persistently activates integrated stress response (ISR), resulting in transcriptomic, translatomic, proteomic, and metabolomic reprogramming, ultimately leading to pathogenic progression of heart failure. Mechanistically, mitochondrial polysome profiling analysis shows that FAM210A loss of function compromises mitochondrial mRNA translation and leads to reduced mitochondrial encoded proteins, followed by disrupted proteostasis. We observed decreased FAM210A protein expression in human ischemic heart failure and mouse myocardial infarction tissue samples. To further corroborate FAM210A function in the heart, AAV9-mediated overexpression of FAM210A promotes mitochondrial-encoded protein expression, improves cardiac mitochondrial function, and partially rescues murine hearts from cardiac remodeling and damage in ischemia-induced heart failure.

Conclusion

These results suggest that FAM210A is a mitochondrial translation regulator to maintain mitochondrial homeostasis and normal cardiomyocyte contractile function. This study also offers a new therapeutic target for treating ischemic heart disease.

Translational Perspective

Mitochondrial homeostasis is critical for maintaining healthy cardiac function. Disruption of mitochondrial function causes severe cardiomyopathy and heart failure. In the present study, we show that FAM210A is a mitochondrial translation regulator required for maintaining cardiac mitochondrial homeostasis in vivo . Cardiomyocyte-specific FAM210A deficiency leads to mitochondrial dysfunction and spontaneous cardiomyopathy. Moreover, our results indicate that FAM210A is downregulated in human and mouse ischemic heart failure samples and overexpression of FAM210A protects hearts from myocardial infarction induced heart failure, suggesting that FAM210A mediated mitochondrial translation regulatory pathway can be a potential therapeutic target for ischemic heart disease.

FAM114A1 influences cardiac pathological remodeling by regulating angiotensin II signaling

Cardiac pathological remodeling, a primary contributor to heart failure (HF) and death, is an important target for HF therapy. However, the signaling pathways that govern cardiac remodeling are not fully elucidated. Here, we found that a functionally unannotated human myocardial infarction–associated (MI-associated) gene, family with sequence similarity 114 member A1 (FAM114A1), is induced in failing human and mouse hearts compared with nonfailing hearts. Homozygous KO of Fam114a1 (Fam114a1^–/–) in the mouse genome reduces cardiomyocyte hypertrophy, inflammation, and cardiac fibrosis while restoring cardiac function in angiotensin II–induced (Ang II–induced) and MI-induced HF mouse models. Cardiac fibroblasts (CFs) exhibit the highest FAM114A1 expression among different cardiac cell types. FAM114A1 is a critical autonomous factor for CF proliferation, activation, and migration. Mechanistically, FAM114A1 interacts with angiotensin receptor–associated protein (AGTRAP) and regulates the expression of angiotensin type 1 receptor (AT1R) and downstream Ang II signaling transduction, and it subsequently influences profibrotic response. Our results indicate that FAM114A1 regulates Ang II signaling, thereby activating CFs and other cardiac cells and augmenting pathological cardiac remodeling. These findings provide potentially novel insights into the regulation of cardiac remodeling and identify FAM114A1 as a therapeutic target for the treatment of heart disease.

MicroRNA-574 regulates FAM210A expression and influences pathological cardiac remodeling

Aberrant expression of mitochondrial proteins impairs cardiac function and causes heart disease. The mechanism of regulation of mitochondria encoded protein expression during cardiac disease, however, remains underexplored. Here, we show that multiple pathogenic cardiac stressors induce the expression of miR-574 guide and passenger strands (miR-574-5p/3p) in both humans and mice. miR-574 knockout mice exhibit severe cardiac disorder under different pathogenic cardiac stresses while miR-574-5p/3p mimics that are delivered systematically using nanoparticles reduce cardiac pathogenesis under disease insults. Transcriptomic analysis of miR-574-null hearts uncovers family with sequence similarity 210 member A (FAM210A) as a common target mRNA of miR-574-5p and miR-574-3p. The interactome capture analysis suggests that FAM210A interacts with mitochondrial translation elongation factor EF-Tu. Manipulating miR-574-5p/3p or FAM210A expression changes the protein expression of mitochondrial-encoded electron transport chain (ETC) genes but not nuclear-encoded mitochondrial ETC genes in both human AC16 cardiomyocyte cells and miR-574-null murine hearts. Together, we discovered that miR-574 regulates FAM210A expression and modulates mitochondrial-encoded protein expression, which may influence cardiac remodeling in heart failure.

Glutamyl-Prolyl-tRNA Synthetase Regulates Proline-Rich Pro-Fibrotic Protein Synthesis During Cardiac Fibrosis

RATIONALE

Increased protein synthesis of profibrotic genes is a common feature in cardiac fibrosis and heart failure. Despite this observation, critical factors and molecular mechanisms for translational control of profibrotic genes during cardiac fibrosis remain unclear.

OBJECTIVE

To investigate the role of a bifunctional ARS (aminoacyl-tRNA synthetase), EPRS (glutamyl-prolyl-tRNA synthetase) in translational control of cardiac fibrosis.

METHODS AND RESULTS

Results from reanalyses of multiple publicly available data sets of human and mouse heart failure, demonstrated that EPRS acted as an integrated node among the ARSs in various cardiac pathogenic processes. We confirmed that EPRS was induced at mRNA and protein levels (≈1.5-2.5-fold increase) in failing hearts compared with nonfailing hearts using our cohort of human and mouse heart samples. Genetic knockout of one allele of Eprs globally (Eprs+/-) using CRISPR-Cas9 technology or in a Postn-Cre-dependent manner (Eprsflox/+; PostnMCM/+) strongly reduces cardiac fibrosis (≈50% reduction) in isoproterenol-, transverse aortic constriction-, and myocardial infarction (MI)-induced heart failure mouse models. Inhibition of EPRS using a PRS (prolyl-tRNA synthetase)-specific inhibitor, halofuginone, significantly decreases translation efficiency (TE) of proline-rich collagens in cardiac fibroblasts as well as TGF-β (transforming growth factor-β)-activated myofibroblasts. Overexpression of EPRS increases collagen protein expression in primary cardiac fibroblasts under TGF-β stimulation. Using transcriptome-wide RNA-Seq and polysome profiling-Seq in halofuginone-treated fibroblasts, we identified multiple novel Pro-rich genes in addition to collagens, such as Ltbp2 (latent TGF-β-binding protein 2) and Sulf1 (sulfatase 1), which are translationally regulated by EPRS. SULF1 is highly enriched in human and mouse myofibroblasts. In the primary cardiac fibroblast culture system, siRNA-mediated knockdown of SULF1 attenuates cardiac myofibroblast activation and collagen deposition. Overexpression of SULF1 promotes TGF-β-induced myofibroblast activation and partially antagonizes anti-fibrotic effects of halofuginone treatment.

CONCLUSIONS

Our results indicate that EPRS preferentially controls translational activation of proline codon rich profibrotic genes in cardiac fibroblasts and augments pathological cardiac remodeling. Graphical Abstract: A graphical abstract is available for this article.

Mammalian RNA switches: Molecular rheostats in gene regulation, disease, and medicine

Alteration of RNA structure by environmental signals is a fundamental mechanism of gene regulation. For example, the riboswitch is a noncoding RNA regulatory element that binds a small molecule and causes a structural change in the RNA, thereby regulating transcription, splicing, or translation of an mRNA. The role of riboswitches in metabolite sensing and gene regulation in bacteria and other lower species was reported almost two decades ago, but riboswitches have not yet been discovered in mammals. An analog of the riboswitch, the protein-directed RNA switch (PDRS), has been identified as an important regulatory mechanism of gene expression in mammalian cells. RNA-binding proteins and microRNAs are two major executors of PDRS via their interaction with target transcripts in mammals. These protein-RNA interactions influence cellular functions by integrating environmental signals and intracellular pathways from disparate stimuli to modulate stability or translation of specific mRNAs. The discovery of a riboswitch in eukaryotes that is composed of a single class of thiamine pyrophosphate (TPP) suggests that additional ligand-sensing RNAs may be present to control eukaryotic or mammalian gene expression. In this review, we focus on protein-directed RNA switch mechanisms in mammals. We offer perspectives on the potential discovery of mammalian protein-directed and compound-dependent RNA switches that are related to human disease and medicine.

Abstract 327: MicroRNA-574-FAM210A Axis Maintains Mitochondrial Translational Homeostasis and Influences Pathological Cardiac Remodeling

Rationale: Translational control is a critical regulatory step in altering protein synthesis under disease conditions. Aberrant synthesis of mitochondrial proteins impairs cardiac function and causes heart disease. However, the mechanism of translational control in mitochondria and during cardiac disease remains underexplored.

Objective: We have found that multiple pathogenic cardiac stressors induce the expression of miR-574 guide and passenger strands (miR-574-5p/3p) in humans and mice. Here, we aim to define a new miR-574-FAM210A axis that regulates cardiac mitochondrial translational homeostasis and prevents adverse cardiac remodeling.

Methods and Results: Echocardiography, histology and biochemical analyses were used to evaluate the cardiac function of miR-574 knockout mice, which exhibit severe cardiac hypertrophy, fibrosis, and cardiac dysfunction under heart failure-triggering stresses. miR-574-5p/3p mimics that were delivered systematically using nanoparticles reduced cardiac pathogenesis with disease insults. Transcriptome analysis of miR-574-null hearts has uncovered FAM210A as a common target mRNA for miR-574-5p/3p. Interactome and translational state analyses identify a FAM210A-bearing trimeric complex that promotes the translation of mitochondrial encoded electron transport chain genes and modulates mitochondrial activities. Moreover, the phenotypic characterization of tamoxifen-inducible CM-specific Fam210a knockout mice suggests that FAM210A plays a critical role in maintaining normal cardiac mitochondrial morphology and function as well as cardiac health and organismal viability.

Conclusions: miR-574-5p and miR-574-3p protect against pathological cardiac remodeling through regulation of FAM210A, a key translational control factor of mitochondrial encoded genes. Thus, we discovered a novel miR-574-FAM210A pathway that modulates cardiac mitochondrial translational homeostasis and influences cardiac remodeling in heart failure.

Abstract 264: EPRS is a Critical Translational Control Factor in Cardiac Fibrosis

Increased protein synthesis of pro-fibrotic genes is a common feature of cardiac fibrosis, a major manifestation of heart failure (HF). Despite this observation, critical factors and molecular mechanisms for translational control of cardiac fibrosis remain underexplored. Here, we identify a critical house-keeping translational regulator, glutamyl-prolyl-tRNA synthetase (EPRS), which preferentially regulates the translation of proline-rich (PRR) pro-fibrotic genes. In mammals, EPRS catalyzes the attachment of two amino acids, glutamic acid and proline, to their cognate tRNAs for protein synthesis. By overlapping of aminoacyl-tRNA synthetases (ARSs) induced in TGF-β treated human cardiac fibroblasts, human ARSs with genetic mutations in the congenital heart disease, mouse ARSs associated with isoproterenol (ISO)-induced cardiomyopathy by GWAS, and ISO-induced ARSs in mouse failing hearts, we identified EPRS as the only ARS involved in various cardiac pathogenesis. EPRS is induced in failing human heart compared to non-failing donor heart and functions as an integrated node downstream of multiple hypertrophic and fibrotic stimuli in murine hearts, including ISO infusion and transverse aortic constriction (TAC) surgery. Low-dose halofuginone (Halo), a prolyl-tRNA synthetase (PRS)-specific inhibitor, as well as genetic knockout of one allele of EPRS in mouse genome, reduces cardiac hypertrophy and fibrosis in ISO- and TAC-induced HF mouse models. Using RNA-Seq and polysome profiling-Seq in Halo-treated fibroblasts, we identified several novel PRR genes, including Ltbp2, Furin and Sulf1, in addition to collagens, which are translationally regulated by EPRS. Inhibition of Furin by various inhibitors attenuates cardiac fibroblast activation and collagen deposition in vitro . Finally, we found that inactivation of EPRS reduced translational efficiency and enhanced mRNA decay of PRR genes. Taken together, our results indicate that EPRS controls the translational activation of PRR genes in cardiac fibroblasts, and these data provide novel insights into the translational control mechanisms of cardiac fibrosis, which may promote development of novel therapeutics by inhibiting pro-fibrotic translation factors.

hnRNP L-mediated RNA switches function as a hypoxia-induced translational regulon

The GAIT (gamma-interferon-activated inhibitor of translation) complex or miR-297-RISC (RNA-induced silencing complex), together with hnRNP L or hnRNP L-bearing complex, operates an RNA switch in myeloid cells that regulates stress-dependent expression of vascular endothelial growth factor-A (VEGFA). Here, we have shown that hnRNP L directs multiple hypoxia-inducible RNA switches simultaneously and regulates expression of these oncogenic genes in addition to VEGFA. Bioinformatic and polysome profiling-microarray screens have identified DNM1L (Dynamin 1-like) and PHF21A (PHD finger protein 21A) mRNAs as regulated at the translational level by GAIT-dependent, hnRNP L-directed RNA switches. We have also uncovered CDK6 (Cyclin dependent kinase 6), MKLN1 (Muskelin 1) and EIF5 (Eukaryotic initiation factor 5) as novel miR-297-dependent, hnRNP L-directed RNA switch transcripts. Src Kinase is required for the phosphorylation of hnRNP L and activation of the RNA switch pathway. Knockdown of hnRNP L sensitizes the human U937 monocytic cells under hypoxia stress but not in normoxia via inducing cell apoptosis partially due to the reduced translation of hnRNP L target mRNAs. Collectively, our findings suggest that commonly controlled genes by the hnRNP L-directed RNA switches form a translational regulon that promotes hypoxia resistance and cell survival.

Design, Synthesis and Biological Evaluation of Novel Phosphorylated Abacavir Derivatives as Antiviral Agents Against Newcastle Disease Virus Infection in Chicken

Newcastle disease virus is the most devastating virus in poultry industry. It can eradicate the entire poultry flocks once infected. This study is aimed to investigate the antiviral efficacy of novel phosphorylated analogues of the drug abacavir (ABC) against Newcastle disease virus (NDV). About 16 analogues of ABC were designed and docking was performed against fusion protein of NDV. Three compounds were identified and selected for synthesis and biological evaluation based on binding affinity and docking scores. The compounds were synthesized and characterized by IR, (1)H, (13)C, (31)P and CHN analysis and mass spectra. These compounds were tested for antiviral efficacy against NDV-infected DF-1 cells. Compound ABC-1 had shown potent antiviral activity as evidenced by significant reduction in plaque units and cytopathic effect. Therefore, ABC-1 was selected to test for NDV-infected chicken survival rate. Effective dose50 concentrations were determined for ABC-1. Antioxidant enzyme levels in brain, liver and lung tissues were estimated. Superoxide dismutase and catalase were significantly raised and lipid peroxidation and HA titer levels were decreased upon treatment with 2 mg/kg body weight ABC-1. Histopathological modifications were also restored in the ABC-1-treated group. These findings demonstrated ABC-1 as a potential antiviral agent against NDV in chicken.

Solanum torvum Swartz. fruit attenuates cadmium-induced liver and kidney damage through modulation of oxidative stress and glycosylation

Increased levels of environmental pollutants are linked to almost all human disorders; the efficient method to manage the human health is through naturally available dietary molecule. Solanum torvum (ST) Swartz (Solanaceae) commonly called Turkey Berry is found in Africa, Asia, and South America. Its fruit, part of traditional Indian cuisine, is a widely consumed nutritious herb, acclaimed for its medicinal value. ST aqueous extract (STAe) (250, 500, and 1000 mg/kg b.w., 6 days; oral) against acute Cadmium (Cd) (6.3 mg/kg b.w., single dose; oral) toxicity was evaluated in rats. Protective effect was assessed using serum markers, tissue antioxidants, oxidant derivatives, glycoprotein, and histopathological studies. The activities of serum marker enzymes were increased (40-60 %); antioxidant enzymes such as SOD and CAT, GSH, and its metabolic enzyme activities were decreased (50-80 %) in the liver and kidney upon Cd intoxication. During STAe pre-treatment, at doses of 250 and 500 mg/kg b.w., the above changes were brought to near normal (25-63 %). Tissue 4-hydroxynonenal, 3-nitrotyrosine, and protein carbonyls were increased (8-15 fold) in Cd-alone-treated rats, whereas pre-supplementation of STAe significantly decreased their levels and inhibited the protein glycosylation effectively. The pharmacological effect of STAe was confirmed by histopathological observations. Based on previous literature and present investigation, we conclude that ST may serve as a potential functional food against environmental contaminant such as heavy metal-induced oxidative stress.

Newcastle disease virus (NDV) induces protein oxidation and nitration in brain and liver of chicken: Ameliorative effect of vitamin E

The present study was aimed at investigating the therapeutic efficacy of vitamin E on oxidative injury in brain and liver of Newcastle disease virus (NDV) challenged chickens. We have analyzed the xanthine oxidase (XOD) activity; uric acid (UA) levels and superoxide radical generation by using electron spin resonance spectroscopy. Further, protein oxidation, nitration and apoptosis were evaluated in the brain and liver of the control, NDV-infected and NDV+Vit. E treated groups. A significant elevation was observed in XOD activity and UA levels in brain (p<0.001) and liver (p<0.05) of NDV infected birds when compared to controls. Further, significant increase in the production of superoxides, enhanced intracellular protein carbonyls and nitrates were observed in the brain and liver of NDV-infected birds over healthy subjects. Apoptosis studies also suggested that a larger number of TUNEL positive cells were observed in brain and a moderately in liver of NDV-infected chickens. However, all these perturbations were significantly ameliorated in NDV+Vit. E treated chickens as compared to NDV-infected birds. Taken together, our results suggested that NDV-induced neuronal and hepatic damage at least in part mediates oxidative stress and on the other hand, supplementation of vitamin E mitigates NDV-induced oxidative damage thereby protects brain and liver of chickens. These findings could provide new insights into the understanding of NDV pathogenesis and therapeutic effects of dietary antioxidants.