Selenoprotein DIO2 Is a Regulator of Mitochondrial Function, Morphology and UPRmt in Human Cardiomyocytes

Abstract

Members of the fetal-gene-program may act as regulatory components to impede deleterious events occurring with cardiac remodeling, and constitute potential novel therapeutic heart failure (HF) targets. Mitochondrial energy derangements occur both during early fetal development and in patients with HF. Here we aim to elucidate the role of DIO2, a member of the fetal-gene-program, in pluripotent stem cell (PSC)-derived human cardiomyocytes and on mitochondrial dynamics and energetics, specifically. RNA sequencing and pathway enrichment analysis was performed on mouse cardiac tissue at different time points during development, adult age, and ischemia-induced HF. To determine the function of DIO2 in cardiomyocytes, a stable human hPSC-line with a DIO2 knockdown was made using a short harpin sequence. Firstly, we showed the selenoprotein, type II deiodinase (DIO2): the enzyme responsible for the tissue-specific conversion of inactive (T4) into active thyroid hormone (T3), to be a member of the fetal-gene-program. Secondly, silencing DIO2 resulted in an increased reactive oxygen species, impaired activation of the mitochondrial unfolded protein response, severely impaired mitochondrial respiration and reduced cellular viability. Microscopical 3D reconstruction of the mitochondrial network displayed substantial mitochondrial fragmentation. Summarizing, we identified DIO2 to be a member of the fetal-gene-program and as a key regulator of mitochondrial performance in human cardiomyocytes. Our results suggest a key position of human DIO2 as a regulator of mitochondrial function in human cardiomyocytes.

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“…Proteins were isolated from snap-frozen LVs using radioimmunoprecipitation assay (RIPA) lysis buffer as previously described [ 41 ]. Protein samples were centrifuged at 12,000× g for 10 min at 4 °C, and the supernatant containing soluble proteins was collected.…”

Relationship between selenium status, selenoproteins and COVID-19 and other inflammatory diseases: A critical review

“…Recently, it was demonstrated DIO2 silencing (50% reduction in the DIO2 protein) in human cardiomyocytes derived from pluripotent cells caused oxidative stress and impaired mitochondrial function [141] . The effects of DIO2 deficiency in mitochondria was related to non-adequate fold of mitochondrial proteins, particularly those associated with respiratory chain complexes [146] . Although the pro-oxidant consequences of down-regulation of DIO2 protein synthesis was indirectly mediated by mitochondrial dysfunction, a potential direct antioxidant effect of DIO2 was not investigated.…”

Micronutrient deficiencies in heart failure: Mitochondrial dysfunction as a common pathophysiological mechanism?

“…Proteins from the GPX and TXNRD families are crucial antioxidant (redox) enzymes involved in preventing the harmful accumulation of intracellular hydrogen peroxide, including in the mitochondria [35,36]. DIOs regulate the local bioactivity of thyroid hormone, which stimulates mitochondrial biogenesis, increasing myocardial mitochondrial mass, mitochondrial respiration, oxidative phosphorylation, enzyme activities, mitochondrial protein synthesis, cytochrome, phospholipid and mitochondrial DNA (mtDNA) content [32,92]. The human selenoproteome also includes methionine sulfoxide reductase B1 (MSRB1), which promotes antiinflammatory cytokine expression and controls the immune response [39].…”