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CBX4 stabilizes NEUROD1 through SUMO-ubiquitin crosstalk to delay β-cell senescence

ABSTRACT: CBX4 expression is progressively lost in aged and diabetic pancreatic β-cells, correlating with cellular senescence. Mechanistically, CBX4 stabilizes NEUROD1 by promoting its SUMOylation at lysine 38, which antagonizes NEDD4-mediated ubiquitination. Stabilized NEUROD1 enhances insulin transcription and activates CaMKII signaling by suppressing Camk2n1 expression. This cascade preserves mitochondrial function and calcium homeostasis in β-cells. Thus, the STAT5A-CBX4-NEUROD1 axis represents a key protective pathway against β-cell aging and a potential therapeutic target for T2DM.

ORGANISM(S): Mus Musculus

SUBMITTER: Liang Jin

PROVIDER: PXD079253 | iProX | Thu Jun 04 00:00:00 BST 2026

REPOSITORIES: iProX

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Project description:Skeletal muscle mitochondrial dysfunction is secondary to T2DM and can be improved by long-term regular exercise training Mitochondrial dysfunction has long been implicated to play a causative role in development of type 2 diabetes (T2DM). However, a growing number of recent studies provide data that mitochondrial dysfunction is a consequence of T2DM development. The aim of our study is to clarify in further detail the causal role of mitochondrial dysfunction in T2DM by a comprehensive ex vivo analysis of mitochondrial function combined with global gene expression analysis in muscle of pre-diabetic newly diagnosed untreated T2DM subjects and long-standing insulin treated T2DM subjects compared with age- and BMI-matched controls. In addition, we assessed the impact of long-term interval exercise training on physical activity performance, mitochondrial function and glycemic control in long-standing insulin-treated T2DM subjects. Ex vivo mitochondrial density, quality and functioning was comparable between pre-diabetic subjects and matched controls, however, gene expression analysis showed a switch from carbohydrate toward lipids as energy source in pre-diabetes subjects. In contrast, long-term insulin treated T2DM subjects had slightly decreased mitochondrial density and ex vivo function. Expression of Krebs cycle and OXPHOS related genes were decreased, indicating a decreased capacity to use lipids as an energy source. The insulin-treated T2DM subjects had a lower physical activity level than pre-diabetic and normoglycemic subjects. A 52 weeks exercise training of these subjects increased submaximal oxidative efficiency, increased in vivo PCr recovery rate, as well as mildly increased in vitro mitochondrial function. Gene expression of β-oxidation, Krebs cycle and OXPHOS-related genes was increased. Our data demonstrate that mitochondrial dysfunction is rather a consequence than a causative factor in T2DM development as it was only detected in overt diabetes and not in early diabetes. Regular exercise training stabilized exogenous insulin requirement and improved mitochondrial functioning, fatty acid oxidation and general physical work load capacity in long-standing insulin-treated T2DM subjects. As such, the present study shows for the first time that long-term exercise interventions are beneficial in this group of complex diabetes patient and may prevent further metabolic deterioration. Insulin-treated T2DM subjects before and after 52 weeks of exercise training (T2DM_0 and T2DM_52), normoglycemic controls (NGT) and pre-diabetes subjects (IGT) and were selected. RNA was extracted from skeletal muscle biopsies and hybridized on Affymetrix microarrays.

Project description:Diabetic cardiomyopathy (DCM) is a major complication of diabetes mellitus. Excessive activation of the canonical Wnt/β-catenin pathway contributes to the development of cardiomyopathy in type 1 diabetes mellitus (T1DM). Transcription factor 7-like 2 (TCF7L2) is the main β-catenin partner of the TCF family in adult human hearts. In this study, we investigated the role of Wnt/β-catenin in the development of cardiomyopathy in type 2 diabetes mellitus (T2DM) by using streptozotocin (STZ)/high-fat diet (HFD)-induced diabetic mice and high glucose-stimulated neonatal rat cardiomyocytes (NRCMs) as in-vivo and in-vitro models of T2DM, respectively. Compared with the control mice, the T2DM mice exhibited increased myocardial β-catenin and TCF7L2 expression that was concentrated in the nucleus. Treatment of diabetic mice with the β-catenin/TCF7L2 bipartite inhibitor iCRT14 prevented myocardial remodeling and improved cardiac dysfunction. iCRT14 also prevented high glucose-induced hypertrophy in NRCMs, while the β-catenin stabilizer SKL2001 worsened hypertrophy. Immunoprecipitation experiments confirmed the formation of the β-catenin/TCF7L2 bipartite in the control and T2DM mouse cardiomyocytes. Moreover, carbonic anhydrase 2 (CA2) was upregulated in T2DM cardiomyocytes in vitro and in vivo. TCF7L2 overexpression upregulated CA2, while iCRT14 treatment or TCF7L2 knockdown downregulated CA2. Chromatin immunoprecipitation (ChIP) experiments revealed an increased interaction between β-catenin/TCF7L2 and the transcription initiation region of CA2 in the heart tissue of T2DM mice. CA2 knockdown ameliorated NRCM hypertrophy induced by high glucose and SKL2001. A luciferase reporter assay confirmed that CA2 is directly regulated by the β-catenin/TCF7L2 bipartite. Collectively, these results indicate that the canonical Wnt/β-catenin pathway upregulates CA2 via TCF7L2 to promote cardiomyopathy in T2DM. This research sheds new light on the pathogenesis of DCM and presents new potential therapeutic targets for this disease.

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CBX4 stabilizes NEUROD1 through SUMO-ubiquitin crosstalk to delay β-cell senescence

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