Mitofusin-2 (Mfn-2) is a dynamin-like protein that involved in the rearrangement of outer mitochondrial membrane. Research using various experimental systems has shown Mfn-2 mediator fusion, an evolutionarily conserved process responsible for surveillance homeostasis. Here, we find cardiac myocyte mitochondria lacking are pleiomorphic and have propensity to become enlarged. Consistent with underlying mild dysfunction, Mfn-2-deficient mice display modest hypertrophy accompanied by slight...

Background— The modification of proteins with O -linked β- N -acetylglucosamine ( -GlcNAc) represents a key posttranslational that modulates cellular function. Previous data suggest -GlcNAc may act as an intracellular metabolic or stress sensor, linking glucose metabolism to Considering this, we hypothesized augmentation levels endogenously recruitable mechanism cardioprotection. Methods and Results— In mouse hearts subjected in vivo ischemic preconditioning, were significantly elevated....

Rationale: At birth, there is a switch from placental to pulmonary circulation and the heart commences its aerobic metabolism. In cardiac myocytes, this transition marked by increased mitochondrial biogenesis remodeling of intracellular architecture. The mechanisms governing formation new mitochondria their expansion within myocytes remain largely unknown. Mitofusins (Mfn-1 Mfn-2) are known regulators networks, but role during perinatal maturation has yet be examined. Objective: objective...

Molecular studies examining the impact of mitochondrial morphology on mammalian heart have previously focused dynamin related protein-1 (Drp-1) and mitofusin-2 (Mfn-2), while role other mitofusin isoform, Mfn-1, has remained largely unexplored. In present study, we report generation initial characterization cardiomyocyte-specific Mfn-1 knockout (Mfn-1 KO) mice. Using electron microscopic analysis, detect a greater prevalence small, spherical mitochondria in KO hearts, indicating that absence...

The failing heart is subject to elevated metabolic demands, adverse remodeling, chronic apoptosis, and ventricular dysfunction. interplay among such pathologic changes largely unknown. Several laboratories have identified a unique posttranslational modification that may significant effects on cardiovascular function. O-linked β- N -acetylglucosamine (O-GlcNAc) (O-GlcNAcylation) integrates glucose metabolism with intracellular protein activity localization. Because O-GlcNAc derived from...

The outer mitochondrial membrane GTPase mitofusin 2 (Mfn2) is known to regulate endoplasmic reticulum (ER) shape in addition its fusion effects. However, role ER stress unknown. We report here that induction of with either thapsigargin or tunicamycin mouse embryonic fibroblasts leads up-regulation Mfn2 mRNA and protein levels no change the expression shaping factors Mfn1, Opa1, Drp1, Fis1. Genetic deletion but not Mfn1 cardiac myocytes mice led an increase chaperone proteins. ablation...

The regulation of cardiomyocyte hypertrophy is a complex interplay among many known and unknown processes. One specific pathway involves the phosphatase calcineurin, which regulates nuclear translocation essential cardiac transcription factor, factor activated T-cells (NFAT). Although metabolic dysregulation frequently described during hypertrophy, limited insights exist regarding various accessory pathways. metabolically derived signal, beta-O-linked N-acetylglucosamine (O-GlcNAc), has...

Metabolic signaling through the posttranslational linkage of N -acetylglucosamine ( O -GlcNAc) to cellular proteins represents a unique paradigm operative during lethal stress and pathway that we others have recently shown exert cytoprotective effects in vitro vivo. Accordingly, present work addresses contribution hexosaminidase responsible for removing -GlcNAc (ie, -GlcNAcase) from proteins. We used pharmacological inhibition, viral overexpression, RNA interference -GlcNAcase isolated...

We previously demonstrated that the O-linked beta-N-acetylglucosamine (O-GlcNAc) posttranslational modification confers cardioprotection at least partially through mitochondrial-dependent mechanisms, but it remained unclear if O-GlcNAc signaling interfered with other mechanisms of cell death. Because ischemia/hypoxia causes endoplasmic reticulum (ER) stress, we ascertained whether could attenuate ER stress-induced death per se. Before induction stress (with tunicamycin or brefeldin A),...

3,5-Seco-4-nor-cholestan-5-one oxime-3-ol (TRO40303) is a new cardioprotective compound coming from chemical series identified initially for neuroprotective properties. TRO40303 binds specifically to the mitochondrial translocator protein 18 kDa (TSPO) at cholesterol site. After intravenous administration, tissue distribution was comparable that of TSPO, and, in particular, drug accumulated rapidly heart. In model 35 min myocardial ischemia/24 h reperfusion rats, (2.5 mg/kg) reduced infarct...

We have shown that glycosylation of proteins with O ‐linked β‐N‐acetylglucosamine ( ‐GlcNAc) preserves mitochondrial membrane potential, attenuates post‐hypoxic injury, and reduces myocardial infarct size in vivo . Based on our recent identification voltage dependent anion channel (VDAC) as an ‐GlcNAc modified protein, we hypothesized signaling mediates cardioprotection by attenuating sensitivity to mPTP formation. Here, isolated cardiac mitochondria from Vehicle‐ (normal ‐GlcNAc), PUGNAc‐...

We recently reported that diabetic hearts have a paradoxical reduction in β‐ O ‐linked‐N‐acetylglucosamine ( ‐GlcNAc) signaling. Because enhancement of ‐GlcNAc signaling is cardioprotective, we hypothesized loss OGT activity sufficient to sensitize nondiabetic cardiac myocytes post‐hypoxic injury. Here, loxP‐ flanked neonatal mouse (n=3/group) were infected with an adenovirus carrying cre recombinase gene (AdCre, 72hours; 50 moi). Expression reduced expression (44+/−16%, p<0.05) and...

We have demonstrated that the post‐translational modification of O‐linked beta‐N‐acetylglucosamine (O‐GlcNAc) confers cardioprotection at least partially through mitochondrial dependent mechanisms. Because ischemia/hypoxia causes endoplasmic reticulum (ER) stress, we evaluated a potential link between O‐GlcNAc signaling and ER stress. pharmacologically induced stress to define these two processes. Normoxic induction (tunicamycin or brefeldin A) augmented in cardiomyocytes (p<0.05). Prior...

The peroxisome proliferator activated receptor gamma coactivator‐1alpha (PGC‐1α) is a transcriptional activator of many metabolic genes, especially those used in the metabolism fatty acids. Within failing heart, shift occurs from utilizing mainly acids to relying more on glycolysis. Concurrent with this reduction expression PGC‐1α and an increase glucose‐derived, post‐translational modification O‐GlcNAc. We hypothesized that O‐GlcNAc signaling would play role control during change. subjected...

Mitochondrial dysfunction figures prominently in post‐ischemic cardiac myocyte injury. A novel cytoprotective compound, TRO40303, can reduce infarct size following ischemia‐reperfusion injury mice and prevent contractile vitro . To better understand how TRO40303 potentially mediates such protection from oxidative damage seen injury, we induced stress neonatal rat myocytes (n>/=5/group) using hydrogen peroxide (100µmol/L) assessed changes intracellular calcium levels (via Rhod‐2AM...

The post-translational modification, O-linked β-N-acetylglucosamine (O-GlcNAc), is a metabolic and nutrient sensor which exerts cardioprotective effects. However, paucity of information exists regarding the direct regulation O-GlcNAc levels in heart. We evaluated role transferase (OGT, adds to proteins) on cardiac myocyte survival following hypoxia-reoxygentaion. infected isolated myocytes (n=4–5/group) with adenovirus carrying OGT gene (AdOGT), or treated an inhibitor (TT04), subjected them...

Hexosamine biosynthesis, an accessory pathway for glucose metabolism, culminates in the formation of UDP-GlcNAc, which is monosaccharide donor post-translational modification, O-linked beta-N-acetylglucosamine (O-GlcNAc). Augmented hexosamine biosynthesis has been implicated pathogenesis diabetes many peripheral tissues. Yet, transporters cardiac myocytes are predominantly insulin dependent, thereby limiting intracellular availability diabetic myocytes. Driven by such paradoxes, we...

We have recently found that hypoxia-reoxygenation reduces global levels of a cytoprotective metabolic signal (O-linked β-N-acetylglucosamine, i.e. O-GlcNAc). Such observations may indicate net increase in O-GlcNAcase (GCA, removes O-GlcNAc) activity. Because O-GlcNAc exerts protective effects on the myocardium, we hypothesized gene transfer GCA further and sensitizes cardiac myocytes to post-hypoxic injury. Isolated (n=4–5/group) were infected with adenovirus overexpressing (AdGCA), or...

We have recently discovered an endogenous mechanism of cytoprotection in the heart that involves post-translational modification proteins with a metabolic signal. Although this stress-responsive (beta-O linkage N-acetylglucosamine, i.e. O-GlcNAc) exerts profound salubrious effects on myocardium vivo, details regarding pathobiology cardiac myocyte remain unexplored. hypothesized O-GlcNAc levels decrease following hypoxia and manipulation these would affect survival. subjected isolated...