Diabetic Cardiomyopathy: Role of the E3 Ubiquitin Ligase (original) (raw)
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Cardiac proteasome functional insufficiency plays a pathogenic role in diabetic cardiomyopathy
Journal of molecular and cellular cardiology, 2016
Diabetic cardiomyopathy is a major risk factor in diabetic patients but its pathogenesis remains poorly understood. The ubiquitin-proteasome system (UPS) facilitates protein quality control by degrading unnecessary and damaged proteins in eukaryotic cells, and dysfunction of UPS is implicated in various cardiac diseases. However, the overall functional status of the UPS and its pathophysiological role in diabetic cardiomyopathy have not been determined. Type I diabetes was induced in wild-type and transgenic mice expressing a UPS functional reporter (GFPdgn) by injections of streptozotocin (STZ). STZ-induced diabetes progressively impaired cardiac UPS function as evidenced by the accumulation of GFPdgn proteins beginning two weeks after diabetes induction, and by a buildup of total and lysine (K) 48-linked polyubiquitinated proteins in the heart. To examine the functional role of the UPS in diabetic cardiomyopathy, cardiac overexpression of PA28α (PA28αOE) was used to enhance protea...
The Ubiquitin-Proteasome Proteolytic Pathway in Heart vs Skeletal Muscle: Effects of Acute Diabetes
Biochemical and Biophysical Research Communications, 2000
The ubiquitin-proteasome system is thought to play a major role in normal muscle protein turnover and to contribute to diabetes-induced protein wasting in skeletal muscle. However, its importance in cardiac muscle is not clear. We measured heart muscle mRNA for ubiquitin and for the C2 and C8 proteasomal subunits, the amount of free ubiquitin and the proteasome chymotrypsin-like proteolytic activity in control and diabetic rats. Results were compared to those in skeletal muscle (rectus). Heart ubiquitin, C2 and C8 subunit mRNA and proteolytic activity were significantly greater than in skeletal muscle (P < 0.05). This suggests that the ubiquitin proteasomal pathway may also be important for normal heart muscle turnover. Diabetes increased ubiquitin mRNA by ϳ50% in heart (P < 0.03) and by ϳ100% in skeletal muscle (P < 0.005). It remained high after 3 days of insulin treatment in both tissues. C2 and C8 subunit mRNA did not change with diabetes or insulin treatment. Diabetes did not change the amount of free ubiquitin or the proteasomal (lactacystin-inhibitable) chymotrypsin-like peptidase activity in heart or skeletal muscle. In conclusions, gene expression for several components of the ubiquitin-proteasome proteolytic pathway is significantly higher in cardiac than in skeletal muscle, as is the proteasome chymotrypsin-like peptidase activity. Diabetes increases the expression of ubiquitin but not C2 or C8 subunit mRNA, nor does it significantly alter the amount of free ubiquitin or the proteasome chymotrypsin-like peptidase activity. The ratelimiting step of enhanced protein degradation in diabetic rat heart and skeletal muscle may be located at ubiquitin conjugation and/or its binding to proteasome, not at the ubiquitin availability or the proteasome itself.
Ubiquitin-proteasome system and hereditary cardiomyopathies
Journal of Molecular and Cellular Cardiology, 2014
Adequate protein turnover is essential for cardiac homeostasis. Different protein quality controls are involved in the maintenance of protein homeostasis, including molecular chaperones and co-chaperones, the autophagy-lysosomal pathway, and the ubiquitin-proteasome system (UPS). In the last decade, a series of evidence has underlined a major function of the UPS in cardiac physiology and disease. Particularly, recent studies have shown that dysfunctional proteasomal function leads to cardiac disorders. Hypertrophic and dilated cardiomyopathies are the two most prevalent inherited cardiomyopathies. Both are primarily transmitted as an autosomal-dominant trait and mainly caused by mutations in genes encoding components of the cardiac sarcomere, including a relevant striated muscle-specific E3 ubiquitin ligase. A growing body of evidence indicates impairment of the UPS in inherited cardiomyopathies as determined by measurement of the level of ubiquitinated proteins, the activities of the proteasome and/or the use of fluorescent UPS reporter substrates. The present review will propose mechanisms of UPS impairment in inherited cardiomyopathies, summarize the potential consequences of UPS impairment, including activation of the unfolded protein response, and underline some therapeutic options available to restore proteasome function and therefore cardiac homeostasis and function. This article is part of a Special Issue entitled "Protein Quality Control, the Ubiquitin Proteasome System, and Autophagy".
Cardiovascular Diabetology, 2007
We have reviewed the impact of the ubiquitin proteasome system (UPS) on atherosclerosis progression of diabetic patients. A puzzle of many pieces of evidence suggests that UPS, in addition to its role in the removal of damaged proteins, is involved in a number of biological processes including inflammation, proliferation and apoptosis, all of which constitute important characteristics of atherosclerosis. From what can be gathered from the very few studies on the UPS in diabetic cardiovascular diseases published so far, the system seems to be functionally active to a different extent in the initiation, progression, and complication stage of atherosclerosis in the diabetic people. Further evidence for this theory, however, has to be given, for instance by specifically targeted antagonism of the UPS. Nonetheless, this hypothesis may help us understand why diverse therapeutic interventions, which have in common the ability to reduce ubiquitin-proteasome activity, can impede or delay the onset of diabetes and cardiovascular diseases (CVD).
Is insulin signaling molecules misguided in diabetes for ubiquitin–proteasome mediated degradation?
Molecular and Cellular Biochemistry, 2005
Recent mining of the human and mouse genomes, use of yeast genetics, and detailed analyses of several biochemical pathways, have resulted in the identification of many new roles for ubiquitin-proteasome mediated degradation of proteins. In the context of last year's award of Noble Prize (Chemistry) work, the ubiquitin and ubiquitin-like modifications are increasingly recognized as key regulatory events in health and disease. Although the ATP-dependent ubiquitin-proteasome system has evolved as premier cellular proteolytic machinery, dysregulation of this system by several different mechanisms leads to inappropriate degradation of specific proteins and pathological consequences. While aberrations in the ubiquitin-proteasome pathway have been implicated in certain malignancies and neurodegenerative disorders, recent studies indicate a role for this system in the pathogenesis of diabetes and its complications. Inappropriate degradation of insulin signaling molecules such as insulin receptor substrates (IRS-1 and IRS-2) has been demonstrated in experimental diabetes, mediated in part through the up-regulation of suppressors of cytokine signaling (SOCS). It appears that altered ubiquitin-proteasome system might be one of the molecular mechanisms of insulin resistance in many pathological situations. Drugs that modulate the SOCS action and/or proteasomal degradation of proteins could become novel agents for the treatment of insulin resistance and Type 2 diabetes. (Mol Cell Biochem 275: 117-125, 2005)
The Ubiquitin Proteasome System in Ischemic and Dilated Cardiomyopathy
International Journal of Molecular Sciences
Dilated (DCM) and ischemic cardiomyopathies (ICM) are associated with cardiac remodeling, where the ubiquitin–proteasome system (UPS) holds a central role. Little is known about the UPS and its alterations in patients suffering from DCM or ICM. The aim of this study is to characterize the UPS activity in human heart tissue from cardiomyopathy patients. Myocardial tissue from ICM (n = 23), DCM (n = 28), and control (n = 14) patients were used to quantify ubiquitinylated proteins, E3-ubiquitin-ligases muscle-atrophy-F-box (MAFbx)/atrogin-1, muscle-RING-finger-1 (MuRF1), and eukaryotic-translation-initiation-factor-4E (eIF4E), by Western blot. Furthermore, the proteasomal chymotrypsin-like and trypsin-like peptidase activities were determined fluorometrically. Enzyme activity of NAD(P)H oxidase was assessed as an index of reactive oxygen species production. The chymotrypsin- (p = 0.71) and caspase-like proteasomal activity (p = 0.93) was similar between the groups. Trypsin-like proteas...
Cardiovascular Pathology, 2009
Background: Because the ubiquitin-proteasome pathway Q1 (UPS) is required for activation of nuclear factor kappa beta (NFkB), a 16 transcription factor that regulates inflammatory genes, we evaluated the UPS activity, NFkB activation, and tumor necrosis factor-alpha 17 (TNF-alpha), a proinflammatory cytokine, in ischemic specimens of diabetic myocardium and relate them to the glycemic control (HbA 1c ), 18 oxidative stress (nitrotyrosine, a modified amino acid produced by reactive O 2 ), and cardiac outcome (echocardiographic parameters).
Functional Significance of the E3 Ubiquitin Ligases in Disease and Therapeutics
Hydrolases, 2021
E3 ubiquitin ligases of which there are >600 putative in humans, constitute a family of highly heterogeneous proteins and protein complexes that are the ultimate enzymes responsible for the recruitment of an ubiquitin loaded E2 ubiquitin-conjugating enzyme, recognise the appropriate protein substrate and directly or indirectly transfer the ubiquitin load onto the substrate. The aftermath of an E3 ligase activity is usually the formation of an isopeptide bond between the free carboxylate group of ubiquitin’s C-terminal Gly76 and an ε-amino group of the substrate’s Lys, even though non-canonical ubiquitylation on non-amine groups of target proteins have been observed. E3 ligases are grouped into four distinct families: HECT, RING-finger/U-box, RBR and PHD-finger. E3 ubiquitin ligases play critical roles in subcellular signalling cascades in eukaryotes. Dysfunctional E3 ubiquitin ligases therefore tend to inflict dramatic effects on human health and may result in the development of ...
Ubiquitin Proteasome Dysfunction in Human Hypertrophic and Dilated Cardiomyopathies
Circulation, 2010
Background-The ubiquitin proteasome system maintains a dynamic equilibrium of proteins and prevents accumulation of damaged and misfolded proteins, yet its role in human cardiac dysfunction is not well understood. The present study evaluated ubiquitin proteasome system function in human heart failure and hypertrophic cardiomyopathy (HCM). Methods and Results-Proteasome function was studied in human nonfailing donor hearts, explanted failing hearts, and myectomy samples from patients with HCM. Proteasome proteolytic activities were markedly reduced in failing and HCM hearts compared with nonfailing hearts (PϽ0.01). This activity was partially restored after mechanical unloading in failing hearts (PϽ0.01) and was significantly lower in HCM hearts with pathogenic sarcomere mutations than in those lacking these mutations (PϽ0.05). There were no changes in the protein content of ubiquitin proteasome system subunits (ie, 11S, 20S, and 19S) or in active-site labeling of the 20S proteolytic subunit -5 among groups to explain decreased ubiquitin proteasome system activity in HCM and failing hearts. Examination of protein oxidation revealed that total protein carbonyls, 4-hydroxynonenylated proteins, and oxidative modification to 19S ATPase subunit Rpt 5 were increased in failing compared with nonfailing hearts. Conclusions-Proteasome activity in HCM and failing human hearts is impaired in the absence of changes in proteasome protein content or availability of proteolytic active sites. These data provide strong evidence that posttranslational modifications to the proteasome may account for defective protein degradation in human cardiomyopathies. (Circulation. 2010;121:997-1004.) The online-only Data Supplement is available with this article at http://circ.ahajournals.org/cgi/content/full/CIRCULATIONAHA.109.904557/DC1.