Altered ubiquitin-proteasome signaling in right ventricular hypertrophy and failure

Alterations in the ubiquitin-proteasome system (UPS) have been described in left ventricular hypertrophy and failure, although results have been inconsistent. The role of the UPS in right ventricular (RV) hypertrophy (RVH) and RV failure (RVF) is unknown. Given the greater percent increase in RV mass associated with RV afterload stress, as present in many congenital heart lesions, we hypothesized that alterations in the UPS could play an important role in RVH/RVF. UPS expression and activity were measured in the RV from mice with RVH/RVF secondary to pulmonary artery constriction (PAC). Epoxomicin and MG132 were used to inhibit the proteasome, and overexpression of the 11S PA28α subunit was used to activate the proteasome. PAC mice developed RVH (109.3% increase in RV weight to body weight), RV dilation with septal shift, RV dysfunction, and clinical RVF. Proteasomal function (26S β5 chymotrypsin-like activity) was decreased 26% ( P < 0.05). Protein expression of 19S subunit Rpt5 ( P < 0.05), UCHL1 deubiquitinase ( P < 0.0001), and Smurf1 E3 ubiquitin ligase ( P < 0.01) were increased, as were polyubiquitinated proteins ( P < 0.05) and free-ubiquitins ( P = 0.05). Pro-apoptotic Bax was increased ( P < 0.0001), whereas anti-apoptotic Bcl-2 decreased ( P < 0.05), resulting in a sixfold increase in the Bax/Bcl-2 ratio. Proteasomal inhibition did not accelerate RVF. However, proteasome enhancement by cardiac-specific proteasome overexpression partially improved survival. Proteasome activity is decreased in RVH/RVF, associated with upregulation of key UPS regulators and pro-apoptotic signaling. Enhancement of proteasome function partially attenuates RVF, suggesting that UPS dysfunction contributes to RVF.

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p97 Negatively Regulates NRF2 by Extracting Ubiquitylated NRF2 from the KEAP1-CUL3 E3 Complex

Molecular and Cellular Biology ◽

10.1128/mcb.00660-16 ◽

2017 ◽

Vol 37 (8) ◽

Cited By ~ 36

Author(s):

Shasha Tao ◽

Pengfei Liu ◽

Gang Luo ◽

Montserrat Rojo de la Vega ◽

Heping Chen ◽

...

Keyword(s):

Ubiquitin Ligase ◽

Protein Complexes ◽

E3 Ubiquitin Ligase ◽

Ubiquitin Proteasome System ◽

Proteasomal Degradation ◽

Ubiquitin Ligase Complex ◽

Ubiquitin Proteasome ◽

Client Proteins

ABSTRACT Activation of the stress-responsive transcription factor NRF2 is the major line of defense to combat oxidative or electrophilic insults. Under basal conditions, NRF2 is continuously ubiquitylated by the KEAP1-CUL3-RBX1 E3 ubiquitin ligase complex and is targeted to the proteasome for degradation (the canonical mechanism). However, the path from the CUL3 complex to ultimate proteasomal degradation was previously unknown. p97 is a ubiquitin-targeted ATP-dependent segregase that extracts ubiquitylated client proteins from membranes, protein complexes, or chromatin and has an essential role in autophagy and the ubiquitin proteasome system (UPS). In this study, we show that p97 negatively regulates NRF2 through the canonical pathway by extracting ubiquitylated NRF2 from the KEAP1-CUL3 E3 complex, with the aid of the heterodimeric cofactor UFD1/NPL4 and the UBA-UBX-containing protein UBXN7, for efficient proteasomal degradation. Given the role of NRF2 in chemoresistance and the surging interest in p97 inhibitors to treat cancers, our results indicate that dual p97/NRF2 inhibitors may offer a more potent and long-term avenue of p97-targeted treatment.

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Abstract 5417: Inducible 20S β Subunit LMP-2 is Down-Regulated in db/db Mouse Hearts with Diabetic Cardiomyopathy

Circulation ◽

10.1161/circ.118.suppl_18.s_546-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Lingyun Zu ◽

Djahida Bedja ◽

Lewis C Becker ◽

Zheqing P Cai

Keyword(s):

Diabetic Cardiomyopathy ◽

Ubiquitin Proteasome System ◽

Left Ventricular ◽

Heart Weight ◽

20S Proteasome ◽

Cardiac Atrophy ◽

Ubiquitin Proteasome ◽

And Control ◽

Fractional Shortening

Background: The ubiquitin-proteasome system (UPS) plays an important role in cell growth, differentiation, and survival. Low molecular mass polypeptide (LMP)-2 is an inducible 20S beta subunit and its role in diabetic cardiomyopathy has not been previously studied. We investigated the hypothesis that LMP-2 is down-regulated in diabetic hearts and is involved in diabetic cardiomyopathy. Methods: db/db mice and control db/+ littermates were studied at 20 weeks of age. Cardiac function was measured by echocardiography. Chymotryptic-like activity of the 20S proteasome was analyzed by fluorogenic assay using the substrate Suc-LLVY-aminomethycoumarin (-AMC). Results: db/db mice had a severe increase in blood glucose and a decrease in heart weight compared with db/+ mice (135±6 vs. 168±7 mg, n = 4, p < 0.01). Left ventricular function was decreased with a lower fractional shortening in db/db mice (48.7±3.2 vs. 60.7±0.4 %, n = 4, p < 0.05). LMP-2 was constitutively expressed in both db/+ and db/db mouse hearts, but its level was severely depressed in the db/db hearts (78±11 vs. 245±18 AU, n = 4, p < 0.01). Consistent with the change in LMP-2, chymotryptic-like activity was also significantly down-regulated in these diabetic hearts (3286±112 vs. 3598±52 AU, n = 3, p < 0.05). Furthermore, the role of LMP-2 in regulating 20S proteasome function and cardiac mass was determined in LMP-2 knockout and wildtype mice. Chymotryptic-like activity was significantly decreased in LMP-2 knockout mouse hearts (11156±360 vs. 18280±454 AU, n = 4, p < 0.01), and cardiac atrophy was found in these knockout mice (147±7.1 vs 178±10.5 mg, n=10; p < 0.01). Taken together, these results suggest that LMP-2 is necessary for normal proteasome function in the heart and its down-regulation may contribute to the development of diabetic cardiomyopathy.

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Diabetic cardiomyopathy: role of the E3 ubiquitin ligase

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00467.2015 ◽

2016 ◽

Vol 310 (7) ◽

pp. E473-E483 ◽

Cited By ~ 7

Author(s):

Tao Bai ◽

Fan Wang ◽

Nicholas Mellen ◽

Yang Zheng ◽

Lu Cai

Keyword(s):

Insulin Receptor ◽

Ubiquitin Ligase ◽

Diabetic Cardiomyopathy ◽

Ubiquitin Proteasome System ◽

Insulin Metabolism ◽

Insulin Receptor Substrates ◽

Ubiquitin Proteasome ◽

Novel Strategy ◽

New Strategies

Diabetic cardiomyopathy (DCM) is the leading cause of mortality in diabetes. As the number of cases of diabetes continues to rise, it is urgent to develop new strategies to protect against DCM, which is characterized by cardiac hypertrophy, increased apoptosis, fibrosis, and altered insulin metabolism. The E3 ubiquitin ligases (E3s), one component of the ubiquitin-proteasome system, play vital roles in all of the features of DCM listed above. They also modulate the activity of several transcription factors involved in the pathogenesis of DCM. In addition, the E3s degrade both insulin receptor and insulin receptor substrates and also regulate insulin gene transcription, leading to insulin resistance and insulin deficiency. Therefore, the E3s may be a driving force for DCM. This review summarizes currently available studies to analyze the roles of the E3s in DCM, enriches our knowledge of how DCM develops, and provides a novel strategy to protect heart from diabetes.

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Dynamic microRNA expression during the transition from right ventricular hypertrophy to failure

Physiological Genomics ◽

10.1152/physiolgenomics.00163.2011 ◽

2012 ◽

Vol 44 (10) ◽

pp. 562-575 ◽

Cited By ~ 68

Author(s):

Sushma Reddy ◽

Mingming Zhao ◽

Dong-Qing Hu ◽

Giovanni Fajardo ◽

Shijun Hu ◽

...

Keyword(s):

Heart Failure ◽

Right Ventricular ◽

Ventricular Hypertrophy ◽

Target Genes ◽

Left Ventricular ◽

Right Ventricular Hypertrophy ◽

Critical Question ◽

Regulatory Pathways ◽

Small Noncoding Rnas ◽

Pulmonary Artery Constriction

MicroRNAs (miRs) are small, noncoding RNAs that are emerging as crucial regulators of cardiac remodeling in left ventricular hypertrophy (LVH) and failure (LVF). However, there are no data on their role in right ventricular hypertrophy (RVH) and failure (RVF). This is a critical question given that the RV is uniquely at risk in patients with congenital right-sided obstructive lesions and in those with systemic RVs. We have developed a murine model of RVH and RVF using pulmonary artery constriction (PAC). miR microarray analysis of RV from PAC vs. control demonstrates altered miR expression with gene targets associated with cardiomyocyte survival and growth during hypertrophy (miR 199a-3p) and reactivation of the fetal gene program during heart failure (miR-208b). The transition from hypertrophy to heart failure is characterized by apoptosis and fibrosis (miRs-34, 21, 1). Most are similar to LVH/LVF. However, there are several key differences between RV and LV: four miRs (34a, 28, 148a, and 93) were upregulated in RVH/RVF that are downregulated or unchanged in LVH/LVF. Furthermore, there is a corresponding downregulation of their putative target genes involving cell survival, proliferation, metabolism, extracellular matrix turnover, and impaired proteosomal function. The current study demonstrates, for the first time, alterations in miRs during the process of RV remodeling and the gene regulatory pathways leading to RVH and RVF. Many of these alterations are similar to those in the afterload-stressed LV. miRs differentially regulated between the RV and LV may contribute to the RVs increased susceptibility to heart failure.

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Interaction of Gcn4 with target gene chromatin is modulated by proteasome function

Molecular Biology of the Cell ◽

10.1091/mbc.e16-03-0192 ◽

2016 ◽

Vol 27 (17) ◽

pp. 2735-2741 ◽

Cited By ~ 4

Author(s):

Gregory C. Howard ◽

William P. Tansey

Keyword(s):

Ubiquitin Ligase ◽

Target Gene ◽

Target Genes ◽

Proteasome Inhibition ◽

Ubiquitin Proteasome System ◽

Activation Of Transcription ◽

Ubiquitin Proteasome ◽

Promoter Occupancy ◽

Per Se

The ubiquitin–proteasome system (UPS) influences gene transcription in multiple ways. One way in which the UPS affects transcription centers on transcriptional activators, the function of which can be stimulated by components of the UPS that also trigger their destruction. Activation of transcription by the yeast activator Gcn4, for example, is attenuated by mutations in the ubiquitin ligase that mediates Gcn4 ubiquitylation or by inhibition of the proteasome, leading to the idea that ubiquitin-mediated proteolysis of Gcn4 is required for its activity. Here we probe the steps in Gcn4 activity that are perturbed by disruption of the UPS. We show that the ubiquitylation machinery and the proteasome control different steps in Gcn4 function and that proteasome activity is required for the ability of Gcn4 to bind to its target genes in the context of chromatin. Curiously, the effect of proteasome inhibition on Gcn4 activity is suppressed by mutations in the ubiquitin-selective chaperone Cdc48, revealing that proteolysis per se is not required for Gcn4 activity. Our data highlight the role of Cdc48 in controlling promoter occupancy by Gcn4 and support a model in which ubiquitylation of activators—not their destruction—is important for function.

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