Search

Excessive ethanol ingestion can reduce skeletal muscle protein synthesis (MPS) through the disruption of signaling along the Akt-mTOR pathway and increase muscle protein degradation (MPD) through the Ubiquitin Proteasome Pathway (UPP) and autophagy. Identification of interventions that curb the disrupting effects of alcohol misuse on MPS and MPD are of central importance for the prevention of chronic health complications that arise from muscle loss. Physical activity is one potential strategy to combat the deleterious effects of alcohol on skeletal muscle. Therefore, the purpose of this study was to investigate the interaction between daily wheel running and binge-patterned ethanol consumption, through episodes of voluntary binge-patterned ethanol drinking, on signaling factors along the Akt-mTOR, Ubiquitin-Proteasome, and autophagy pathways. Adult female C57BL/6J mice received daily access to cages with or without running wheels for 2.5 h/day for five weeks. During the final five days of the study, mice received 2-4 h of daily access to sipper tubes containing water (n = 14 sedentary; n = 15 running) or 20% ethanol (n = 14 sedentary; n = 16 running) 30 min after running wheel access, using the "Drinking in the Dark" (DID) model of binge-patterned ethanol consumption. Immediately after the final episode of DID, gastrocnemius muscle was extracted. Western blotting was performed to measure proteins along Akt-mTOR, Ubiquitin-Proteasome, and autophagy pathways, and PCR was used to assess mRNA expression of atrogenes. Ethanol access increased expression of MAFbx by 82% (p = 0.048), but did not robustly influence Akt-mTOR or UPP signaling. Daily wheel access did not prevent alcohol-induced MAFbx expression; however, ethanol access decreased the phosphorylation of p70S6K by 45% in running mice (p = 0.020). These results suggest that physical activity may be insufficient to prevent alcohol-induced changes to signaling factors along pathways involved in muscle loss. Instead, binge-patterned ethanol ingestion may impair the benefits of physical activity on factors involved in MPS. [ABSTRACT FROM AUTHOR]

Multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare autosomal recessive metabolic disease. Patients present with metabolic decompensation, muscle weakness, respiratory failure, and cardiomyopathy. Late-onset MADD is primarily caused by mutations in the ETFDH gene. Here, we report a patient who has been diagnosed with Down syndrome after birth following karyotype analysis and simultaneously carrying compound heterozygous variants of ETFDH (c.3G > C (p. M1?); c.725C > T (p. T242I), which is novel). Further molecular analyses revealed that the novel c.725C > T (p. T242I) mutation enhances the degradation of electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) via the ubiquitin proteasome pathway. Five ubiquitin E3 ligases (STUB1, RNF40, UBE3C, CUL3, and CUL1) and one ubiquitin modification site (Cystein, C101) of the ETF-QO were reported in this study. Our study not only expanded the pathogenic variant spectrum of ETFDH gene but also proved that the c.725C > T (p. T242I) will promote protein degradation through ubiquitin proteasome pathway. [ABSTRACT FROM AUTHOR]

• Mutation of UCHL1's C152 lipid binding site alleviated TBI-induced cell death. • C152 mutation decreased ubiquitinated proteins, activation of autophagy after TBI. • C152 mutation decreased white and gray matter injury after TBI. • C152 mutation improved motor and cognitive function after TBI. Ubiquitin carboxy terminal hydrolase L1 (UCHL1) is a protein highly expressed in neurons that may play important roles in the ubiquitin proteasome pathway (UPP) in neurons, axonal integrity, and motor function after traumatic brain injury (TBI). Binding of reactive lipid species to cysteine 152 of UCHL1 results in unfolding, aggregation, and inactivation of the enzyme. To test the role of this mechanism in TBI, mice bearing a cysteine to alanine mutation at site 152 (C152A mice) that renders UCHL1 resistant to inactivation by reactive lipids were subjected to the controlled cortical impact model (CCI) of TBI and compared to wild type (WT) controls. Alterations in protein ubiquitination and activation of autophagy pathway markers in traumatized brain were detected by immunoblotting. Cell death and axonal injury were determined by histological assessment and anti-amyloid precursor protein (APP) immunohistochemistry. Behavioral outcomes were determined using the beam balance and Morris water maze tests. C152A mice had reduced accumulation of ubiquitinated proteins, decreased activation of the autophagy markers Beclin-1 and LC3B, a decreased number of abnormal axons, decreased CA1 cell death, and improved motor and cognitive function compared to WT controls after CCI; no significant change in spared tissue volume was observed. These results suggest that binding of lipid substrates to cysteine 152 of UCHL1 is important in the pathogenesis of injury and recovery after TBI and may be a novel target for future therapeutic approaches. [ABSTRACT FROM AUTHOR]

Stress is a common problem diminishing the muscle development of broilers. Creatine (Cr), an energy buffer in skeletal muscle, plays a fundamental role in muscle physiology. This study aimed to evaluate the effect of Cr monohydrate (CMH) on protein breakdown in chicken myotubes challenged by corticosterone (CORT) in vitro. The morphology of myotube was measured and the activation of ubiquitin proteasome (UP) pathway was determined. The result showed that CORT treatment decreased myotube diameter (P < 0.05), increased 3-methyl-histidine (3M-His) content in medium, enhanced the mRNA expression levels of muscle ring finger1 (MuRF1) and Atrogin1 (P < 0.001), and Atrogin1 protein level (P < 0.05) compared with control. By contrast, CMH increased myotube diameter (P < 0.05) and myosin heavy chain (MHC) expression (P < 0.001), whereas decreased 3M-His and the mRNA and protein levels of Atrogin1 (P < 0.05), compared to control. In the present of CMH, the decreased myotube diameter and increased 3M-His, mRNA levels of MuRF1 and Atrogin1 , and Atrogin1 protein level by CORT were partially relieved (P < 0.05). Hence, the result suggests that CMH alleviates CORT-induced protein breakdown by suppressing Atrogin1 expression in chicken myotubes. The result highlights the potential application of CMH in regulating muscle protein catabolism in chickens under stress. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the effects of electrical stimulation by using rectangular and sine waveforms in the prevention of deep muscle atrophy in rat calf muscles. Rats were randomly divided into the following groups: control, hindlimb unloading (HU), and HU plus electrical stimulation (ES). The animals in the ES group were electrically stimulated using rectangular waveform (RS) on the left calves and sine waveform (SS) on the right calves, twice a day, for 2 weeks during unloading. HU for 2 weeks resulted in a loss of the muscle mass, a decrease in the cross-sectional area of the muscle fibers, and overexpression of ubiquitinated proteins in the gastrocnemius and soleus muscles. In contrast, electrical stimulation with RS attenuated the HU-induced reduction in the cross-sectional area of muscle fibers and the increase of ubiquitinated proteins in the gastrocnemius muscle. However, electrical stimulation with RS failed to prevent muscle atrophy in the deep portion of the gastrocnemius and the soleus muscles. Nevertheless, electrical stimulation with SS attenuated the HU-induced muscle atrophy and the up-regulation of ubiquitinated proteins in both gastrocnemius and soleus muscles. This indicates that SS was more effective in the prevention of deep muscle atrophy than RS. Since the skin muscle layers act like the plates of a capacitor, separated by the subcutaneous adipose layer, the SS can pass through this capacitor more easily than the RS. Hence, SS can prevent the progressive loss of muscle fibers in the deep portion of the calf muscles. [ABSTRACT FROM AUTHOR]

Abstract: Muscle growth is determined primarily by the balance between protein synthesis and degradation. When rates of protein synthesis are similar between individuals, protein degradation is critical in explaining differences in growth efficiency. Studies in mammals showed that muscle atrophy results from increased protein breakdown, and is associated with activation of the ubiquitin proteasome pathway, including induction of the muscle-specific ubiquitin protein ligase, MuRF1. Animals lacking MuRF1 are resistant to muscle atrophy. In fish, little is known about the role of the proteasome/MuRF pathway in muscle degradation. The objectives of this study were to: 1) clone and characterize MuRF genes in rainbow trout; and 2) determine expression of MuRF genes in association with starvation- and vitellogenesis-induced muscle atrophy in rainbow trout. We have identified full-length cDNA sequences for three MuRF genes (MuRF1, MuRF2, and MuRF3). These genes encode proteins with typical MuRF structural domains, including a RING-finger, a B-box and a Leucine-rich coiled-coil domain. RT-PCR analysis showed that MuRF genes are predominantly expressed in muscle and heart tissues. Real time PCR analysis revealed that expression of all MuRF genes is up-regulated during starvation and MuRF3 is up-regulated in vitellogenesis-associated muscle degradation. These results suggest that MuRF genes have an important role in fish muscle protein degradation. Further studies are warranted to assess the potential use of MuRF genes as tools to monitor fish muscle growth and degradation. [Copyright &y& Elsevier]

Abstract: It is clear that components of the proteasome and the ubiquitin proteasome pathway play a direct mechanistic role in the regulation of a variety of DNA repair processes. Intriguingly, a wealth of evidence suggests that this is also the case during the regulation of gene transcription. Here we review our current understanding of how the ubiquitin proteasome pathway influences nucleotide excision repair, and discuss how studies that investigate the role of this pathway in the regulation of gene transcription might also contribute to our mechanistic understanding of its role in DNA repair. [Copyright &y& Elsevier]

Abstract: The proteasome is a multi-catalytic proteinase complex that is integral to intracellular proteolysis, and plays a key role in many critical functions. Inhibition of the proteasome induces cell cycle arrest and apoptosis in a variety of tumor cell types in vitro and in vivo, thus making it an attractive therapeutic agent for the treatment of cancer. Bortezomib (VELCADE®; formerly PS-341) is the first proteasome inhibitor to enter into clinical practice. Phases I–III clinical trials have shown bortezomib and proteasome inhibition to be well tolerated. Impressive anti-tumor activity against relapsed and refractory multiple myeloma has been seen, leading to the approval of bortezomib for this indication, where it seems poised to change the natural history of the disease. Additional studies are ongoing to define its role in initial therapy of myeloma, as well as in other areas, such as non-Hodgkin''s lymphoma. While bortezomib has displayed less activity as a single agent against solid tumors, new research into combination regimens with other chemotherapeutics holds promise to increase efficacy against both solid tumors and hematologic malignancies. Heat shock proteins (HSPs) are molecular chaperones that interact with the ubiquitin-proteasome pathway, and function to aid in de novo protein folding and to stabilize key intracellular signaling proteins. Many tumors overexpress high-affinity HSPs that form unusually stable interactions with oncogenic client proteins, while normal, adjacent tissues only exhibit a latent, low-affinity form. Phase I/II clinical trials are ongoing with two potent HSP-90 inhibitors, which have so far been well tolerated in patients with some activity in hematologic malignancies. Drugs that modulate protein turnover through the proteasome, and protein folding through HSPs, seem destined to form an important part of our therapeutic armamentarium against a variety of malignancies. [Copyright &y& Elsevier]

Abstract: Aging-related alterations of the ubiquitin proteasome pathway (UPP) have been reported in locomotor skeletal muscle. Specifically, declines in proteasome activity have been observed in the soleus of senescent animals compared to the soleus of young controls. However, the influence of aging on the mRNA levels of key components within the ubiquitin conjugation cascade (UCC) remains unknown. We hypothesized that aged soleus muscle would exhibit downregulated expression of select UCC mRNA and decreased levels of ubiquitin–protein conjugates. To test this postulate, we harvested soleus muscles from 6 and 24–26 month old Fisher 344 rats. Aging resulted in a decline in mRNA expression of two key UCC components in soleus muscle; ubiquitin conjugating enzyme E214k (E214k) and muscle ring finger-1 (MuRF1). Surprisingly, no age-related differences existed in the total content of endogenous ubiquitin–protein conjugates in the soleus muscle. Nonetheless, a selective decrease in the level of ubiquitin–protein conjugates (∼30kDa) was detected in the soleus of senescent animals. These results indicate that the soleus muscle displays a differential mRNA response of select UCC components to aging. Furthermore, the decline in E214k and MuRF1 mRNA levels may contribute to altered substrate degradation by the UCC in the soleus muscle of senescent rats. [Copyright &y& Elsevier]

Proteolysis-targeting chimera (PROTAC) could selectively degrade target protein and may become a promising strategy for treating estrogen receptor α (ERα) positive breast cancers. Here, we designed penetrated peptide-based PROTACs by constructing an N-terminal lactam cyclic to improve proteolytic stability and cell penetration. We used a lactam cyclic peptide as ERα binding ligand, 6-aminocaproic acid as a linker, and a hydroxylated pentapeptide structure for recruiting E3 ligase to obtain heterobifunctional compounds. The resulting optimized compound I-6 selectively recruited ERα to the E3 ligase complex for promoting the degradation of ERα. Compound I-6 possessed strong effect on MCF-7 cell toxicity (IC 50 ∼9.7 μM) and significantly enhanced activities in inducing ERα degradation. Meanwhile, I-6 performed much stronger potency in inhibition of tumors growth than tamoxifen. This work is a successful template to construct PROTACs based on cell-permeable peptides, which could extend the chemical space of PROTACs. Image 1 • Synthesis of cell-permeable peptide-based PROTACs targeting estrogen receptor α. • I-6 possessed strong effect on ERα positive cells MCF-7 toxicity (IC 50 ∼9.7 μM). • I-6 exhibited membrane penetrability and pro-apoptosis activity and tumor growth inhibitory activities in vivo. • I-6 selectively recruited ERα to the VHL E3 ligase complex, leading to the degradation of ERα in a proteasome-dependent manner. • All results indicated PROTAC I-6 may be a promising candidate which extends the breast cancer therapy. [ABSTRACT FROM AUTHOR]