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Proteolytic System (proteolytic + system)

Distribution by Scientific Domains

Medical Sciences	60%
Life Sciences	26%

Selected Abstracts

Molecular mechanisms activating muscle protein degradation in chronic kidney disease and other catabolic conditions

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 3 2005
J. Du
Abstract Muscle atrophy is a prominent feature of chronic kidney disease (CKD) and is frequent in other catabolic conditions. Results from animal models of these conditions as well as patients indicate that atrophy is mainly owing to accelerated muscle proteolysis in the ubiquitin-proteasome (Ub-P'some) proteolytic system. The Ub-P'some system, however, rapidly degrades actin or myosin but cannot breakdown actomyosin or myofibrils. Consequently, another protease must initially cleave the complex structure of muscle. We identified caspase-3 as an initial and potentially rate-limiting proteolytic step that cleaves actomyosin/myofibrils to produce substrates degraded by the Ub-P'some system. In rodent models of CKD and other catabolic conditions, we find that caspase-3 is activated and cleaves actomyosin to actin, myosin and their fragments. This initial proteolytic step in muscle leaves a characteristic footprint, a 14-kDa actin band, providing a potential diagnostic tool to detect muscle catabolism. We also found that stimulation of caspase-3 activity depends on inhibition of IRS-1-associated phosphatidylinositol 3-kinase (PI3K) activity; inhibiting PI3K in muscle cells also leads to expression of a critical E3-ubiquitin-conjugating enzyme involved in muscle protein breakdown: atrogin-1/MAFbx. Thus, protein breakdown by caspase-3 and the ubiquitin-proteasome system in muscle are stimulated by the same signal: a low PI3K activity. These responses could yield therapeutic strategies to block muscle atrophy. [source]

The ubiquitin-proteasome system and its role in ethanol-induced disorders

ADDICTION BIOLOGY, Issue 1 2002
Terrence M. Donohue Jr
The levels of these proteins are controlled by their rates of degradation. Similarly, protein catabolism plays a crucial role in prolonging cellular life by destroying damaged proteins that are potentially cytotoxic. A major player in these catabolic reactions is the ubiquitin-proteasome system, a novel proteolytic system that has become the primary proteolytic pathway in eukaryotic cells. Ubiquitin-mediated proteolysis is now regarded as the major pathway by which most intracellular proteins are destroyed. Equally important, from a toxicological standpoint, is that the ubiquitin-proteasome system is also widely considered to be a cellular defense mechanism, since it is involved in the removal of damaged proteins generated by adduct formation and oxidative stress. This review describes the history and the components of the ubiquitin-proteasome system, its regulation and its role in pathological states, with the major emphasis on ethanol-induced organ injury. The available literature cited here deals mainly with the effects of ethanol consumption on the ubiquitin-proteasome pathway in the liver. However, since this proteolytic system is an essential pathway in all cells it is an attractive experimental model and therapeutic target in extrahepatic organs such as the brain and heart that are also affected by excessive alcohol consumption. [source]

Apoptosis-inhibiting activities of BIR family proteins in Xenopus egg extracts

FEBS JOURNAL, Issue 9 2005
Yuichi Tsuchiya
In many animal species including Xenopus, ovulated eggs possess an intrinsic apoptotic execution system. This program is inhibited for a limited time by some maternal apoptosis inhibitors, although their molecular properties remain uncharacterized. Baculovirus IAP repeat (BIR) family proteins contain evolutionarily conserved BIR domains and play important roles in apoptosis suppression, and are therefore good candidates as maternal apoptosis inhibitors. We identified four maternal BIR family proteins in Xenopus eggs and, using the biochemical advantages of egg extracts, examined their physiological functions. These molecules included two survivin-related proteins, xEIAP/XLX, and a possible ortholog of XIAP named xXIAP. The addition of recombinant xXIAP greatly delayed apoptotic execution, whereas the immunodepletion of endogenous xXIAP significantly accelerated the onset of apoptosis. In contrast, xEIAP/XLX was a poor apoptosis inhibitor, and neither of the survivin orthologs showed anti-apoptotic activity in our assay. Both xEIAP/XLX and xXIAP were degraded by activated caspases, and also by a novel proteolytic system that required the presence of C-terminal RING finger domain but was insensitive to proteasome inhibition. Our data suggest that the regulation of endogenous xXIAP concentration is important for the survival of Xenopus eggs. [source]

Assembly of cytochrome f into the cytochrome bf complex in isolated pea chloroplasts

FEBS JOURNAL, Issue 3 2001
Ruth M. Mould
Structural features of cytochrome f necessary for assembly into the cytochrome bf complex were examined in isolated pea chloroplasts following import of 35S-labelled chimeric precursor proteins, consisting of the presequence of the small subunit of Rubisco fused to the turnip cytochrome f precursor. Assembly was detected by nondenaturing gel electrophoresis of dodecyl maltoside-solubilized thylakoid membranes. A cytochrome f polypeptide unable to bind haem because of mutagenesis of Cys21 and Cys24 to alanine residues was assembled into the complex and had similar stability to the wild-type polypeptide. This indicates that covalent haem binding to cytochrome f is not necessary for assembly of the protein into the cytochrome bf complex. A truncated protein lacking the C-terminal 33 amino acid residues, including the transmembrane span and the stroma-exposed region, was translocated across the thylakoid membrane, had a similar stability to wild-type cytochrome f but was not assembled into the complex. This indicates that the C-terminal region of cytochrome f is important for assembly into the complex. A mutant cytochrome f unable to bind haem and lacking the C-terminal region was also translocated across the thylakoid membrane but was extremely labile, indicating that, in the absence of the C-terminal membrane anchor, haem-less cytochrome f is recognized by a thylakoid proteolytic system. [source]

Neurons bearing presenilins: weapons for defense or suicide?

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 4 2000
B.O. Popescu
Abstract Apoptotic machinery designed for cell's organized self-destruction involve different systems of proteases which cleave vital proteins and disassemble nuclear and cytoplasmic structures, committing the cell to death. The most studied apoptotic proteolytic system is the caspase family, but calpains and the proteasome could play important roles as well. Alzheimer's disease associated presenilins showed to be a substrate for such proteolytic systems, being processed early in several apoptotic models, and recent data suggest that alternative presenilin fragments could regulate cell survival. Mutations in genes encoding presenilins proved to sensitize neurons to apoptosis by different mechanisms e.g. increased caspase-3 activation, oxyradicals production and calcium signaling dysregulation. Here we review the data involving presenilins in apoptosis and discuss a possible role of presenilins in the regulation of apoptotic biochemical machinery. [source]

Functionality of lactic acid bacteria peptidase activities in the hydrolysis of gliadin-like fragments

LETTERS IN APPLIED MICROBIOLOGY, Issue 5 2008
C.L. Gerez
Abstract Aims:, To evaluate the role of the peptidase activities from sourdough lactic acid bacteria (LAB) in the degradation of ,-gliadin fragments. Methods and Results:, Different proline-containing substrates were hydrolysed by LAB indicating pro-specific peptidase activities. Lactobacillus plantarum CRL 775 and Pediococcus pentosaceus CRL 792 displayed the highest tri- and di-peptidase activities, respectively. Lactobacillus plantarum strains hydrolysed more than 60%,-gliadin fragments corresponding to the 31,43 and 62,75 amino acids in the protein after 2 h. None of the LAB strains alone could hydrolyse 57,89 ,-gliadin peptide; however, the combination of L. plantarum CRL 775 and P. pentosaceus CRL 792 led to hydrolysis (57%) of this peptide in 8 h. Conclusions:, The capacity of LAB strains to degrade ,-gliadin fragments was not correlated to individual peptidase activities. Several strains separately degraded the 31,43 and 62,75 ,-gliadin fragments, while the 57,89 peptide degradation was associated with the combination of peptidase profiles from pooled LAB strains. This is the first report on the peptide hydrolase system of sourdough pediococci and its ability to reduce ,-gliadin fragments. Significance and Impact of the Study:, This study contributes to a better knowledge of sourdough LAB proteolytic system and its role in the degradation of proline-rich ,-gliadin peptides involved in celiac disease. [source]

Systemic levels of plasmin,antiplasmin complexes are correlated with the expansion rate of small abdominal aortic aneurysms

BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 4 2001
J. S. Lindholt
Background: The cystatine proteolytic system, the serine proteolytic system and the metallodependent proteolytic system have all been reported to be involved in the matrix degradation of the aortic wall, causing abdominal aortic aneurysm (AAA). Plasmin is a common activator of all three systems and could theoretically be involved in the pathogenesis of AAA by activating all three systems. However, plasmin is immediately inactivated by antiplasmin, forming plasmin,antiplasmin (PAP) complexes when it reaches the circulation. This study was designed to assess whether the systemic levels of PAP complex in conservatively treated patients with AAA could be related to the natural history of AAA. Methods: In 1994, 112 of 141 men with AAA (greater than 3 cm) diagnosed by population screening were interviewed, examined, and had blood samples taken and prepared for serum and ethylenediamine tetra-acetic acid plasma by a standard method. The serum and plasma were frozen at , 21°C until analysis. Of the 112 patients, 99 were followed with annual control scans and blood pressure measurements for 1,5 (mean 2·5) years, and were referred for operation if the AAA exceeded 5 cm in diameter. Of the 99 patients, a random sample of 70 had their level of PAP complexes determined (Dade Behring, Rødovre, Denmark). Furthermore, the level of serum elastin peptides (SEPs) was determined by enzyme-linked immunosorbent assay. Spearman's rank sum correlation test, multivariate linear regression analysis and receiver,operator characteristic (ROC) curve analysis were used for statistical analysis (SPSS 10.0; SPSS, Chicago, Illinois, USA). Results: The level of PAP complex was positively correlated with annual expansion rate (r = 0·29, P = 0·01), but not with the initial AAA size (r = 0·17, P = 0·16) or SEP (r = 0·04, P = 0·77). The significant association to expansion persisted after adjustment for initial AAA size, SEP and smoking. Furthermore, the level of PAP complex was significantly predictive for AAAs expanding to operation recommendable size (area under ROC curve 65 per cent), with an optimal sensitivity and specificity of 65 and 67 per cent respectively. SEP level was also significantly predictive for AAAs expanding to operation recommendable size (area under ROC curve 56 per cent), with an optimal sensitivity and specificity of 56 and 57 per cent. Conclusion: The progression of AAA seems to be caused by a general activation of the proteolytic systems involving plasmin and not by genetic or environmental factors causing increased activation of specific proteases or decreased activity of their specific inhibitors. Furthermore, the level of PAP complex in patients with an aneurysm seems to have a better and independently predictive value of the natural history of AAA, compared with the best serological predictor known to date, the serum level of elastin peptides. © 2001 British Journal of Surgery Society Ltd [source]

The ubiquitin,proteosome proteolytic system.

CELL BIOCHEMISTRY AND FUNCTION, Issue 3 2004
From classical biochemistry to human diseases.
No abstract is available for this article. [source]

Neurons bearing presenilins: weapons for defense or suicide?

Chronic Ethanol Consumption Results in Atypical Liver Injury in Copper/Zinc Superoxide Dismutase Deficient Mice

ALCOHOLISM, Issue 2 2010
Tiana V. Curry-McCoy
Background:, Ethanol metabolism increases production of reactive oxygen species, including superoxide () in the liver, resulting in significant oxidative stress, which causes cellular damage. Superoxide dismutase (SOD) is an antioxidant enzyme that converts superoxide to less toxic intermediates, preventing accumulation. Because the absence of SOD would confer less resistance to oxidative stress, we determined whether damage to hepatic proteolytic systems was greater in SOD,/, than in SOD+/+ mice after chronic ethanol feeding. Methods:, Female wild-type (SOD+/+) and Cu/Zn-SOD knockout (SOD,/,) mice were pair-fed ethanol and control liquid diets for 24 days, after which liver injury was assessed. Results:, Ethanol-fed SOD,/, mice had 4-fold higher blood ethanol, 2.8-fold higher alanine aminotransferase levels, 20% higher liver weight, a 1.4-fold rise in hepatic protein levels, and 35 to 70% higher levels of lipid peroxides than corresponding wild-type mice. While wild-type mice exhibited fatty liver after ethanol administration, SOD,/, mice showed no evidence of ethanol-induced steatosis, although triglyceride levels were elevated in both groups of knockout mice. Ethanol administration caused no significant change in proteasome activity, but caused lysosomal leakage in livers of SOD,/, mice but not in wild-type mice. Alcohol dehydrogenase activity was reduced by 50 to 60% in ethanol-fed SOD,/, mice compared with all other groups. Additionally, while ethanol administration induced cytochrome P450 2E1 (CYP2E1) activity in wild-type mice, it caused no such induction in SOD,/, mice. Unexpectedly, ethanol feeding significantly elevated total and mitochondrial levels of glutathione in SOD knockout mice compared with wild-type mice. Conclusion:, Ethanol-fed SOD,/, mice exhibited lower alcohol dehydrogenase activity and lack of CYP2E1 inducibility, thereby causing decreased ethanol metabolism compared with wild-type mice. These and other atypical responses to ethanol, including the absence of ethanol-induced steatosis and enhanced glutathione levels, appear to be linked to enhanced oxidative stress due to lack of antioxidant enzyme capacity. [source]

The Role of Cytokines in Regulating Protein Metabolism and Muscle Function

NUTRITION REVIEWS, Issue 2 2002
Elena Zoico M.D.
Multiple lines of evidence suggest that cytokines influence different physiologic functions of skeletal muscle cells, including anabolic and catabolic processes and programmed cell death. Cytokines play an important role not only in muscle homeostasis, therefore, but also in the pathogenesis of different relevant clinical conditions characterized by alterations in protein metabolism. Recently discovered cytokines, such as ciliary neurotrophic factor and growth/differentiation factor-8, as well as the more studied tumor necrosis factor-,, interleukin-1, interleukin-6, and the interferons, have been implicated in the regulation of muscle protein turnover. Their postreceptor signaling pathways, proteolytic systems, and the mechanisms of protein synthesis inhibition involved in different catabolic conditions have been partially clarified. Moreover, recent studies have shown that cytokines can directly influence skeletal muscle contractility independent of changes in muscle protein content. Even though several gaps remain in our understanding, these observations may be useful in the development of strategies to control protein metabolism and muscle function in different clinical conditions. [source]

Systemic levels of plasmin,antiplasmin complexes are correlated with the expansion rate of small abdominal aortic aneurysms

2133: p62/sequestosome 1 as a regulator of proteasome inhibitor-induced autophagy in human retinal pigment epithelial cells

ACTA OPHTHALMOLOGICA, Issue 2010
K KAARNIRANTA
Purpose The pathogenesis of age-related macular degeneration involves impaired protein degradation in retinal pigment epithelial (RPE) cells. The ubiquitin-proteasome pathway and the lysosomal pathway including autophagy are the major proteolytic systems in eukaryotic cells. Prior to proteolysis, heat shock proteins (HSPs) attempt to refold stress ,induced misfolded proteins and thus prevent the accumulation of cytoplasmic protein aggregates. The functional roles of p62 and HSP70 were evaluated in conjunction with protesome inhibitor -induced autophagy in human RPE cells (ARPE-19). Methods The p62, HSP70 and ubiquitin protein levels and localization were analyzed by Western blotting and immunofluorescense. Confocal and transmission electron microscopy were used to detect cellular organelles and to evaluate the morphological changes. The p62 and HSP70 levels were modulated using RNA interference and overexpression techniques. Cell viability was measured by colorimetric assay. Results Proteasome inhibition evoked the accumulation of p62 and HSP70 that strongly co-localized with each other in perinuclear aggregates. The p62 accumulation was time and concentration dependent after MG-132 proteasome inhibitor loading. Interestingly, autophagy induction was p62 and Hsp70 independent. In addition, the p62 silencing decreased the ubiquitination level of the perinuclear aggregates. Recently we showed that hsp70 mRNA depletion increased cell death in ARPE-19 cells. Here we now demonstrate that p62 mRNA silencing has similar effects on cellular viability. Conclusion The p62 and HSP70 are central molecules in the regulation of protein turnover in human retinal pigment epithelial cells in proteasome inhibitor- induced autophagy. [source]

Cell death in lens epithelial cells after stimulation of the sigma-2 receptor

ACTA OPHTHALMOLOGICA, Issue 2009
JO KARLSSON
Purpose The aim was to investigate the mechanisms of cell death in lens epithelial cells after administration of siramesine, a sigma-2 receptor agonist. Methods Human lens epithelial cells in culture were exposed to siramesine and examined for morphological changes using DIC or calcein as a cytoplasmic marker. Lysosomes were studied using acridine orange and MagicRed. Proteolytic activity of the proteasome, calpain, caspases and cathepsins in living cells or cell extracts were studied using different fluorogenic substrates. Results Siramesine at low concentrations increased the cytoplasmic proteolytic activity of the proteasome and the calpain system. Early effects was also observed with respect to lysosomal morphology, acidity and function. Activation of caspase-3 and the appearance of nuclei with an apoptotic morphology were also found. Conclusion Siramesine at very low concentrations affects lens epithelial cells with perturbation of the major proteolytic systems, lysosomal morphology and results in caspase activation and cell death. Siramesine may be a promising substance for clinical studies concerning the treatment of PCO. [source]