المؤلفون: Bjørn Grinde, Per Ottar Seglen

المصدر: Biochimica et Biophysica Acta (BBA) - General Subjects. 676:43-50

مصطلحات موضوعية: Male, Stereochemistry, Glutamine, Phenylalanine, Biophysics, Biology, Protein degradation, Biochemistry, Structure-Activity Relationship, Leucine, Autophagy, Animals, Histidine, Asparagine, Amino Acids, Molecular Biology, chemistry.chemical_classification, Tryptophan, Proteins, Photo-reactive amino acid analog, Rats, Amino acid, Liver, chemistry

الوصف: Analogues and derivatives of six of the amino acids which most effectively inhibit protein degradation in isolated rat hepatocytes (leucine, asparagine, glutamine, histidine, phenylalanine and tryptophan) were investigated to see if they could antagonize or mimic the effect of the parent compound. No antagonists were found. Amino alcohols and amino acid amides tended to inhibit protein degradation strongly, apparently by a direct lysosomotropic effect as indicated by their ability to cause lysosomal vacuolation. Amino acid alkyl esters and dipeptides inhibited degradation to approximately the same extent as did their parent amino acids, possibly by being converted to free amino acids intracellularly. Of several leucine analogues tested, four (L-norleucine, L-norvaline, D-norleucine and L-allo-isoleucine) were found to be as effective as leucine in inhibiting protein degradation. None of the analogues had any effect on protein synthesis. Since leucine appears to play a unique role as a regulator of bulk autophagy in hepatocytes, the availability of active leucine agonists may help tj elucidate the biochemical mechanism for control of this important process.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4ad0b925eef389ee278b49cac7dc7ad0Test
https://doi.org/10.1016/0304-4165Test(81)90007-6

المؤلفون: Paul B. Gordon, Per Ottar Seglen

المصدر: Archives of Biochemistry and Biophysics. 217:282-294

مصطلحات موضوعية: Male, Adenosine, Biophysics, Endogeny, Puromycin Aminonucleoside, Biology, Protein degradation, Biochemistry, chemistry.chemical_compound, Adenosine Triphosphate, medicine, Protein biosynthesis, Animals, Purine metabolism, Molecular Biology, chemistry.chemical_classification, Dose-Response Relationship, Drug, Mercaptopurine, Adenine, Autophagy, Proteins, Rats, Inbred Strains, Riboside, Rats, Amino acid, Liver, chemistry, Purines, Lysosomes, medicine.drug

الوصف: About 100 different purine derivatives and analogs were tested for their effect on protein synthesis and protein degradation in isolated rat hepatocytes. These included 6-aminopurines (adenine and adenosine analogs), 6-mercaptopurines, chloropurines, oxypurines, cytokinins, methylxanthines, methylindoles, benzimidazoles, and benzodiazepines. Most of the compounds were either inactive or inhibited protein synthesis as much as or more than they inhibited protein degradation. However, three methylated 6-aminopurines (3-methyladenine, 6-dimethylaminopurine riboside, and puromycin aminonucleoside) and four 6-mercaptopurines (6-methylmercaptopurine, 6-methylmercaptopurine riboside, 6-mercaptopurine riboside, and 2′,3′,5t - triacetyl-6-mercaptopurine riboside) had a markedly stronger effect on protein degradation than on synthesis, and might therefore be potentially useful as selective degradation inhibitors. None of the seven above-mentioned purines had any significant effect on the degradation of the exogenous protein, asialofetuin, and would therefore seem to selectively inhibit endogenous protein degradation. Since the degradation was not further affected by purines in the presence of amino acids or lysosomotropic amines, it is suggested that the purines exert their effect specifically upon the autophagic/lysosomal pathway. All the mercaptopurines significantly depressed cellular ATP levels, whereas the methylated aminopurines did not. For this reason, the latter are probably more useful as degradation inhibitors. 3-Methyladenine had no effect on protein synthesis at a concentration (5 m m ) which inhibited protein degradation by more than 60%, and may therefore be regarded as a highly specific inhibitor of autophagy.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::cbb3d1d32cf246940c91647e9d840220Test
https://doi.org/10.1016/0003-9861Test(82)90504-5

المؤلفون: P. B. Gordon, Per Ottar Seglen

مصطلحات موضوعية: Purine, Liver cytology, Protein degradation, Biology, chemistry.chemical_compound, Adenosine Triphosphate, Phagocytosis, Protein biosynthesis, Animals, Amino Acids, Biological Sciences: Cell Biology, Cells, Cultured, chemistry.chemical_classification, Multidisciplinary, Adenine, Autophagy, Proteins, Cell biology, Amino acid, Rats, Biochemistry, chemistry, Liver, Protein Biosynthesis, Autolysis, Lysosomes, Adenosine triphosphate, Intracellular

الوصف: 3-Methyladenine (5 mM) inhibits endogenous protein degradation in isolated rat hepatocytes by about 60%, while having no adverse effect on the degradation of an exogenous protein (asialofetuin), on protein synthesis, or on intracellular ATP levels. 3-Methyladenine appears to act specifically upon the autophagic/lysosomal pathway of degradation, as judged from its lack of effect in the presence of amino acids or a lysosomotropic amine (propylamine). The effect of the purine is not mediated by amino acids because the inhibition of protein degradation is accompanied by a significant depression of intracellular amino acid levels. The ability of 3-methyladenine to suppress the formation of electron microscopically visible autophagosomes suggests that it may be regarded as a specific inhibitor of autophagy.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::ce1babbf577c2810d389d0036c16cd81Test
https://europepmc.org/articles/PMC346086Test/

المؤلفون: Per Ottar Seglen, Atilla L. Kovács, Katalin Molnár

المصدر: FEBS letters. 134(2)

مصطلحات موضوعية: Male, Adenosine, Biophysics, Endogeny, Biology, Protein degradation, Puromycin Aminonucleoside, Biochemistry, chemistry.chemical_compound, Phagocytosis, Structural Biology, Genetics, medicine, Autophagy, Animals, Purine metabolism, Molecular Biology, chemistry.chemical_classification, Proteins, Rats, Inbred Strains, Cell Biology, Riboside, Amino acid, Rats, Mechanism of action, chemistry, Liver, Vacuoles, Puromycin, medicine.symptom, Lysosomes, medicine.drug

الوصف: Some methylated adenosine derivatives, most notably 6-dimethylaminopurine riboside and puromycin aminonucleoside, have been shown to inhibit the autophagic/lysosomal pathway of endogenous protein degradation in isolated rat hepatocytes [ 11. The mechanism of action of these methylaminopurines is not known. One possibility is that they might exert their effect by preventing the first reaction in the autophagic sequence, i.e., the sequestration of cytoplasmic material into autophagosomes [2], as do the amino acids [3-61. Another possibility is that the purines might interfere with the further processing of the autophagosomes, including their fusion with lysosomes, as seems to be the case with most other degradation inhibitors [7]. To distinguish between these two possibilities, we have undertaken a correlated biochemical and morphometric analysis of the effects of several adenine and adenosine derivatives. The results indicate that the methylated aminopurines inhibit endogenous protein degradation at the level of autophagic sequestration.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::5036a22588df243803779a6b2a5e944fTest
https://pubmed.ncbi.nlm.nih.gov/7308488Test

المؤلفون: Paul B. Gordon, Per Ottar Seglen, Alessandro Poli

المصدر: Biochimica et biophysica acta. 630(1)

مصطلحات موضوعية: Male, Glutamine, Biophysics, Protein degradation, Biology, Biochemistry, Phagocytosis, Valine, Autophagy, Animals, Asparagine, Tyrosine, Amino Acids, Molecular Biology, Amino acid synthesis, Transaminases, chemistry.chemical_classification, Aminooxyacetic Acid, Proteins, Drug Synergism, Amino acid, Rats, chemistry, Liver, Leucine, Lysosomes

الوصف: Protein degradation in isolated rat hepatocytes, as measured by the release of [ 14 C]valine from pre-labelled protein, is partly inhibited by a physiologically balanced mixture of amino acids. The inhibition is largely due to the seven amino acids leucine, phenylalanine, tyrosine, tryptophan, histidine, asparagine and glutamine. When the amino acids are tested individually at different concentrations, asparagine and glutamine are the strongest inhibitors. However, when various combinations are tested, a mixture of the first five amino acids as well as a combination of leucine and asparagine inhibit protein degradation particularly strongly. The inhibition brought about by asparagine plus leucine is not additive to the inhibition by propylamine, a lysosomotropic inhibitor; thus indicating that the amino acids act exclusively upon the lysosomal pathway of protein degradation. Following a lag of about 15 min the effect of asparagine plus leucine is maximal and equal to the effect of propylamine, suggesting that their inhibition of the lysosomal pathway is complete as well as specific. Degradation of endocytosed 125 I-labelled asialofetuin is not affected by asparagine plus leucine, indicating that the amino acids do not affect lysosomes directly, but rather inhibit autophagy at a step prior to the fusion of autophagic vacuoles with lysosomes. The aminotransferase inhibitor, aminooxyacetate, does not prevent the inhibitory effect of any of the amino acids, i.e. amino acid metabolites are apparently not involved.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::f844900be2290b6389d63f36f8f12687Test
https://pubmed.ncbi.nlm.nih.gov/7388042Test

المؤلفون: Attila L. Kovács, Per Ottar Seglen, Albrecht Reith

المصدر: Experimental cell research. 137(1)

مصطلحات موضوعية: Male, Leupeptins, Motility, Stimulation, Biology, Protein degradation, In Vitro Techniques, Vinblastine, chemistry.chemical_compound, Phagocytosis, medicine, Autophagy, Animals, chemistry.chemical_classification, Propylamines, Leupeptin, Proteins, Rats, Inbred Strains, Cell Biology, Cell biology, Amino acid, Rats, Organoids, Kinetics, Microscopy, Electron, Mechanism of action, chemistry, Biochemistry, Liver, Vacuoles, medicine.symptom, Oligopeptides, medicine.drug

الوصف: Vinblastine, leupeptin and propylamine (a lysosomotropic weak base) inhibit intracellular protein degradation by different mechanisms (impairment of microtubular function, inhibition of lysosomal proteases, and elevation of lysosomal pH, respectively). In isolated rat hepatocytes, a paradoxical accumulation of autophagosomes was seen after treatment with each of the inhibitors at concentrations which inhibited protein degradation strongly. Such accumulation might occur if formation of autophagosomes proceeded at a normal rate, while their subsequent processing (e.g. their fusion with lysosomes) were inhibited. Vinblastine could conceivably reduce the motility of both autophagosomes and lysosomes, thereby preventing contact between them, whereas leupeptin and propylamine might reduce the ability of lysosomes to fuse by causing lysosomal constipation and neutralization/swelling, respectively. Amino acids also inhibited hepatocytic protein degradation, but in contrast to the other inhibitors (and regardless of the presence of the latter) they caused a decrease rather than an increase in the contents of autophagosomes, in accordance with their accepted mechanism of action as primary inhibitors of autophagy. It is proposed that drug-induced accumulation of autophagosomes in most cases may be due to the inhibition of late steps in the autophagic/lysosomal pathway rather than to a stimulation of autophagy.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::288c0b58c28b77cd31b83a372b539ffaTest
https://pubmed.ncbi.nlm.nih.gov/7056284Test