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: Paul B. Gordon, Per Ottar Seglen

المصدر: Biochemical and biophysical research communications. 151(1)

مصطلحات موضوعية: Male, Endocytic cycle, Biophysics, Lactose, Vacuole, Biology, Vinblastine, Biochemistry, chemistry.chemical_compound, Phagocytosis, Autophagy, Animals, Asparagine, Molecular Biology, Cells, Cultured, chemistry.chemical_classification, Rats, Inbred Strains, Cell Biology, Compartment (chemistry), beta-Galactosidase, Endocytosis, Cell biology, Rats, Cytosol, Enzyme, chemistry, Liver, Vacuoles, Lysosomes

الوصف: [14C]Lactose, electroinjected into the cytosol of isolated rat hepatocytes, was sequestered by autophagy, transferred to lysosomes and eventually hydrolysed. Asparagine prevented the fusion between prelysosomal autophagic vacuoles and lysosomes, and caused lactose to accumulate in the former. However, if the hepatocytes were simultaneously allowed to endocytose added β-galactosidase, no lactose accumulation occurred. These results suggest that autophagically sequestered lactose and endocytosed β-galactosidase were delivered to the same prelysosomal vacuole, where the lactose was hydrolysed by the enzyme. The name amphisome is suggested for this new functional compartment, common to the autophagic and endocytic pathways.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::a5669d65cf3dfb38c3cff5f8e20b7dedTest
https://pubmed.ncbi.nlm.nih.gov/3126737Test

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