المؤلفون: Per E. Stromhaug, Trond Berg, Kristian Berg, Per Ottar Seglen

المصدر: The Biochemical journal. 321

مصطلحات موضوعية: Male, Radiation-Sensitizing Agents, Porphyrins, Endosome, Biochemistry, chemistry.chemical_compound, Cytosol, In vivo, Lactate dehydrogenase, Phagosomes, Animals, Rats, Wistar, Molecular Biology, chemistry.chemical_classification, biology, Leupeptin, Autophagy, Acid phosphatase, Cell Biology, Rats, Enzyme, chemistry, Liver, biology.protein, Lysosomes, Subcellular Fractions, Research Article

الوصف: A photoactivatable porphyrin, tetra(4-sulphonatophenyl)porphine (TPPS4), was shown to accumulate in rat hepatocytes as a linear function of dose after intravenous injection, and to localize predominantly in hepatocytic lysosomes. A major fraction of the lysosomal enzymes acid phosphatase and N-acetyl-β-d-glucosaminidase was inactivated by TPPS4 after 20 h of contact with the drug in vivo in the absence of photoactivation. On exposure of isolated hepatocytes to light, photoactivated TPPS4 caused additional inactivation of the lysosomal enzymes as well as inactivation of intralysosomal lactate dehydrogenase (LDH), a cytosolic enzyme that accumulated in lysosomes as a result of autophagy during a 2 h incubation of hepatocytes at 37 °C in the dark (in the presence of the proteinase inhibitor leupeptin to prevent degradation of intralysosomal LDH). Photoactivation of TPPS4 also induced lysosomal rupture, with a loss of lysosomal enzymes, autophagocytosed LDH, endocytosed 125I-tyramine-cellobiose-asialo-orosomucoid and TPPS4 from the lysosomes. However, LDH-containing autophagosomes, accumulated in the presence of vinblastine (a microtubule inhibitor used to prevent the fusion of lysosomes with autophagosomes or endosomes), were not affected by TPPS4. TPPS4 may thus be useful as a selective lysosomal (or endosomal) perturbant in the study of autophagic–endocytic–lysosomal interactions.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::1cdec3921b82f8902d0f2be55b1d2fd7Test
https://pubmed.ncbi.nlm.nih.gov/9003422Test

المؤلفون: Amy C. Munthe-Kaas, Mary Ann S. Dybedal, Per Ottar Seglen

المصدر: Experimental Cell Research. 155:121-128

مصطلحات موضوعية: Leupeptins, Proteolysis, Chronic lymphocytic leukemia, Lymphocyte, Endogeny, Protein degradation, Biology, chemistry.chemical_compound, Phagocytosis, Autophagy, medicine, Humans, Lymphocytes, Amino Acids, chemistry.chemical_classification, Propylamines, medicine.diagnostic_test, Adenine, Leupeptin, Proteins, Cell Biology, medicine.disease, Leukemia, Lymphoid, Neoplasm Proteins, Amino acid, medicine.anatomical_structure, chemistry, Biochemistry, Cytoplasm, Lysosomes

الوصف: Lymphocytes from normal human subjects and from patients with chronic lymphocytic leukemia were found to degrade their endogenous protein at similar rates (2.5–3.0%/h) when incubated in an amino acid-free buffer. Protein degradation was inhibited 20–35 % by inhibitors of autophagic sequestration (amino acids, 3-methyladenine) and by inhibitors of intra-lysosomal proteolysis (leupeptin, propylamine), the extent of inhibition being similar in normal and leukemic lymphocytes. The inhibitor effects, together with the electronmicroscopic demonstration of autophagosomes in the lymphocyte cytoplasm, is taken as evidence for the existence of an autophagic-lysosomal pathway in human lymphocytes, potentially responsible for as much as one-third of their overall protein degradation.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::dc496afd1eb90b5bb6fc506dc9d3968eTest
https://doi.org/10.1016/0014-4827Test(84)90773-0

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: 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: 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