Import into and degradation of cytosolic proteins by isolated yeast vacuoles.
In eukaryotic cells, both lysosomal and nonlysosomal pathways are involved in degradation of cytosolic proteins. The physiological condition of the cell often determines the degradation pathway of a specific protein. In this article, we show that cytosolic proteins can be taken up and degraded by isolated Saccharomyces cerevisiae vacuoles. After starvation of the cells, protein uptake increases. Uptake and degradation are temperature dependent and show biphasic kinetics. Vacuolar protein import is dependent on cytosolic heat shock proteins of the hsp70 family and on protease-sensitive component(s) on the outer surface of vacuoles. Degradation of the imported cytosolic proteins depends on a functional vacuolar ATPase. We show that the cytosolic isoform of yeast glyceraldehyde-3-phosphate dehydrogenase is degraded via this pathway. This import and degradation pathway is reminiscent of the protein transport pathway from the cytosol to lysosomes of mammalian cells.
Horst
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Zentrum für Biochemie und Molekulare Zellbiologie, Abteilung Biochemie 2, Georg-August Universität Göttingen, D-37073 Göttingen, Germany. Horst@uni-bc2.gwdg.de
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D001692:Biological Transport; D015415:Biomarkers; D003600:Cytosol / Q000378:metabolism* / Q000648:ultrastructure; D010450:Endopeptidases / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008854:Microscopy, Electron; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D013696:Temperature; D014617:Vacuoles / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure
D015415:Biomarkers; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D007527:Isoenzymes; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D010450:Endopeptidases; D006180:Proton-Translocating ATPases