Temperature dependence of protein degradation, autophagic sequestration and mitochondrial sugar uptake in rat hepatocytes.
Lysosomal (propylamine-sensitive) protein degradation as well as the energy-dependent (chymostatin-sensitive) part of the non-lysosomal protein degradation was found to be strongly affected by temperature in isolated rat hepatocytes, the activation energy (Ea) being about 25 kcal/mol for both processes. In contrast, the energy-independent (chymostatin-resistant) part of the non-lysosomal degradation had an Ea of approx. 10 kcal/mol only. Sequestration of electroinjected [14C]sucrose into sedimentable organelles showed a pronounced temperature dependence. By means of digitonin extraction it was possible to distinguish between a moderately temperature-sensitive mitochondrial sugar uptake (Ea approx. 12 kcal/mol) and a strongly temperature-dependent autophagic sequestration (Ea approx. 22 kcal/mol). There was no significant autophagic sequestration below 20 degrees C. The sequestration process is more temperature-sensitive than, for example, the early steps of endocytosis, and is likely to represent the major controlling step in the overall autophagic-lysosomal pathway.
D000818:Animals; D001343:Autophagy; D001693:Biological Transport, Active; D050260:Carbohydrate Metabolism; D004734:Energy Metabolism; D008099:Liver / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D011437:Propylamines / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D013696:Temperature
D009842:Oligopeptides; D011437:Propylamines; D011506:Proteins; C002101:chymostatin