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Vac8 Controls Vacuolar Membrane Dynamics during Different Autophagy Pathways in Saccharomyces cerevisiae

Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, 44780 Bochum, Germany
Biomedizinische Forschung, Leibniz-Institute for Analytical Sciences (ISAS e.V.), 44139 Dortmund, Germany
Author to whom correspondence should be addressed.
Cells 2019, 8(7), 661;
Received: 4 May 2019 / Revised: 21 June 2019 / Accepted: 28 June 2019 / Published: 30 June 2019
(This article belongs to the Section Autophagy)
The yeast vacuole is a vital organelle, which is required for the degradation of aberrant intracellular or extracellular substrates and the recycling of the resulting nutrients as newly available building blocks for the cellular metabolism. Like the plant vacuole or the mammalian lysosome, the yeast vacuole is the destination of biosynthetic trafficking pathways that transport the vacuolar enzymes required for its functions. Moreover, substrates destined for degradation, like extracellular endocytosed cargoes that are transported by endosomes/multivesicular bodies as well as intracellular substrates that are transported via different forms of autophagosomes, have the vacuole as destination. We found that non-selective bulk autophagy of cytosolic proteins as well as the selective autophagic degradation of peroxisomes (pexophagy) and ribosomes (ribophagy) was dependent on the armadillo repeat protein Vac8 in Saccharomyces cerevisiae. Moreover, we showed that pexophagy and ribophagy depended on the palmitoylation of Vac8. In contrast, we described that Vac8 was not involved in the acidification of the vacuole nor in the targeting and maturation of certain biosynthetic cargoes, like the aspartyl-protease Pep4 (PrA) and the carboxy-peptidase Y (CPY), indicating a role of Vac8 in the uptake of selected cargoes. In addition, we found that the hallmark phenotype of the vac8Δ strain, namely the characteristic appearance of fragmented and clustered vacuoles, depended on the growth conditions. This fusion defect observed in standard glucose medium can be complemented by the replacement with oleic acid or glycerol medium. This complementation of vacuolar morphology also partially restores the degradation of peroxisomes. In summary, we found that Vac8 controlled vacuolar morphology and activity in a context- and cargo-dependent manner. View Full-Text
Keywords: autophagy; pexophagy; ribophagy; bulk autophagy; vacuole; Vac8 autophagy; pexophagy; ribophagy; bulk autophagy; vacuole; Vac8
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Boutouja, F.; Stiehm, C.M.; Reidick, C.; Mastalski, T.; Brinkmeier, R.; El Magraoui, F.; Platta, H.W. Vac8 Controls Vacuolar Membrane Dynamics during Different Autophagy Pathways in Saccharomyces cerevisiae. Cells 2019, 8, 661.

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