Organelle autophagy in yeast

PhD ceremony: Ms. V. Todde, 11.00 uur, Doopsgezinde Kerk, Oude Boteringestraat 33, Groningen

Dissertation: Organelle autophagy in yeast

Promotor(s): prof. I.J. van der Klei

Faculty: Mathematics and Natural Sciences

Organelles (e.g. peroxisomes, vacuoles etc) biogenesis and degradation (autophagy) is finely regulated. In this thesis we study different modes of organelle autophagy in yeast cells and the role of certain autophagic proteins. In Chapter 1 is presented an overview ofautophagy-related human diseases. In Chapter 2 we have shown: 1) that the peroxine Pex14p has no role in microautophagy; 2) the phosphorylation state of Pex14 may represent a signalling machinery for peroxisome degradation; 3) minor amounts of Pex14p are required for macropexophagy. In Chapter 3 Is shown that HpAtg19-like protein is not involved in peroxisome autophagy. In Chapter 4 We observed a dual location of S. cerevisiae Atg22 on the vacuole and peroxisome membranes without functions in peroxisomal biogenesis or autophagy. Chapter 5 describes the details of the autophagy phenotype of an S. cerevisiae atg22 mutant: 1) autophagic vesicles accumulates in the vacuole of nitrogen starved cells; 2) is a microautophagic phenotype; 3) is unrelated to leucine; 4) is showed a novel phenotype in oleate media (unrelated to leucine) similar for vacuolar lipase mutant atg15 and not to the protease pep4. Probably, the phenotype is related to malfunction in lipid degradation of microautophagic vesicles maybe related to a reduced vacuolar lipase activity in atg22 cells and possibly due to the accumulation of lipids. Chapter 6 describes a novel mode of lipid body (LB) degradation in vacuoles of S. cerevisiae cells via microautophagy. This process occurs and is stimulated in oleic acid growing cells independent by general autophagy.