1. Nitrogen Starvation and Stationary Phase Lipophagy Have Distinct Molecular Mechanisms
- Author
-
Muhammad Arifur Rahman, Taras Y. Nazarko, and Ravinder Kumar
- Subjects
autophagy ,Nitrogen ,lipid droplets ,Mutant ,Prl1 ,Vacuole fusion ,Vacuole ,yeast ,Models, Biological ,Catalysis ,Article ,S Phase ,lcsh:Chemistry ,Inorganic Chemistry ,Fungal Proteins ,03 medical and health sciences ,0302 clinical medicine ,Pichia pastoris ,Lipid droplet ,lipophagy ,Physical and Theoretical Chemistry ,lcsh:QH301-705.5 ,Molecular Biology ,Spectroscopy ,030304 developmental biology ,Komagataella phaffii ,2. Zero hunger ,selective autophagy ,0303 health sciences ,vacuole ,Chemistry ,Organic Chemistry ,Autophagy ,General Medicine ,Yeast ,Computer Science Applications ,Cell biology ,autophagic machinery ,Phenotype ,lcsh:Biology (General) ,lcsh:QD1-999 ,Cytoplasm ,Mutation ,Saccharomycetales ,Vacuoles ,030217 neurology & neurosurgery ,Intracellular - Abstract
In yeast, the selective autophagy of intracellular lipid droplets (LDs) or lipophagy can be induced by either nitrogen (N) starvation or carbon limitation (e.g. in the stationary (S) phase). We developed the yeast, Komagataella phaffii (formerly Pichia pastoris), as a new lipophagy model and compared the N-starvation and S-phase lipophagy in over 30 autophagy-related mutants using the Erg6-GFP processing assay. Surprisingly, two lipophagy pathways had hardly overlapping stringent molecular requirements. While the N-starvation lipophagy strictly depended on the core autophagic machinery (Atg1-Atg9, Atg18 and Vps15), vacuole fusion machinery (Vam7 and Ypt7) and vacuolar proteolysis (proteinases A and B), only Atg6 and proteinases A and B were essential for the S-phase lipophagy. The rest of the proteins were only partially required in the S-phase. Moreover, we isolated the prl1 (for positive regulator of lipophagy 1) mutant affected in the S-phase lipophagy but not N-starvation lipophagy. The prl1 defect was at a stage of delivery of the LDs from the cytoplasm to the vacuole further supporting mechanistically different nature of the two lipophagy pathways. Taken together, our results suggest that N-starvation and S-phase lipophagy have distinct molecular mechanisms.
- Published
- 2020