A peroxisomal lon protease and peroxisome degradation by autophagy play key roles in vitality of Hansenula polymorpha cells.
In eukaryote cells various mechanisms exist that are responsible for the removal of non-functional proteins. Here we show that in the yeast Hansenula polymorpha (H. polymorpha) a peroxisomal Lon protease, Pln, plays a role in degradation of unfolded and non-assembled peroxisomal matrix proteins. In addition, we demonstrate that whole peroxisomes are constitutively degraded by autophagy during normal vegetative growth of WT cells. Deletion of both H. polymorpha PLN and ATG1, required for autophagy, resulted in a significant increase in peroxisome numbers, paralleled by a decrease in cell viability relative to WT cells. Also, in these cells and in cells of PLN and ATG1 single deletion strains, the intracellular levels of reactive oxygen species had increased relative to WT controls. The enhanced generation of reactive oxygen species may be related to an uneven distribution of peroxisomal catalase activities in the mutant cells, as demonstrated by cytochemistry. We speculate that in the absence of HpPln or autophagy unfolded and non-assembled peroxisomal matrix proteins accumulate, which can form aggregates and lead to an imbalance in hydrogen peroxide production and degradation in some of the organelles.
Aksam
Eda Bener
EB
Eukaryotic Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, Haren, The Netherlands.
Koek
Anne
A
Kiel
Jan A K W
JA
Jourdan
Stefanie
S
Veenhuis
Marten
M
van der Klei
Ida J
IJ
D001343:Autophagy / Q000502:physiology*; D002374:Catalase / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D020675:Peroxisomes / Q000201:enzymology* / Q000648:ultrastructure; D010802:Phylogeny; D010843:Pichia / Q000166:cytology* / Q000201:enzymology* / Q000254:growth & development / Q000648:ultrastructure; D049070:Protease La / Q000737:chemistry / Q000378:metabolism*; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D017382:Reactive Oxygen Species / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012995:Solubility
D005656:Fungal Proteins; D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins; D002374:Catalase; D049070:Protease La