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Research Paper
A Peroxisomal Lon Protease and Peroxisome Degradation by Autophagy Play Key Roles in Vitality of Hansenula polymorpha Cells
Eda Bener Aksam, Anne Koek, Stefanie Jourdan, Marten Veenhuis and Ida J. van der Klei
volume 3 | issue 2
March/April 2007Pages: 96 - 105
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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 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.
Authors
Eda Bener Aksam
University of Groningen
Anne Koek
University of Groningen
Stefanie Jourdan
University of Groningen
Marten Veenhuis
University of Groningen
Ida J. van der Klei
University of Groningen
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.