A peroxisomal lon protease and peroxisome degradation by autophagy play key roles in vitality of Hansenula polymorpha cells

Eda Bener Aksam, Anne Koek, Jan A.K.W. Kiel, Stefanie Jourdan, Marten Veenhuis, Ida J. van der Klei

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Abstract

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.
Original languageEnglish
Pages (from-to)96 - 105
Number of pages10
JournalAutophagy
Volume3
Issue number2
Publication statusPublished - 2007

Keywords

  • peroxisome
  • autophagy
  • lon protease
  • yeast
  • housekeeping
  • ALCOHOL OXIDASE
  • DIHYDROXYACETONE SYNTHASE
  • MOLECULAR CHAPERONES
  • MEMBRANE-PROTEINS
  • METHANOL OXIDASE
  • QUALITY-CONTROL
  • PIM1 PROTEASE
  • AAA PROTEASES
  • MITOCHONDRIA
  • GENE

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