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Modification of a ubiquitin-like protein Paz2 conducted micropexophagy through formation of a novel membrane

Hiroyuki Mukaiyama1, Misuzu Baba, Masako Osumi

  • 1Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto 606-8502, Japan.

Molecular Biology of the Cell
|September 19, 2003
PubMed

Insights

Microautophagy utilizes a novel membrane structure and a modified protein, Paz2-I, to degrade peroxisomes. This process highlights shared machinery between microautophagy and macroautophagy.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Yeast Genetics

Background:

  • Microautophagy involves direct sequestration of cytosolic components by vacuolar/lysosomal membranes for degradation.
  • Emerging evidence suggests overlap in molecular machinery between microautophagy and macroautophagy.
  • The precise mechanisms of microautophagy, particularly de novo membrane formation, remain largely undefined.

Purpose of the Study:

  • To elucidate the molecular mechanisms underlying micropexophagy in Pichia pastoris.
  • To investigate the role of the ubiquitin-like protein Paz2 and its modification in microautophagy.
  • To identify novel structures involved in peroxisome sequestration during micropexophagy.

Main Methods:

  • Genetic analysis in Pichia pastoris.
  • Protein modification assays to characterize Paz2.
  • Microscopy to identify and analyze novel membrane structures.

Main Results:

  • Identified a modified form of Paz2 (Paz2-I) generated by Paz8 and Gsa7, analogous to Aut7 lipidation in macroautophagy.
  • Discovered a novel membrane structure essential for peroxisome sequestration during micropexophagy.
  • Demonstrated that the Paz2 modification system is required for the assembly of this membrane structure and Paz2 localization.

Conclusions:

  • Paz2 and its modification system are crucial for micropexophagy via de novo membrane formation.
  • This study reveals a convergence point between microautophagy and macroautophagy concerning membrane biogenesis.
  • The findings provide a mechanistic explanation for the shared molecular machinery between these degradation pathways.

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