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Updated: Aug 20, 2026

Imaging ATG9A, a Multi-Spanning Membrane Protein
Published on: June 16, 2023
Atg8 is essential for macropexophagy in Hansenula polymorpha
Iryna Monastyrska1, Meis van der Heide, Arjen M Krikken
1Eukaryotic Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, PO Box 14, 9750 AA Haren, the Netherlands.
Abstract:
We have isolated a peroxisome-degradation-deficient (pdd) mutant of the methylotrophic yeast Hansenula polymorpha via gene tagging mutagenesis. Sequencing revealed that the mutant was affected in the HpATG8 gene. HpAtg8 is a protein with high sequence similarity to both Pichia pastoris and Saccharomyces cerevisiae Atg8 and appeared to be essential for selective peroxisome degradation (macropexophagy) and nitrogen-limitation induced microautophagy. Fluorescence microscopy revealed that a GFP.Atg8 fusion protein was located close to the vacuole. After induction of macropexophagy, the GFP.Atg8 containing spot extended to engulf an individual peroxisome. In cells of a constructed deletion strain, sequestration of individual organelles was never completed; analysis of series of serial sections revealed that invariably a minor diaphragm-like opening remained. We hypothesize that H. polymorpha Atg8 facilitates sealing of the sequestering membranes during selective peroxisome degradation.
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