Hansenula polymorpha Vam7p is required for macropexophagy

Patricia Stevens, Iryna Monastyrska, Adriana N. Leão-Helder, Ida J. van der Klei, Marten Veenhuis, Jan A.K.W. Kiel, [No Value] Monastyrska

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Abstract

We have analyzed the functions of two vacuolar t-SNAREs, Vam3p and Vam7p, in peroxisome degradation in the methylotrophic yeast Hansenula polymorpha. A Hp-vam7 mutant was strongly affected in peroxisome degradation by selective macropexophagy as well as non-selective microautophagy. Deletion of Hp-Vam3p function had only a minor effect on peroxisome degradation processes. Both proteins were located at the vacuolar membrane, with Hp-Vam7p also having a partially cytosolic location. Previously, in baker's yeast Vam3p and Vam7p have been demonstrated to be components of a t-SNARE complex essential for vacuole biogenesis. We speculate that the function of this complex in macropexophagy includes a role in membrane fusion processes between the outer membrane layer of sequestered peroxisomes and the vacuolar membrane. Our data suggest that Hp-Vam3p may be functionally redundant in peroxisome degradation. Remarkably, deletion of Hp-VAM7 also significantly affected peroxisome biogenesis and resulted in organelles with multiple, membrane-enclosed compartments. These morphological defects became first visible in cells that were in the mid-exponential growth phase of cultivation on methanol, and were correlated with accumulation of electron-dense extensions that were connected to mitochondria.
Original languageEnglish
Pages (from-to)985 - 997
Number of pages13
JournalFems Yeast Research
Volume5
Issue number11
DOIs
Publication statusPublished - Nov-2005

Keywords

  • Yeast
  • SNARE
  • Selective organelle degradation
  • Pexophagy
  • Peroxisome
  • Autophagy

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