title: Atg8 is essential for macropexophagy in Hansenula polymorpha.
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.
authors.affiliation: Eukaryotic Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, PO Box 14, 9750 AA Haren, the Netherlands.
authors.forename: Iryna
authors.initials: I
authors.lastname: Monastyrska
authors.forename: Meis
authors.initials: M
authors.lastname: van der Heide
authors.forename: Arjen M
authors.initials: AM
authors.lastname: Krikken
authors.forename: Jan A K W
authors.initials: JA
authors.lastname: Kiel
authors.forename: Ida J
authors.initials: IJ
authors.lastname: van der Klei
authors.forename: Marten
authors.initials: M
authors.lastname: Veenhuis
mesh_terms: D000595:Amino Acid Sequence; D001343:Autophagy / Q000235:genetics; D001692:Biological Transport; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D020675:Peroxisomes / Q000378:metabolism*; D010843:Pichia / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins