Carbon and nitrogen depletion-induced nucleophagy and selective autophagic sequestration of a whole nucleus in multinucleate cells of the filamentous fungus Aspergillus oryzae.
Autophagy is a conserved cellular degradation process in eukaryotes, in which cytoplasmic components and organelles are digested in vacuoles/lysosomes. Recently, autophagic degradation of nuclear materials, termed "nucleophagy", has been reported. In the multinucleate filamentous fungus Aspergillus oryzae, a whole nucleus is degraded by nucleophagy after prolonged culture. While developing an H2B-EGFP processing assay for the evaluation of nucleophagy in A. oryzae, we found that nucleophagy is efficiently induced by carbon or nitrogen depletion. Microscopic observations in a carbon depletion condition clearly demonstrated that autophagosomes selectively sequester a particular nucleus, despite the presence of multiple nuclei in the same cell. Furthermore, AoNsp1, the A. oryzae homolog of the yeast nucleoporin Nsp1p, mainly localized at the nuclear periphery, but its localization was restricted to the opposite side of the autophagosome being formed around a nucleus. In contrast, the perinuclear ER visualized with the calnexin AoClxA was not morphologically affected by nucleophagy. The findings of nucleophagy-inducing conditions enabled us to characterize the morphological process of autophagic degradation of a whole nucleus in multinucleate cells.
Department of Biotechnology, The University of Tokyo.
Takashi
T
Kikuma
Department of Biotechnology, The University of Tokyo.
Takahiro
T
Mitani
Department of Biotechnology, The University of Tokyo.
Takahiro
T
Kohara
Department of Biotechnology, The University of Tokyo.
Jun-Ichi
JI
Maruyama
Department of Biotechnology, The University of Tokyo.
Katsuhiko
K
Kitamoto
D001236:Aspergillus oryzae / Q000166:cytology / Q000378:metabolism*; D001343:Autophagy; D002244:Carbon / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
D003470:Culture Media; D005656:Fungal Proteins; C062748:NSP1 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D002244:Carbon; D009584:Nitrogen
Aspergillus oryzae; autophagy; filamentous fungi; multinucleate cell; nucleophagy