2022/01/23 更新

写真a

ヒラタ エリ
平田 恵理
所属
研究院(研究機関) ナノ・ライフ創新研究機構
職名
次席研究員(研究院講師)
 

研究分野

  • 分子生物学   酵母

論文

  • Liquidity Is a Critical Determinant for Selective Autophagy of Protein Condensates.

    Akinori Yamasaki, Jahangir Md Alam, Daisuke Noshiro, Eri Hirata, Yuko Fujioka, Kuninori Suzuki, Yoshinori Ohsumi, Nobuo N Noda

    Molecular cell   77 ( 6 ) 1163 - 1175  2020年03月  [査読有り]  [国際誌]

     概要を見る

    Clearance of biomolecular condensates by selective autophagy is thought to play a crucial role in cellular homeostasis. However, the mechanism underlying selective autophagy of condensates and whether liquidity determines a condensate's susceptibility to degradation by autophagy remain unknown. Here, we show that the selective autophagic cargo aminopeptidase I (Ape1) undergoes phase separation to form semi-liquid droplets. The Ape1-specific receptor protein Atg19 localizes to the surface of Ape1 droplets both in vitro and in vivo, with the "floatability" of Atg19 preventing its penetration into droplets. In vitro reconstitution experiments reveal that Atg19 and lipidated Atg8 are necessary and sufficient for selective sequestration of Ape1 droplets by membranes. This sequestration is impaired by mutational solidification of Ape1 droplets or diminished ability of Atg19 to float. Taken together, we propose that cargo liquidity and the presence of sufficient amounts of autophagic receptor on cargo are crucial for selective autophagy of biomolecular condensates.

    DOI PubMed

  • Atg2 mediates direct lipid transfer between membranes for autophagosome formation.

    Takuo Osawa, Tetsuya Kotani, Tatsuya Kawaoka, Eri Hirata, Kuninori Suzuki, Hitoshi Nakatogawa, Yoshinori Ohsumi, Nobuo N Noda

    Nature structural & molecular biology   26 ( 4 ) 281 - 288  2019年04月  [査読有り]  [国際誌]

     概要を見る

    A key event in autophagy is autophagosome formation, whereby the newly synthesized isolation membrane (IM) expands to form a complete autophagosome using endomembrane-derived lipids. Atg2 physically links the edge of the expanding IM with the endoplasmic reticulum (ER), a role that is essential for autophagosome formation. However, the molecular function of Atg2 during ER-IM contact remains unclear, as does the mechanism of lipid delivery to the IM. Here we show that the conserved amino-terminal region of Schizosaccharomyces pombe Atg2 includes a lipid-transfer-protein-like hydrophobic cavity that accommodates phospholipid acyl chains. Atg2 bridges highly curved liposomes, thereby facilitating efficient phospholipid transfer in vitro, a function that is inhibited by mutations that impair autophagosome formation in vivo. These results suggest that Atg2 acts as a lipid-transfer protein that supplies phospholipids for autophagosome formation.

    DOI PubMed

  • Global study of holistic morphological effectors in the budding yeast Saccharomyces cerevisiae.

    Godai Suzuki, Yang Wang, Karen Kubo, Eri Hirata, Shinsuke Ohnuki, Yoshikazu Ohya

    BMC genomics   19 ( 1 ) 149 - 149  2018年02月  [査読有り]  [国際誌]

     概要を見る

    BACKGROUND: The size of the phenotypic effect of a gene has been thoroughly investigated in terms of fitness and specific morphological traits in the budding yeast Saccharomyces cerevisiae, but little is known about gross morphological abnormalities. RESULTS: We identified 1126 holistic morphological effectors that cause severe gross morphological abnormality when deleted, and 2241 specific morphological effectors with weak holistic effects but distinctive effects on yeast morphology. Holistic effectors fell into many gene function categories and acted as network hubs, affecting a large number of morphological traits, interacting with a large number of genes, and facilitating high protein expression. Holistic morphological abnormality was useful for estimating the importance of a gene to morphology. The contribution of gene importance to fitness and morphology could be used to efficiently classify genes into functional groups. CONCLUSION: Holistic morphological abnormality can be used as a reproducible and reliable gene feature for high-dimensional morphological phenotyping. It can be used in many functional genomic applications.

    DOI PubMed

  • Atg4 plays an important role in efficient expansion of autophagic isolation membranes by cleaving lipidated Atg8 in Saccharomyces cerevisiae.

    Eri Hirata, Yoshikazu Ohya, Kuninori Suzuki

    PloS one   12 ( 7 ) e0181047  2017年  [査読有り]  [国際誌]

     概要を見る

    Autophagy, an intracellular degradation system, is highly conserved among eukaryotes from yeast to mammalian cells. In the yeast Saccharomyces cerevisiae, most Atg (autophagy-related) proteins, which are essential for autophagosome formation, are recruited to a restricted region close to the vacuole, termed the vacuole-isolation membrane contact site (VICS), upon induction of autophagy. Subsequently, the isolation membrane (IM) expands and sequesters cytoplasmic materials to become a closed autophagosome. In S. cerevisiae, the ubiquitin-like protein Atg8 is C-terminally conjugated to the phospholipid phosphatidylethanolamine (PE) to generate Atg8-PE. During autophagosome formation, Atg8-PE is cleaved by Atg4 to release delipidated Atg8 (Atg8G116) and PE. Although delipidation of Atg8-PE is important for autophagosome formation, it remains controversial whether the delipidation reaction is required for targeting of Atg8 to the VICS or for subsequent IM expansion. We used an IM visualization technique to clearly demonstrate that delipidation of Atg8-PE is dispensable for targeting of Atg8 to the VICS, but required for IM expansion. Moreover, by overexpressing Atg8G116, we showed that the delipidation reaction of Atg8-PE by Atg4 plays an important role in efficient expansion of the IM other than supplying unlipidated Atg8G116. Finally, we suggested the existence of biological membranes at the Atg8-labeled structures in Atg8-PE delipidation-defective cells, but not at those in atg2Δ cells. Taken together, it is likely that Atg2 is involved in localization of biological membranes to the VICS, where Atg4 is responsible for IM expansion.

    DOI PubMed

  • Visualization of Atg3 during autophagosome formation in Saccharomyces cerevisiae.

    Meipin Ngu, Eri Hirata, Kuninori Suzuki

    The Journal of biological chemistry   290 ( 13 ) 8146 - 53  2015年03月  [査読有り]  [国際誌]

     概要を見る

    Macroautophagy (autophagy) is a highly conserved cellular recycling process involved in degradation of eukaryotic cellular components. During autophagy, macromolecules and organelles are sequestered into the double-membrane autophagosome and degraded in the vacuole/lysosome. Autophagy-related 8 (Atg8), a core Atg protein essential for autophagosome formation, is a marker of several autophagic structures: the pre-autophagosomal structure (PAS), isolation membrane (IM), and autophagosome. Atg8 is conjugated to phosphatidylethanolamine (PE) through a ubiquitin-like conjugation system to yield Atg8-PE; this reaction is called Atg8 lipidation. Although the mechanisms of Atg8 lipidation have been well studied in vitro, the cellular locale of Atg8 lipidation remains enigmatic. Atg3 is an E2-like enzyme that catalyzes the conjugation reaction between Atg8 and PE. Therefore, we hypothesized that the localization of Atg3 would provide insights about the site of the lipidation reaction. To explore this idea, we constructed functional GFP-tagged Atg3 (Atg3-GFP) by inserting the GFP portion immediately after the handle region of Atg3. During autophagy, Atg3-GFP transiently formed a single dot per cell on the vacuolar membrane. This Atg3-GFP dot colocalized with 2× mCherry-tagged Atg8, demonstrating that Atg3 is localized to autophagic structures. Furthermore, we found that Atg3-GFP is localized to the IM by fine-localization analysis. The localization of Atg3 suggests that Atg3 plays an important role in autophagosome formation at the IM.

    DOI PubMed