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  1. Article ; Online: Mouse oocytes sequester aggregated proteins in degradative super-organelles.

    Zaffagnini, Gabriele / Cheng, Shiya / Salzer, Marion C / Pernaute, Barbara / Duran, Juan Manuel / Irimia, Manuel / Schuh, Melina / Böke, Elvan

    Cell

    2024  Volume 187, Issue 5, Page(s) 1109–1126.e21

    Abstract: Oocytes are among the longest-lived cells in the body and need to preserve their cytoplasm to support proper embryonic development. Protein aggregation is a major threat for intracellular homeostasis in long-lived cells. How oocytes cope with protein ... ...

    Abstract Oocytes are among the longest-lived cells in the body and need to preserve their cytoplasm to support proper embryonic development. Protein aggregation is a major threat for intracellular homeostasis in long-lived cells. How oocytes cope with protein aggregation during their extended life is unknown. Here, we find that mouse oocytes accumulate protein aggregates in specialized compartments that we named endolysosomal vesicular assemblies (ELVAs). Combining live-cell imaging, electron microscopy, and proteomics, we found that ELVAs are non-membrane-bound compartments composed of endolysosomes, autophagosomes, and proteasomes held together by a protein matrix formed by RUFY1. Functional assays revealed that in immature oocytes, ELVAs sequester aggregated proteins, including TDP-43, and degrade them upon oocyte maturation. Inhibiting degradative activity in ELVAs leads to the accumulation of protein aggregates in the embryo and is detrimental for embryo survival. Thus, ELVAs represent a strategy to safeguard protein homeostasis in long-lived cells.
    MeSH term(s) Animals ; Female ; Mice ; Autophagosomes ; Cytoplasmic Vesicles/metabolism ; Lysosomes/metabolism ; Oocytes/cytology ; Oocytes/metabolism ; Proteasome Endopeptidase Complex ; Protein Aggregates ; Proteolysis
    Chemical Substances Proteasome Endopeptidase Complex (EC 3.4.25.1) ; Protein Aggregates
    Language English
    Publishing date 2024-02-20
    Publishing country United States
    Document type Journal Article
    ZDB-ID 187009-9
    ISSN 1097-4172 ; 0092-8674
    ISSN (online) 1097-4172
    ISSN 0092-8674
    DOI 10.1016/j.cell.2024.01.031
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: A mathematical model of p62-ubiquitin aggregates in autophagy.

    Delacour, Julia / Doumic, Marie / Martens, Sascha / Schmeiser, Christian / Zaffagnini, Gabriele

    Journal of mathematical biology

    2021  Volume 84, Issue 1-2, Page(s) 3

    Abstract: Aggregation of ubiquitinated cargo by oligomers of the protein p62 is an important preparatory step in cellular autophagy. In this work a mathematical model for the dynamics of these heterogeneous aggregates in the form of a system of ordinary ... ...

    Abstract Aggregation of ubiquitinated cargo by oligomers of the protein p62 is an important preparatory step in cellular autophagy. In this work a mathematical model for the dynamics of these heterogeneous aggregates in the form of a system of ordinary differential equations is derived and analyzed. Three different parameter regimes are identified, where either aggregates are unstable, or their size saturates at a finite value, or their size grows indefinitely as long as free particles are abundant. The boundaries of these regimes as well as the finite size in the second case can be computed explicitly. The growth in the third case (quadratic in time) can also be made explicit by formal asymptotic methods. In the absence of rigorous results the dynamic stability of these structures has been investigated by numerical simulations. A comparison with recent experimental results permits a partial parametrization of the model.
    MeSH term(s) Autophagy ; Models, Theoretical ; Proteins ; Sequestosome-1 Protein/metabolism ; Ubiquitin/metabolism
    Chemical Substances Proteins ; Sequestosome-1 Protein ; Ubiquitin
    Language English
    Publishing date 2021-12-14
    Publishing country Germany
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 187101-8
    ISSN 1432-1416 ; 0303-6812
    ISSN (online) 1432-1416
    ISSN 0303-6812
    DOI 10.1007/s00285-021-01659-2
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Mechanisms of Selective Autophagy.

    Zaffagnini, Gabriele / Martens, Sascha

    Journal of molecular biology

    2016  Volume 428, Issue 9 Pt A, Page(s) 1714–1724

    Abstract: Selective autophagy contributes to intracellular homeostasis by mediating the degradation of cytoplasmic material such as aggregated proteins, damaged or over-abundant organelles, and invading pathogens. The molecular machinery for selective autophagy ... ...

    Abstract Selective autophagy contributes to intracellular homeostasis by mediating the degradation of cytoplasmic material such as aggregated proteins, damaged or over-abundant organelles, and invading pathogens. The molecular machinery for selective autophagy must ensure efficient recognition and sequestration of the cargo within autophagosomes. Cargo specificity can be mediated by autophagic cargo receptors that specifically bind the cargo material and the autophagosomal membrane. Here we review the recent insights into the mechanisms that enable cargo receptors to confer selectivity and exclusivity to the autophagic process. We also discuss their different roles during starvation-induced and selective autophagy. We propose to classify autophagic events into cargo-independent and cargo-induced autophagosome formation events.
    MeSH term(s) Autophagosomes/metabolism ; Autophagy ; Homeostasis
    Language English
    Publishing date 2016--08
    Publishing country England
    Document type Journal Article ; Review ; Research Support, Non-U.S. Gov't
    ZDB-ID 80229-3
    ISSN 1089-8638 ; 0022-2836
    ISSN (online) 1089-8638
    ISSN 0022-2836
    DOI 10.1016/j.jmb.2016.02.004
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Mechanisms of Selective Autophagy

    Zaffagnini, Gabriele / Martens, Sascha

    Journal of Molecular Biology. 2016 May 08, v. 428

    2016  

    Abstract: Selective autophagy contributes to intracellular homeostasis by mediating the degradation of cytoplasmic material such as aggregated proteins, damaged or over-abundant organelles, and invading pathogens. The molecular machinery for selective autophagy ... ...

    Abstract Selective autophagy contributes to intracellular homeostasis by mediating the degradation of cytoplasmic material such as aggregated proteins, damaged or over-abundant organelles, and invading pathogens. The molecular machinery for selective autophagy must ensure efficient recognition and sequestration of the cargo within autophagosomes. Cargo specificity can be mediated by autophagic cargo receptors that specifically bind the cargo material and the autophagosomal membrane. Here we review the recent insights into the mechanisms that enable cargo receptors to confer selectivity and exclusivity to the autophagic process. We also discuss their different roles during starvation-induced and selective autophagy. We propose to classify autophagic events into cargo-independent and cargo-induced autophagosome formation events.
    Keywords autophagy ; homeostasis ; organelles ; pathogens ; receptors
    Language English
    Dates of publication 2016-0508
    Size p. 1714-1724.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 80229-3
    ISSN 1089-8638 ; 0022-2836
    ISSN (online) 1089-8638
    ISSN 0022-2836
    DOI 10.1016/j.jmb.2016.02.004
    Database NAL-Catalogue (AGRICOLA)

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  5. Article ; Online: Comparative analysis of vertebrates reveals that mouse primordial oocytes do not contain a Balbiani body.

    Dhandapani, Laasya / Salzer, Marion C / Duran, Juan M / Zaffagnini, Gabriele / De Guirior, Cristian / Martínez-Zamora, Maria Angeles / Böke, Elvan

    Journal of cell science

    2022  Volume 135, Issue 1

    Abstract: Oocytes spend the majority of their lifetime in a primordial state. The cellular and molecular biology of primordial oocytes is largely unexplored; yet, it is necessary to study them to understand the mechanisms through which oocytes maintain cellular ... ...

    Abstract Oocytes spend the majority of their lifetime in a primordial state. The cellular and molecular biology of primordial oocytes is largely unexplored; yet, it is necessary to study them to understand the mechanisms through which oocytes maintain cellular fitness for decades, and why they eventually fail with age. Here, we develop enabling methods for live-imaging-based comparative characterization of Xenopus, mouse and human primordial oocytes. We show that primordial oocytes in all three vertebrate species contain active mitochondria, Golgi and lysosomes. We further demonstrate that human and Xenopus oocytes have a Balbiani body characterized by a dense accumulation of mitochondria in their cytoplasm. However, despite previous reports, we did not find a Balbiani body in mouse oocytes. Instead, we demonstrate that what was previously used as a marker for the Balbiani body in mouse primordial oocytes is in fact a ring-shaped Golgi that is not functionally associated with oocyte dormancy. This study provides the first insights into the organization of the cytoplasm in mammalian primordial oocytes, and clarifies the relative advantages and limitations of choosing different model organisms for studying oocyte dormancy.
    MeSH term(s) Animals ; Cytoplasm ; Mice ; Mitochondria ; Oocytes/metabolism ; Organelles ; Xenopus laevis
    Language English
    Publishing date 2022-01-10
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2993-2
    ISSN 1477-9137 ; 0021-9533
    ISSN (online) 1477-9137
    ISSN 0021-9533
    DOI 10.1242/jcs.259394
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Oligomerization of p62 allows for selection of ubiquitinated cargo and isolation membrane during selective autophagy.

    Wurzer, Bettina / Zaffagnini, Gabriele / Fracchiolla, Dorotea / Turco, Eleonora / Abert, Christine / Romanov, Julia / Martens, Sascha

    eLife

    2015  Volume 4, Page(s) e08941

    Abstract: Autophagy is a major pathway for the clearance of harmful material from the cytoplasm. During autophagy, cytoplasmic material is delivered into the lysosomal system by organelles called autophagosomes. Autophagosomes form in a de novo manner and, in the ... ...

    Abstract Autophagy is a major pathway for the clearance of harmful material from the cytoplasm. During autophagy, cytoplasmic material is delivered into the lysosomal system by organelles called autophagosomes. Autophagosomes form in a de novo manner and, in the course of their formation, isolate cargo material from the rest of the cytoplasm. Cargo specificity is conferred by autophagic cargo receptors that selectively link the cargo to the autophagosomal membrane decorated with ATG8 family proteins such as LC3B. Here we show that the human cargo receptor p62/SQSTM-1 employs oligomerization to stabilize its interaction with LC3B and linear ubiquitin when they are clustered on surfaces. Thus, oligomerization enables p62 to simultaneously select for the isolation membrane and the ubiquitinated cargo. We further show in a fully reconstituted system that the interaction of p62 with ubiquitin and LC3B is sufficient to bend the membrane around the cargo.
    MeSH term(s) Adaptor Proteins, Signal Transducing/metabolism ; Autophagy ; Humans ; Intracellular Membranes/metabolism ; Microtubule-Associated Proteins/metabolism ; Protein Binding ; Protein Multimerization ; Sequestosome-1 Protein ; Ubiquitin/metabolism
    Chemical Substances Adaptor Proteins, Signal Transducing ; MAP1LC3B protein, human ; Microtubule-Associated Proteins ; SQSTM1 protein, human ; Sequestosome-1 Protein ; Ubiquitin
    Language English
    Publishing date 2015-09-28
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2687154-3
    ISSN 2050-084X ; 2050-084X
    ISSN (online) 2050-084X
    ISSN 2050-084X
    DOI 10.7554/eLife.08941
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: p62 filaments capture and present ubiquitinated cargos for autophagy.

    Zaffagnini, Gabriele / Savova, Adriana / Danieli, Alberto / Romanov, Julia / Tremel, Shirley / Ebner, Michael / Peterbauer, Thomas / Sztacho, Martin / Trapannone, Riccardo / Tarafder, Abul K / Sachse, Carsten / Martens, Sascha

    The EMBO journal

    2018  Volume 37, Issue 5

    Abstract: The removal of misfolded, ubiquitinated proteins is an essential part of the protein quality control. The ubiquitin-proteasome system (UPS) and autophagy are two interconnected pathways that mediate the degradation of such proteins. During autophagy, ... ...

    Abstract The removal of misfolded, ubiquitinated proteins is an essential part of the protein quality control. The ubiquitin-proteasome system (UPS) and autophagy are two interconnected pathways that mediate the degradation of such proteins. During autophagy, ubiquitinated proteins are clustered in a p62-dependent manner and are subsequently engulfed by autophagosomes. However, the nature of the protein substrates targeted for autophagy is unclear. Here, we developed a reconstituted system using purified components and show that p62 and ubiquitinated proteins spontaneously coalesce into larger clusters. Efficient cluster formation requires substrates modified with at least two ubiquitin chains longer than three moieties and is based on p62 filaments cross-linked by the substrates. The reaction is inhibited by free ubiquitin, K48-, and K63-linked ubiquitin chains, as well as by the autophagosomal marker LC3B, suggesting a tight cross talk with general proteostasis and autophagosome formation. Our study provides mechanistic insights on how substrates are channeled into autophagy.
    MeSH term(s) Autophagosomes/physiology ; Autophagy/physiology ; Cell Line, Tumor ; Humans ; Microtubule-Associated Proteins/metabolism ; Protein Aggregation, Pathological/pathology ; Protein Aggregation, Pathological/prevention & control ; Protein Folding ; RNA-Binding Proteins/metabolism ; Ubiquitin/metabolism ; Ubiquitinated Proteins/metabolism
    Chemical Substances MAP1LC3B protein, human ; Microtubule-Associated Proteins ; P62 protein, human ; RNA-Binding Proteins ; Ubiquitin ; Ubiquitinated Proteins
    Language English
    Publishing date 2018-01-17
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 586044-1
    ISSN 1460-2075 ; 0261-4189
    ISSN (online) 1460-2075
    ISSN 0261-4189
    DOI 10.15252/embj.201798308
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Phasing out the bad-How SQSTM1/p62 sequesters ubiquitinated proteins for degradation by autophagy.

    Zaffagnini, Gabriele / Savova, Adriana / Danieli, Alberto / Romanov, Julia / Tremel, Shirley / Ebner, Michael / Peterbauer, Thomas / Sztacho, Martin / Trapannone, Riccardo / Tarafder, Abul K / Sachse, Carsten / Martens, Sascha

    Autophagy

    2018  Volume 14, Issue 7, Page(s) 1280–1282

    Abstract: The degradation of misfolded, ubiquitinated proteins is essential for cellular homeostasis. These proteins are primarily degraded by the ubiquitin-proteasome system (UPS) and macroautophagy/autophagy serves as a backup mechanism when the UPS is ... ...

    Abstract The degradation of misfolded, ubiquitinated proteins is essential for cellular homeostasis. These proteins are primarily degraded by the ubiquitin-proteasome system (UPS) and macroautophagy/autophagy serves as a backup mechanism when the UPS is overloaded. How autophagy and the UPS are coordinated is not fully understood. During the autophagy of misfolded, ubiquitinated proteins, referred to as aggrephagy, substrate proteins are clustered into larger structures in a SQSTM1/p62-dependent manner before they are sequestered by phagophores, the precursors to autophagosomes. We have recently shown that SQSTM1/p62 and ubiquitinated proteins spontaneously phase separate into micrometer-sized clusters in vitro. This enabled us to characterize the properties of the ubiquitin-positive substrates that are necessary for the SQSTM1/p62-mediated cluster formation. Our results suggest that aggrephagy is triggered by the accumulation of substrates with multiple ubiquitin chains and that the process can be inhibited by active proteasomes.
    MeSH term(s) Autophagy ; Humans ; Models, Biological ; Proteasome Endopeptidase Complex/metabolism ; Sequestosome-1 Protein/metabolism ; Ubiquitin/metabolism ; Ubiquitinated Proteins/metabolism
    Chemical Substances Sequestosome-1 Protein ; Ubiquitin ; Ubiquitinated Proteins ; Proteasome Endopeptidase Complex (EC 3.4.25.1)
    Language English
    Publishing date 2018-07-20
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2454135-7
    ISSN 1554-8635 ; 1554-8627
    ISSN (online) 1554-8635
    ISSN 1554-8627
    DOI 10.1080/15548627.2018.1462079
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: FIP200 Claw Domain Binding to p62 Promotes Autophagosome Formation at Ubiquitin Condensates.

    Turco, Eleonora / Witt, Marie / Abert, Christine / Bock-Bierbaum, Tobias / Su, Ming-Yuan / Trapannone, Riccardo / Sztacho, Martin / Danieli, Alberto / Shi, Xiaoshan / Zaffagnini, Gabriele / Gamper, Annamaria / Schuschnig, Martina / Fracchiolla, Dorotea / Bernklau, Daniel / Romanov, Julia / Hartl, Markus / Hurley, James H / Daumke, Oliver / Martens, Sascha

    Molecular cell

    2019  Volume 74, Issue 2, Page(s) 330–346.e11

    Abstract: The autophagy cargo receptor p62 facilitates the condensation of misfolded, ubiquitin-positive proteins and their degradation by autophagy, but the molecular mechanism of p62 signaling to the core autophagy machinery is unclear. Here, we show that ... ...

    Abstract The autophagy cargo receptor p62 facilitates the condensation of misfolded, ubiquitin-positive proteins and their degradation by autophagy, but the molecular mechanism of p62 signaling to the core autophagy machinery is unclear. Here, we show that disordered residues 326-380 of p62 directly interact with the C-terminal region (CTR) of FIP200. Crystal structure determination shows that the FIP200 CTR contains a dimeric globular domain that we designated the "Claw" for its shape. The interaction of p62 with FIP200 is mediated by a positively charged pocket in the Claw, enhanced by p62 phosphorylation, mutually exclusive with the binding of p62 to LC3B, and it promotes degradation of ubiquitinated cargo by autophagy. Furthermore, the recruitment of the FIP200 CTR slows the phase separation of ubiquitinated proteins by p62 in a reconstituted system. Our data provide the molecular basis for a crosstalk between cargo condensation and autophagosome formation.
    MeSH term(s) Autophagosomes/chemistry ; Autophagosomes/metabolism ; Autophagy/genetics ; Autophagy-Related Proteins ; Crystallography, X-Ray ; Humans ; Microtubule-Associated Proteins/chemistry ; Microtubule-Associated Proteins/genetics ; Protein Conformation ; Protein Interaction Maps/genetics ; Protein-Tyrosine Kinases/chemistry ; Protein-Tyrosine Kinases/genetics ; Proteolysis ; Sequestosome-1 Protein/chemistry ; Sequestosome-1 Protein/genetics ; Signal Transduction/genetics ; Ubiquitin/chemistry ; Ubiquitin/genetics
    Chemical Substances Autophagy-Related Proteins ; MAP1LC3B protein, human ; Microtubule-Associated Proteins ; RB1CC1 protein, human ; SQSTM1 protein, human ; Sequestosome-1 Protein ; Ubiquitin ; Protein-Tyrosine Kinases (EC 2.7.10.1)
    Language English
    Publishing date 2019-03-07
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 1415236-8
    ISSN 1097-4164 ; 1097-2765
    ISSN (online) 1097-4164
    ISSN 1097-2765
    DOI 10.1016/j.molcel.2019.01.035
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: How RB1CC1/FIP200 claws its way to autophagic engulfment of SQSTM1/p62-ubiquitin condensates.

    Turco, Eleonora / Witt, Marie / Abert, Christine / Bock-Bierbaum, Tobias / Su, Ming-Yuan / Trapannone, Riccardo / Sztacho, Martin / Danieli, Alberto / Shi, Xiaoshan / Zaffagnini, Gabriele / Gamper, Annamaria / Schuschnig, Martina / Fracchiolla, Dorotea / Bernklau, Daniel / Romanov, Julia / Hartl, Markus / Hurley, James H / Daumke, Oliver / Martens, Sascha

    Autophagy

    2019  Volume 15, Issue 8, Page(s) 1475–1477

    Abstract: Macroautophagy/autophagy mediates the degradation of ubiquitinated aggregated proteins within lysosomes in a process known as aggrephagy. The cargo receptor SQSTM1/p62 condenses aggregated proteins into larger structures and links them to the nascent ... ...

    Abstract Macroautophagy/autophagy mediates the degradation of ubiquitinated aggregated proteins within lysosomes in a process known as aggrephagy. The cargo receptor SQSTM1/p62 condenses aggregated proteins into larger structures and links them to the nascent autophagosomal membrane (phagophore). How the condensation reaction and autophagosome formation are coupled is unclear. We recently discovered that a region of SQSTM1 containing its LIR motif directly interacts with RB1CC1/FIP200, a protein acting at early stages of autophagosome formation. Determination of the structure of the C-terminal region of RB1CC1 revealed a claw-shaped domain. Using a structure-function approach, we show that the interaction of SQSTM1 with the RB1CC1 claw domain is crucial for the productive recruitment of the autophagy machinery to ubiquitin-positive condensates and their subsequent degradation by autophagy. We also found that concentrated Atg8-family proteins on the phagophore displace RB1CC1 from SQSTM1, suggesting an intrinsic directionality in the process of autophagosome formation. Ultimately, our study reveals how the interplay of SQSTM1 and RB1CC1 couples cargo condensation to autophagosome formation.
    MeSH term(s) Animals ; Autophagosomes/metabolism ; Autophagy ; Autophagy-Related Proteins/metabolism ; Humans ; Models, Biological ; Protein Binding ; Sequestosome-1 Protein/metabolism ; Ubiquitin/metabolism
    Chemical Substances Autophagy-Related Proteins ; Sequestosome-1 Protein ; Ubiquitin
    Language English
    Publishing date 2019-05-22
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2454135-7
    ISSN 1554-8635 ; 1554-8627
    ISSN (online) 1554-8635
    ISSN 1554-8627
    DOI 10.1080/15548627.2019.1615306
    Database MEDical Literature Analysis and Retrieval System OnLINE

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