How RB1CC1/FIP200 claws its way to autophagic engulfment of SQSTM1/p62-ubiquitin condensates

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 con...

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Bibliographic Details
Published in:Autophagy 2019-08, Vol.15 (8), p.1475-1477
Main Authors: 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
Format: Article
Language:English
Subjects:
Aggrephagy
Animals
Atg8
Autophagic Punctum
autophagosome
Autophagosomes - metabolism
Autophagy
Autophagy-Related Proteins - metabolism
cargo receptor
Humans
Models, Biological
phase separation
Protein Binding
protein quality control
Sequestosome-1 Protein - metabolism
Ubiquitin - metabolism
ULK1
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Summary: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.
ISSN:1554-8627
1554-8635
DOI:10.1080/15548627.2019.1615306