title: The evolutionarily conserved interaction between LC3 and p62 selectively mediates autophagy-dependent degradation of mutant huntingtin.
abstract: Mammalian p62/sequestosome-1 protein binds to both LC3, the mammalian homologue of yeast Atg8, and polyubiquitinated cargo proteins destined to undergo autophagy-mediated degradation. We previously identified a cargo receptor-binding domain in Atg8 that is essential for its interaction with the cargo receptor Atg19 in selective autophagic processes in yeast. We, thus, sought to determine whether this interaction is evolutionally conserved from yeast to mammals. Using an amino acid replacement approach, we demonstrate that cells expressing mutant LC3 (LC3-K30D, LC3-K51A, or LC3-L53A) all exhibit defective lipidation of LC3, a disrupted LC3-p62 interaction, and impaired autophagic degradation of p62, suggesting that the p62-binding site of LC3 is localized within an evolutionarily conserved domain. Importantly, whereas cells expressing these LC3 mutants exhibited similar overall autophagic activity comparable to that of cells expressing wild-type LC3, autophagy-mediated clearance of the aggregation-prone mutant Huntingtin was defective in the mutant-expressing cells. Together, these results suggest that p62 directly binds to the evolutionarily conserved cargo receptor-binding domain of Atg8/LC3 and selectively mediates the clearance of mutant Huntingtin.
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, ICOB 238, 128 Sec. 2 Academia Rd., Taipei 11529, Taiwan.
authors.forename: Ying-Tsen
authors.initials: YT
authors.lastname: Tung
authors.forename: Wen-Ming
authors.initials: WM
authors.lastname: Hsu
authors.forename: Hsinyu
authors.initials: H
authors.lastname: Lee
authors.forename: Wei-Pang
authors.initials: WP
authors.lastname: Huang
authors.forename: Yung-Feng
authors.initials: YF
authors.lastname: Liao
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D024361:Amino Acids, Basic / Q000378:metabolism; D000818:Animals; D001343:Autophagy; D016923:Cell Death; D002460:Cell Line; D019143:Evolution, Molecular; D006801:Humans; D000071058:Huntingtin Protein; D057927:Hydrophobic and Hydrophilic Interactions; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D051381:Rats; D000071456:Sequestosome-1 Protein; D013329:Structure-Activity Relationship; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D024361:Amino Acids, Basic; D000071058:Huntingtin Protein; D008869:Microtubule-Associated Proteins; D050505:Mutant Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D000071456:Sequestosome-1 Protein; D025801:Ubiquitin; C086055:HTT protein, human; C526109:Anxa3 protein, rat; C099718:SQSTM1 protein, human