Interactions with LC3 and polyubiquitin chains link nbr1 to autophagic protein turnover

Nbr1, a ubiquitous kinase scaffold protein, contains a PB1, and a ubiquitin-associated (UBA) domain. We show here that the nbr1 UBA domain binds to lysine-48 and -63 linked polyubiquitin-B chains. Nbr1 also binds to the autophagic effector protein LC3-A via a novel binding site. Ubiquitin-binding, but not PB1-mediated p62/SQSTM1 interaction, is required to target nbr1 to LC3 and polyubiquitin-positive bodies. Nbr1 binds additionally to proteins implicated in ubiquitin-mediated protein turnover and vesicle trafficking: ubiquitin-specific peptidases USP8, and the endosomal transport regulator p14/Robld3. Nbr1 thus contributes to specific steps in protein turnover regulation disrupted in several hereditary human diseases. Structured summary: MINT-7034452: USP8 (uniprotkb: P40818) physically interacts (MI: 0218) with NBR1 (uniprotkb: Q14596) by pull down (MI: 0096) MINT-7034438: SQSTM1 (uniprotkb: Q13501) and LC3 (uniprotkb: Q9H492) colocalize (MI: 0403) by fluorescence microscopy (MI: 0416) MINT-7034309: NBR1 (uniprotkb: Q14596) physically interacts (MI: 0218) with Ubiquitin (uniprotkb: P62988) by pull down (MI: 0096) MINT-7034323: NBR1 (uniprotkb: P97432) physically interacts (MI: 0218) with Ubiquitin (uniprotkb: P62988) by pull down (MI: 0096) MINT-7034233: NBR1 (uniprotkb: Q14596) physically interacts (MI: 0218) with USP8 (uniprotkb: P40818) by two hybrid (MI: 0018) MINT-7034207: NBR1 (uniprotkb: Q14596) physically interacts (MI: 0218) with Robld3 (uniprotkb: Q9JHS3) by two hybrid (MI: 0018) MINT-7034400, MINT-7034418: NBR1 (uniprotkb: Q14596) and LC3 (uniprotkb: Q9H492) colocalize (MI: 0403) by fluorescence microscopy (MI: 0416) MINT-7034167: NBR1 (uniprotkb: Q14596) physically interacts (MI: 0218) with Ubiquitin B (uniprotkb: Q78XY9) by two hybrid (MI: 0018) MINT-7034470: NBR1 (uniprotkb: Q14596) and USP8 (uniprotkb: P40818) colocalize (MI: 0403) by fluorescence microscopy (MI: 0416) MINT-7034194: NBR1 (uniprotkb: Q14596) physically interacts (MI: 0218) with LC3-A (uniprotkb: Q91VR7) by two hybrid (MI: 0018) MINT-7034336: SQSTM1 (uniprotkb: Q13501) physically interacts (MI: 0218) with Ubiquitin (uniprotkb: P62988) by pull down (MI: 0096) MINT-7034375: NBR1 (uniprotkb: Q14596) physically interacts (MI: 0218) with LC3 (uniprotkb: Q9H492) by pull down (MI: 0096) MINT-7034350: NBR1 (uniprotkb: Q14596) and Ubiquitin (uniprotkb: P62988) colocalize (MI: 0403) by fluorescence microscopy (MI: 0416) MINT-7034181: NBR1 (uniprotkb: Q14596) physically interacts (MI: 0218) with Tmed10 (uniprotkb: Q9D1D4) by two hybrid (MI: 0018) MINT-7034220: NBR1 (uniprotkb: Q14596) physically interacts (MI: 0218) with ube2o (uniprotkb: Q6ZPJ3) by two hybrid (MI: 0018) (C) 2009 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.