title: Rab GTPase-activating proteins in autophagy: regulation of endocytic and autophagy pathways by direct binding to human ATG8 modifiers.
abstract: Autophagy is an evolutionarily conserved degradation pathway characterized by dynamic rearrangement of membranes that sequester cytoplasm, protein aggregates, organelles, and pathogens for delivery to the vacuole and lysosome, respectively. The ability of autophagosomal membranes to act selectively toward specific cargo is dependent on the small ubiquitin-like modifier ATG8/LC3 and the LC3-interacting region (LIR) present in autophagy receptors. Here, we describe a comprehensive protein-protein interaction analysis of TBC (Tre2, Bub2, and Cdc16) domain-containing Rab GTPase-activating proteins (GAPs) as potential autophagy adaptors. We identified 14 TBC domain-containing Rab GAPs that bind directly to ATG8 modifiers and that colocalize with LC3-positive autophagy membranes in cells. Intriguingly, one of our screening hits, TBC1D5, contains two LIR motifs. The N-terminal LIR was critical for interaction with the retromer complex and transport of cargo. Direct binding of the retromer component VPS29 to TBC1D5 could be titrated out by LC3, indicating a molecular switch between endosomes and autophagy. Moreover, TBC1D5 could bridge the endosome and autophagosome via its C-terminal LIR motif. During starvation-induced autophagy, TBC1D5 was relocalized from endosomal localization to the LC3-positive autophagosomes. We propose that LC3-interacting Rab GAPs are implicated in the reprogramming of the endocytic trafficking events under starvation-induced autophagy.
authors.affiliation: Frankfurt Institute for Molecular Life Sciences and Institute of Biochemistry II, Goethe University School of Medicine, Frankfurt, Germany.
authors.forename: Doris
authors.initials: D
authors.lastname: Popovic
authors.forename: Masato
authors.initials: M
authors.lastname: Akutsu
authors.forename: Ivana
authors.initials: I
authors.lastname: Novak
authors.forename: J Wade
authors.initials: JW
authors.lastname: Harper
authors.forename: Christian
authors.initials: C
authors.lastname: Behrends
authors.forename: Ivan
authors.initials: I
authors.lastname: Dikic
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001343:Autophagy; D000071190:Autophagy-Related Protein 8 Family; D002460:Cell Line; D004705:Endocytosis; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D016415:Sequence Alignment; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000071190:Autophagy-Related Protein 8 Family; C498698:GABARAPL2 protein, human; D020690:GTPase-Activating Proteins; D008840:Microfilament Proteins; C543487:TBC1D5 protein, human; D020691:rab GTP-Binding Proteins