title: Modulation of serines 17 and 24 in the LC3-interacting region of Bnip3 determines pro-survival mitophagy versus apoptosis.
abstract: BH3-only proteins integrate apoptosis and autophagy pathways, yet regulation and functional consequences of pathway cross-talk are not fully resolved. The BH3-only protein Bnip3 is an autophagy receptor that signals autophagic degradation of mitochondria (mitophagy) via interaction of its LC3-interacting region (LIR) with Atg8 proteins. Here we report that phosphorylation of serine residues 17 and 24 flanking the Bnip3 LIR promotes binding to specific Atg8 members LC3B and GATE-16. Using quantitative multispectral image-based flow cytometry, we demonstrate that enhancing Bnip3-Atg8 interactions via phosphorylation-mimicked LIR mutations increased mitochondrial sequestration, lysosomal delivery, and degradation. Importantly, mitochondria were targeted by mitophagy prior to cytochrome c release, resulting in reduced cellular cytochrome c release capacity. Intriguingly, pro-survival Bcl-x(L) positively regulated Bnip3 binding to LC3B, sequestration, and mitochondrial autophagy, further supporting an anti-apoptotic role for Bnip3-induced mitophagy. The ensemble of these results demonstrates that the phosphorylation state of the Bnip3 LIR signals either the induction of apoptosis or pro-survival mitophagy.
authors.affiliation: Systems Biology of Cell Death Mechanisms, German Cancer Research Center (DKFZ), Bioquant, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zhu
authors.forename: Stefan
authors.initials: S
authors.lastname: Massen
authors.forename: Marco
authors.initials: M
authors.lastname: Terenzio
authors.forename: Verena
authors.initials: V
authors.lastname: Lang
authors.forename: Silu
authors.initials: S
authors.lastname: Chen-Lindner
authors.forename: Roland
authors.initials: R
authors.lastname: Eils
authors.forename: Ivana
authors.initials: I
authors.lastname: Novak
authors.forename: Ivan
authors.initials: I
authors.lastname: Dikic
authors.forename: Anne
authors.initials: A
authors.lastname: Hamacher-Brady
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Brady
mesh_terms: D017209:Apoptosis; D001483:Base Sequence; D002460:Cell Line; D002470:Cell Survival; D017931:DNA Primers; D005434:Flow Cytometry; D006801:Humans; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D063306:Mitophagy; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D012694:Serine / Q000378:metabolism*
chemical_list: C090121:BNIP3 protein, human; D017931:DNA Primers; C477012:MAP1LC3A protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D011518:Proto-Oncogene Proteins; D012694:Serine