School of Medicine, University of Split, Split, Croatia.
Faculty of Science, University of Split, Split, Croatia.
Autophagy. 2021 May;17(5):1232-1243. doi: 10.1080/15548627.2020.1755120. Epub 2020 Apr 24.
Mitophagy is a conserved intracellular catabolic process responsible for the selective removal of dysfunctional or superfluous mitochondria to maintain mitochondrial quality and need in cells. Here, we examine the mechanisms of receptor-mediated mitophagy activation, with the focus on BNIP3L/NIX mitophagy receptor, proven to be indispensable for selective removal of mitochondria during the terminal differentiation of reticulocytes. The molecular mechanisms of selecting damaged mitochondria from healthy ones are still very obscure. We investigated BNIP3L dimerization as a potentially novel molecular mechanism underlying BNIP3L-dependent mitophagy. Forming stable homodimers, BNIP3L recruits autophagosomes more robustly than its monomeric form. Amino acid substitutions of key transmembrane residues of BNIP3L, BNIP3L or BNIP3L, led to the abolishment of dimer formation, resulting in the lower LC3A-BNIP3L recognition and subsequently lower mitophagy induction. Moreover, we identified the serine 212 as the main amino acid residue at the C-terminal of BNIP3L, which extends to the intermembrane space, responsible for dimerization. In accordance, the phosphomimetic mutation BNIP3L leads to a complete loss of BNIP3L dimerization. Thus, the interplay between BNIP3L phosphorylation and dimerization indicates that the combined mechanism of LIR phosphorylation and receptor dimerization is needed for proper BNIP3L-dependent mitophagy initiation and progression. AMBRA1: autophagy and beclin 1 regulator 1; Baf A1: bafilomycin A; BH3: BCL2 homology 3; BNIP3: BCL2 interacting protein 3; BNIP3L/NIX: BCL2 interacting protein 3 like; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; CoCl: cobalt (II) chloride; FKBP8: FKBP prolyl isomerase 8; FUNDC1: FUN14 domain containing 1; GABARAP: GABA type A receptor-associated protein; GST: glutathione S-transferase; IMM: inner mitochondrial membrane; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; OMM: outer mitochondrial membrane; PHB2: prohibitin 2; PI: propidium iodide; PINK1: PTEN induced kinase 1; TM: transmembrane domain; TOMM20: translocase of outer mitochondrial membrane 20.
自噬是一种保守的细胞内分解代谢过程，负责选择性去除功能失调或多余的线粒体，以维持细胞内线粒体的质量和需求。在这里，我们研究了受体介导的自噬激活的机制，重点是 BNIP3L/NIX 自噬受体，该受体被证明在网织红细胞的终末分化过程中对于选择性去除线粒体是必不可少的。从健康的线粒体中选择受损线粒体的分子机制仍然非常模糊。我们研究了 BNIP3L 二聚化作为 BNIP3L 依赖性自噬的潜在新分子机制。BNIP3L 形成稳定的同源二聚体，比其单体形式更有效地募集自噬体。BNIP3L 的关键跨膜残基的氨基酸取代，BNIP3L 或 BNIP3L，导致二聚体形成的消除，导致较低的 LC3A-BNIP3L 识别，随后较低的自噬诱导。此外，我们确定 BNIP3L 的 C 末端丝氨酸 212 是 BNIP3L 延伸到膜间空间的主要氨基酸残基，负责二聚化。相应地，磷酸化模拟突变 BNIP3L 导致 BNIP3L 二聚化的完全丧失。因此，BNIP3L 磷酸化和二聚化之间的相互作用表明，LIR 磷酸化和受体二聚化的组合机制对于适当的 BNIP3L 依赖性自噬起始和进展是必要的。AMBRA1：自噬和 beclin 1 调节因子 1；Baf A1：巴弗霉素 A；BH3：BCL2 同源性 3；BNIP3：BCL2 相互作用蛋白 3；BNIP3L/NIX：BCL2 相互作用蛋白 3 样；CCCP：羰基氰化物 3-氯苯腙；CoCl：氯化钴；FKBP8：FKBP 脯氨酰异构酶 8；FUNDC1：FUN14 结构域包含 1；GABARAP：GABA 型 A 受体相关蛋白；GST：谷胱甘肽 S-转移酶；IMM：内线粒体膜；LIR：LC3 相互作用区域；MAP1LC3/LC3：微管相关蛋白 1 轻链 3；OMM：外线粒体膜；PHB2：抑制素 2；PI：碘化丙啶；PINK1：PTEN 诱导的激酶 1；TM：跨膜域；TOMM20：外线粒体膜转运蛋白 20。
