Molecular Cell Biology of Autophagy, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK; Department of Cell and Chemical Biology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC Leiden, the Netherlands(‡).
Structural Biology Science Technology Platforms, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
J Mol Biol. 2021 Jun 25;433(13):166987. doi: 10.1016/j.jmb.2021.166987. Epub 2021 Apr 24.
Autophagy is a highly conserved degradative pathway, essential for cellular homeostasis and implicated in diseases including cancer and neurodegeneration. Autophagy-related 8 (ATG8) proteins play a central role in autophagosome formation and selective delivery of cytoplasmic cargo to lysosomes by recruiting autophagy adaptors and receptors. The LC3-interacting region (LIR) docking site (LDS) of ATG8 proteins binds to LIR motifs present in autophagy adaptors and receptors. LIR-ATG8 interactions can be highly selective for specific mammalian ATG8 family members (LC3A-C, GABARAP, and GABARAPL1-2) and how this specificity is generated and regulated is incompletely understood. We have identified a LIR motif in the Golgi protein SCOC (short coiled-coil protein) exhibiting strong binding to GABARAP, GABARAPL1, LC3A and LC3C. The residues within and surrounding the core LIR motif of the SCOC LIR domain were phosphorylated by autophagy-related kinases (ULK1-3, TBK1) increasing specifically LC3 family binding. More distant flanking residues also contributed to ATG8 binding. Loss of these residues was compensated by phosphorylation of serine residues immediately adjacent to the core LIR motif, indicating that the interactions of the flanking LIR regions with the LDS are important and highly dynamic. Our comprehensive structural, biophysical and biochemical analyses support and provide novel mechanistic insights into how phosphorylation of LIR domain residues regulates the affinity and binding specificity of ATG8 proteins towards autophagy adaptors and receptors.
自噬是一种高度保守的降解途径，对细胞稳态至关重要，与癌症和神经退行性疾病等疾病有关。自噬相关 8（ATG8）蛋白在自噬体形成和通过招募自噬衔接子和受体将细胞质货物选择性递送至溶酶体中发挥核心作用。ATG8 蛋白的 LC3 相互作用区域（LIR）对接位点（LDS）与自噬衔接子和受体中存在的 LIR 基序结合。LIR-ATG8 相互作用对特定的哺乳动物 ATG8 家族成员（LC3A-C、GABARAP 和 GABARAPL1-2）具有高度选择性，而这种特异性是如何产生和调节的尚不完全清楚。我们已经确定了高尔基蛋白 SCOC（短卷曲螺旋蛋白）中的一个 LIR 基序，该基序与 GABARAP、GABARAPL1、LC3A 和 LC3C 具有很强的结合能力。SCOC LIR 结构域内和周围核心 LIR 基序的残基被自噬相关激酶（ULK1-3、TBK1）磷酸化，特异性增加 LC3 家族结合。更远的侧翼残基也有助于 ATG8 结合。这些残基的缺失被紧邻核心 LIR 基序的丝氨酸残基的磷酸化所补偿，表明侧翼 LIR 区域与 LDS 的相互作用很重要且高度动态。我们的综合结构、生物物理和生化分析支持并提供了新的机制见解，说明了 LIR 结构域残基的磷酸化如何调节 ATG8 蛋白与自噬衔接子和受体的亲和力和结合特异性。
