North Brian J, Ohnstad Amelia E, Ragusa Michael J, Shoemaker Christopher J
Department of Biochemistry and Cell Biology, Geisel School of Medicine, Dartmouth College, Hanover, NH, USA.
Department of Physiology, Biophysics, and Systems Biology, Weill Cornell Medicine, New York, NY, USA.
J Cell Biol. 2025 Apr 7;224(4). doi: 10.1083/jcb.202407105. Epub 2025 Feb 10.
During autophagy, toxic cargo is encapsulated by autophagosomes and trafficked to lysosomes for degradation. NBR1, an autophagy receptor targeting ubiquitinated aggregates, serves as a model for studying the multivalent, heterotypic interactions of cargo-bound receptors. Here, we find that three critical NBR1 partners-ATG8-family proteins, FIP200, and TAX1BP1-each bind to distinct, overlapping determinants within a short linear interaction motif (SLiM). To explore whether overlapping SLiMs extend beyond NBR1, we analyzed >100 LC3-interacting regions (LIRs), revealing that FIP200 and/or TAX1BP1 binding to LIRs is a common phenomenon and suggesting LIRs as protein interaction hotspots. Phosphomimetic peptides demonstrate that phosphorylation generally enhances FIP200 and ATG8-family binding but not TAX1BP1, indicating differential regulation. In vivo, LIR-mediated interactions with TAX1BP1 promote optimal NBR1 flux by leveraging additional functionalities from TAX1BP1. These findings reveal a one-to-many binding modality in the LIR motif of NBR1, illustrating the cooperative mechanisms of autophagy receptors and the regulatory potential of multifunctional SLiMs.
在自噬过程中，有毒物质被自噬体包裹，并运输到溶酶体进行降解。NBR1是一种靶向泛素化聚集体的自噬受体，可作为研究货物结合受体的多价、异型相互作用的模型。在这里，我们发现NBR1的三个关键伙伴——ATG8家族蛋白、FIP200和TAX1BP1——各自结合短线性相互作用基序（SLiM）内不同但重叠的决定簇。为了探究重叠的SLiM是否超出NBR1的范围，我们分析了100多个LC3相互作用区域（LIR），发现FIP200和/或TAX1BP1与LIR的结合是一种常见现象，并表明LIR是蛋白质相互作用热点。模拟磷酸化的肽段表明，磷酸化通常会增强FIP200和ATG8家族的结合，但不会增强TAX1BP1的结合，这表明存在差异调节。在体内，LIR介导的与TAX1BP1的相互作用通过利用TAX1BP1的其他功能促进最佳的NBR1通量。这些发现揭示了NBR1的LIR基序中的一对多结合模式，阐明了自噬受体的协同机制以及多功能SLiM的调节潜力。
