State Key Laboratory of Chemical Biology, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China.
Proc Natl Acad Sci U S A. 2024 Mar 12;121(11):e2315550121. doi: 10.1073/pnas.2315550121. Epub 2024 Mar 4.
TAX1BP1, a multifunctional autophagy adaptor, plays critical roles in different autophagy processes. As an autophagy receptor, TAX1BP1 can interact with RB1CC1, NAP1, and mammalian ATG8 family proteins to drive selective autophagy for relevant substrates. However, the mechanistic bases underpinning the specific interactions of TAX1BP1 with RB1CC1 and mammalian ATG8 family proteins remain elusive. Here, we find that there are two distinct binding sites between TAX1BP1 and RB1CC1. In addition to the previously reported TAX1BP1 SKICH (skeletal muscle and kidney enriched inositol phosphatase (SKIP) carboxyl homology)/RB1CC1 coiled-coil interaction, the first coiled-coil domain of TAX1BP1 can directly bind to the extreme C-terminal coiled-coil and Claw region of RB1CC1. We determine the crystal structure of the TAX1BP1 SKICH/RB1CC1 coiled-coil complex and unravel the detailed binding mechanism of TAX1BP1 SKICH with RB1CC1. Moreover, we demonstrate that RB1CC1 and NAP1 are competitive in binding to the TAX1BP1 SKICH domain, but the presence of NAP1's FIP200-interacting region (FIR) motif can stabilize the ternary TAX1BP1/NAP1/RB1CC1 complex formation. Finally, we elucidate the molecular mechanism governing the selective interactions of TAX1BP1 with ATG8 family members by solving the structure of GABARAP in complex with the non-canonical LIR (LC3-interacting region) motif of TAX1BP1, which unveils a unique binding mode between LIR and ATG8 family protein. Collectively, our findings provide mechanistic insights into the interactions of TAX1BP1 with RB1CC1 and mammalian ATG8 family proteins and are valuable for further understanding the working mode and function of TAX1BP1 in autophagy.
TAX1BP1 是一种多功能自噬衔接蛋白，在不同的自噬过程中发挥关键作用。作为自噬受体，TAX1BP1 可以与 RB1CC1、NAP1 和哺乳动物 ATG8 家族蛋白相互作用，以驱动相关底物的选择性自噬。然而，TAX1BP1 与 RB1CC1 和哺乳动物 ATG8 家族蛋白特异性相互作用的机制基础仍不清楚。在这里，我们发现 TAX1BP1 与 RB1CC1 之间存在两个不同的结合位点。除了先前报道的 TAX1BP1 SKICH（骨骼肌和肾脏富含肌醇磷酸酶 SKIP 的羧基结构域）/RB1CC1 卷曲螺旋相互作用外，TAX1BP1 的第一个卷曲螺旋结构域可以直接与 RB1CC1 的极端 C 端卷曲螺旋和爪区结合。我们确定了 TAX1BP1 SKICH/RB1CC1 卷曲螺旋复合物的晶体结构，并揭示了 TAX1BP1 SKICH 与 RB1CC1 详细的结合机制。此外，我们证明 RB1CC1 和 NAP1 竞争结合 TAX1BP1 SKICH 结构域，但 NAP1 的 FIP200 相互作用区（FIR）基序的存在可以稳定 TAX1BP1/NAP1/RB1CC1 三元复合物的形成。最后，我们通过解析与 TAX1BP1 的非典型 LIR（LC3 相互作用区）基序结合的 GABARAP 结构，阐明了 TAX1BP1 与 ATG8 家族成员选择性相互作用的分子机制，揭示了 LIR 与 ATG8 家族蛋白之间独特的结合模式。总之，我们的研究结果为 TAX1BP1 与 RB1CC1 和哺乳动物 ATG8 家族蛋白相互作用提供了机制见解，对进一步了解 TAX1BP1 在自噬中的工作模式和功能具有重要价值。
