PDF(Pubmed)
Abstract：
Vesicular transport relies on multimeric trafficking complexes to capture cargo and drive vesicle budding and fusion. Faithful assembly of the trafficking complexes is essential to their functions but remains largely unexplored. Assembly of AP2 adaptor, a heterotetrameric protein complex regulating clathrin-mediated endocytosis, is assisted by the chaperone AAGAB. Here, we found that AAGAB initiates AP2 assembly by stabilizing its α and σ2 subunits, but the AAGAB:α:σ2 complex cannot recruit additional AP2 subunits. We identified CCDC32 as another chaperone regulating AP2 assembly. CCDC32 recognizes the AAGAB:α:σ2 complex, and its binding leads to the formation of an α:σ2:CCDC32 ternary complex. The α:σ2:CCDC32 complex serves as a template that sequentially recruits the µ2 and β2 subunits of AP2 to complete AP2 assembly, accompanied by CCDC32 release. The AP2-regulating function of CCDC32 is disrupted by a disease-causing mutation. These findings demonstrate that AP2 is assembled by a handover mechanism switching from AAGAB-based initiation complexes to CCDC32-based template complexes. A similar mechanism may govern the assembly of other trafficking complexes exhibiting the same configuration as AP2.
摘要：
囊泡运输依靠多聚体运输复合物来捕获货物并驱动囊泡出芽和融合。忠实地组装贩运综合体对其功能至关重要，但仍未得到探索。AP2适配器的组装，调节网格蛋白介导的内吞作用的异源四聚体蛋白复合物，由监护人AAGAB协助。这里,我们发现AAGAB通过稳定其α和σ2亚基来启动AP2组装，但是AAGAB：α：σ2复合物不能募集额外的AP2亚基。我们将CCDC32鉴定为调节AP2组装的另一种伴侣。CCDC32识别AAGAB：α：σ2复合物，其结合导致形成α：σ2：CCDC32三元复合物。α：σ2：CCDC32复合物充当模板，依次募集AP2的µ2和β2亚基以完成AP2组装，伴随着CCDC32发布。CCDC32的AP2调节功能被致病突变破坏。这些发现表明，AP2是通过从基于AAGAB的起始复合物切换到基于CCDC32的模板复合物的切换机制组装的。类似的机制可以控制显示与AP2相同构型的其他运输复合物的组装。
