Madasu Yadaiah, Yang Changsong, Boczkowska Malgorzata, Bethoney Kelley A, Zwolak Adam, Rebowski Grzegorz, Svitkina Tatyana, Dominguez Roberto
Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
Department of Biology, University of Pennsylvania, Philadelphia, PA 19104.
Mol Biol Cell. 2015 Apr 1;26(7):1308-22. doi: 10.1091/mbc.E14-10-1448. Epub 2015 Feb 5.
PICK1 is a modular scaffold implicated in synaptic receptor trafficking. It features a PDZ domain, a BAR domain, and an acidic C-terminal tail (ACT). Analysis by small- angle x-ray scattering suggests a structural model that places the receptor-binding site of the PDZ domain and membrane-binding surfaces of the BAR and PDZ domains adjacent to each other on the concave side of the banana-shaped PICK1 dimer. In the model, the ACT of one subunit of the dimer interacts with the PDZ and BAR domains of the other subunit, possibly accounting for autoinhibition. Consistently, full-length PICK1 shows diffuse cytoplasmic localization, but it clusters on vesicle-like structures that colocalize with the trans-Golgi network marker TGN38 upon deletion of either the ACT or PDZ domain. This localization is driven by the BAR domain. Live-cell imaging further reveals that PICK1-associated vesicles undergo fast, nondirectional motility in an F-actin-dependent manner, but deleting the ACT dramatically reduces vesicle speed. Thus the ACT links PICK1-associated vesicles to a motility factor, likely myosin, but, contrary to previous reports, PICK1 neither binds nor inhibits Arp2/3 complex.
PICK1是一种参与突触受体运输的模块化支架蛋白。它具有一个PDZ结构域、一个BAR结构域和一个酸性C末端尾巴（ACT）。小角X射线散射分析表明，其结构模型显示PDZ结构域的受体结合位点以及BAR和PDZ结构域的膜结合表面在香蕉形PICK1二聚体的凹面彼此相邻。在该模型中，二聚体一个亚基的ACT与另一个亚基的PDZ和BAR结构域相互作用，这可能是自抑制的原因。一致的是，全长PICK1呈弥漫性细胞质定位，但在缺失ACT或PDZ结构域后，它会聚集在与反式高尔基体网络标记物TGN38共定位的囊泡样结构上。这种定位是由BAR结构域驱动的。活细胞成像进一步揭示，与PICK1相关的囊泡以F-肌动蛋白依赖的方式进行快速、无定向运动，但缺失ACT会显著降低囊泡速度。因此，ACT将与PICK1相关的囊泡与一种运动因子（可能是肌球蛋白）联系起来，但与之前的报道相反，PICK1既不结合也不抑制Arp2/3复合体。
