Department for NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Faßberg 11, 37077, Göttingen, Germany.
Institute of Cellular and Molecular Immunology, Georg August University of Göttingen, Humboldtallee 34, 37073, Göttingen, Germany.
Nat Commun. 2020 Feb 12;11(1):848. doi: 10.1038/s41467-020-14544-1.
Antibody-mediated immune responses rely on antigen recognition by the B cell antigen receptor (BCR) and the proper engagement of its intracellular signal effector proteins. Src homology (SH) 2 domain-containing leukocyte protein of 65 kDa (SLP65) is the key scaffold protein mediating BCR signaling. In resting B cells, SLP65 colocalizes with Cbl-interacting protein of 85 kDa (CIN85) in cytoplasmic granules whose formation is not fully understood. Here we show that effective B cell activation requires tripartite phase separation of SLP65, CIN85, and lipid vesicles into droplets via vesicle binding of SLP65 and promiscuous interactions between nine SH3 domains of the trimeric CIN85 and the proline-rich motifs (PRMs) of SLP65. Vesicles are clustered and the dynamical structure of SLP65 persists in the droplet phase in vitro. Our results demonstrate that phase separation driven by concerted transient interactions between scaffold proteins and vesicles is a cellular mechanism to concentrate and organize signal transducers.
抗体介导的免疫反应依赖于 B 细胞抗原受体 (BCR) 对抗原的识别，以及其细胞内信号效应蛋白的正确结合。Src 同源 (SH) 2 结构域包含的白细胞蛋白 65kDa (SLP65) 是介导 BCR 信号的关键支架蛋白。在静止的 B 细胞中，SLP65 与 85kDa 的 Cbl 相互作用蛋白 (CIN85) 在细胞质颗粒中共定位，但其形成尚未完全了解。在这里，我们表明有效的 B 细胞激活需要 SLP65、CIN85 和脂质囊泡通过 SLP65 的囊泡结合和三聚体 CIN85 的九个 SH3 结构域与 SLP65 的富含脯氨酸基序 (PRM) 之间的混杂相互作用，三相分离成液滴。囊泡被聚集，并且 SLP65 的动态结构在体外的液滴相中持续存在。我们的结果表明，由支架蛋白和囊泡之间协调的瞬时相互作用驱动的相分离是一种浓缩和组织信号转导物的细胞机制。
