Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104.
Max Delbrück Institute for Molecular Medicine, Berlin Institute for Medical Systems Biology, Berlin 10115, Germany.
Mol Biol Cell. 2023 Dec 1;34(13):br21. doi: 10.1091/mbc.E22-11-0496. Epub 2023 Sep 20.
The aggregation of the disordered neuronal protein, α-Synuclein (αS), is the primary pathological feature of Parkinson's disease. Current hypotheses favor cell-to-cell spread of αS species as underlying disease progression, driving interest in identifying the molecular species and cellular processes involved in cellular internalization of αS. Prior work from our lab identified the chemically specific interaction between αS and the presynaptic adhesion protein neurexin-1β (N1β) to be capable of driving cellular internalization of both monomer and aggregated forms of αS. Here we explore the physical basis of N1β-driven internalization of αS. Specifically, we show that spontaneous internalization of αS by SH-SY5Y and HEK293 cells expressing N1β requires essentially all of the membrane-binding domain of αS; αS constructs truncated beyond residue 90 bind to N1β in the plasma membrane of HEK cells, but are not internalized. Interestingly, before internalization, αS and N1β codiffuse rapidly in the plasma membrane. αS constructs that are not internalized show very slow mobility themselves, as well as slow N1β diffusion. Finally, we find that truncated αS is capable of blocking internalization of full-length αS. Our results draw attention to the potential therapeutic value of blocking αS-N1β interactions.
α-突触核蛋白（αS）的无序神经元蛋白聚集是帕金森病的主要病理特征。目前的假说倾向于认为 αS 物种的细胞间传播是疾病进展的基础，这促使人们关注鉴定参与 αS 细胞内化的分子物种和细胞过程。我们实验室之前的工作确定了 αS 与突触前粘附蛋白神经连接蛋白-1β（N1β）之间的化学特异性相互作用，能够驱动单体和聚集形式的 αS 的细胞内化。在这里，我们探讨了 N1β 驱动 αS 内化的物理基础。具体来说，我们表明，表达 N1β 的 SH-SY5Y 和 HEK293 细胞的自发内化需要 αS 的基本上所有膜结合结构域；在 HEK 细胞的质膜中，截断至 90 位残基以下的 αS 构建体与 N1β 结合，但不被内化。有趣的是，在内化之前，αS 和 N1β 在质膜中迅速共扩散。不能内化的 αS 构建体本身的迁移率非常慢，N1β 的扩散也很慢。最后，我们发现截断的 αS 能够阻止全长 αS 的内化。我们的结果提请注意阻断 αS-N1β 相互作用的潜在治疗价值。
