北京师范大学毛兰群团队报道了维生素C驱动肌动蛋白再转运相变——单泡电化学揭示的双相胞吐调节。相关研究成果于2024年6月18日发表在《美国化学会杂志》。

揭示主导蛋白质相动力学的分子机制是破解复杂的细胞内调节机制的迫切需要。虽然离子和生物大分子在调节蛋白质相分离方面已被广泛认可，但基本上构成胞质化学气氛的小分子对蛋白质相行为的影响很少被理解。

该文中，研究人员报道了一种维持还原性细胞内气氛的关键小分子维生素C（VC），驱动肌球蛋白II/F-肌动蛋白（肌动蛋白）细胞骨架的重入相变。肌动蛋白束在低VC状态下凝聚，在体外或神经元细胞内在高VC状态下聚集，通过伴随VC浓度单调增加的肌动蛋白II蛋白聚集-解离过程。

基于这一发现，研究人员采用原位单细胞和单囊泡电化学，来证明细胞内VC气氛对儿茶酚胺递质囊泡胞吐的定量调节，即胞吐释放量在低VC状态下增加，在高VC状态下减少。此外，还展示了VC如何通过肌动蛋白相变和细胞内游离钙水平，对膜张力的抵消或协同作用来调节细胞膜-囊泡融合孔动力学。

该工作揭示了基于小分子的可逆蛋白质相位调节机制，为化学神经调控和治疗范围的扩展铺平了新的道路。

附：英文原文

Title: Vitamin C Drives Reentrant Actin Phase Transition: Biphasic Exocytosis Regulation Revealed by Single-Vesicle Electrochemistry

Author: Jing Liu, Ying Jiang, Ran Liu, Jing Jin, Shiyi Wei, Wenliang Ji, Xiulan He, Fei Wu, Ping Yu, Lanqun Mao

Issue&Volume: June 18, 2024

Abstract: Unveiling molecular mechanisms that dominate protein phase dynamics has been a pressing need for deciphering the intricate intracellular modulation machinery. While ions and biomacromolecules have been widely recognized for modulating protein phase separations, effects of small molecules that essentially constitute the cytosolic chemical atmosphere on the protein phase behaviors are rarely understood. Herein, we report that vitamin C (VC), a key small molecule for maintaining a reductive intracellular atmosphere, drives reentrant phase transitions of myosin II/F-actin (actomyosin) cytoskeletons. The actomyosin bundle condensates dissemble in the low-VC regime and assemble in the high-VC regime in vitro or inside neuronal cells, through a concurrent myosin II protein aggregation–dissociation process with monotonic VC concentration increase. Based on this finding, we employ in situ single-cell and single-vesicle electrochemistry to demonstrate the quantitative modulation of catecholamine transmitter vesicle exocytosis by intracellular VC atmosphere, i.e., exocytotic release amount increases in the low-VC regime and decreases in the high-VC regime. Furthermore, we show how VC regulates cytomembrane-vesicle fusion pore dynamics through counteractive or synergistic effects of actomyosin phase transitions and the intracellular free calcium level on membrane tensions. Our work uncovers the small molecule-based reversive protein phase regulatory mechanism, paving a new way to chemical neuromodulation and therapeutic repertoire expansion.

DOI: 10.1021/jacs.4c02710

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c02710