Hancock Lewis P, Allwood Ellen G, Palmer John S, Ayscough Kathryn R, Williamson Mike P
School of Biosciences, University of Sheffield, Sheffield, S10 2TN, UK.
Sci Rep. 2025 Aug 7;15(1):28951. doi: 10.1038/s41598-025-14248-w.
Endocytosis is critical. Its complexity means that many aspects remain poorly understood. We have developed an agent-based model covering key components of actin filament generation in endocytosis in Saccharomyces cerevisiae. The model incorporates realistic values for rates, affinities, concentrations, and mobilities, and reproduces essential features of endocytosis, from the arrival of WASp/Las17 and its inhibitor Sla1 at the membrane up to the burst of actin polymerisation. The model yields relative rates and affinities for interactions that cannot be measured experimentally, and places limitations on plausible scenarios. Specifically, it reveals three novel findings. First, Las17 must form multimeric complexes. Second, de novo F-actin nucleation occurs in two stages, involving the slow formation of linear trimers, followed by rapid polymerisation once an additional actin monomer is positioned at the side of the aligned monomers. Third, competition between SH3 domains and other factors, including actin, is critical to ensure on/off switching. This requires: (1) tandem domains binding to adjacent polyproline sites outcompeting single domains; (2) these tandem domains being weakened in overall affinity through a reduction in avidity by competition with single SH3 domains. We conclude with a pathway that proposes how controlled actin polymerisation occurs, and raises implications for further testing.
内吞作用至关重要。其复杂性意味着许多方面仍未得到充分理解。我们开发了一种基于代理的模型，涵盖酿酒酵母内吞作用中肌动蛋白丝生成的关键组件。该模型纳入了速率、亲和力、浓度和迁移率的实际值，并再现了内吞作用的基本特征，从WASp/Las17及其抑制剂Sla1到达膜表面直至肌动蛋白聚合爆发。该模型得出了无法通过实验测量的相互作用的相对速率和亲和力，并对合理的情况设置了限制。具体而言，它揭示了三个新发现。第一，Las17必须形成多聚体复合物。第二，新生F-肌动蛋白成核分两个阶段进行，包括线性三聚体的缓慢形成，然后一旦另一个肌动蛋白单体位于对齐单体的一侧，就会快速聚合。第三，SH3结构域与包括肌动蛋白在内的其他因素之间的竞争对于确保开关的开启和关闭至关重要。这需要：（1）与相邻多脯氨酸位点结合的串联结构域胜过单个结构域；（2）这些串联结构域通过与单个SH3结构域竞争而导致亲和力降低，从而削弱整体亲和力。我们最后提出了一条途径，该途径提出了受控肌动蛋白聚合如何发生，并对进一步测试具有启示意义。
