DataSheet1_Actin Bundle Nanomechanics and Organization Are Modulated by Macromolecular Crowding and Electrostatic Interactions.DOCX

The structural and mechanical properties of actin bundles are essential to eukaryotic cells, aiding in cell motility and mechanical support of the plasma membrane. Bundle formation occurs in crowded intracellular environments composed of various ions and macromolecules. Although the roles of cations and macromolecular crowding in the mechanics and organization of actin bundles have been independently established, how changing both intracellular environmental conditions influence bundle mechanics at the nanoscale has yet to be established. Here we investigate how electrostatics and depletion interactions modulate the relative Young’s modulus and height of actin bundles using atomic force microscopy. Our results demonstrate that cation- and depletion-induced bundles display an overall reduction of relative Young’s modulus depending on either cation or crowding concentrations. Furthermore, we directly measure changes to cation- and depletion-induced bundle height, indicating that bundles experience alterations to filament packing supporting the reduction to relative Young’s modulus. Taken together, our work suggests that electrostatic and depletion interactions may act counteractively, impacting actin bundle nanomechanics and organization.

肌动蛋白束的结构和力学特性对于真核细胞至关重要，其在细胞运动和质膜机械支持中发挥着关键作用。肌动蛋白束的形成发生在充满各种离子和宏分子的大致胞质环境中。尽管阳离子和宏分子拥挤在肌动蛋白束的力学和组织结构中的作用已被独立确立，但尚无定论的是，细胞内环境条件的变化如何影响纳米尺度上肌动蛋白束的力学特性。在本研究中，我们通过原子力显微镜调查了静电和耗竭相互作用如何调节肌动蛋白束的相对杨氏模量和高度。我们的结果表明，阳离子和耗竭诱导的束表现出相对杨氏模量的总体降低，这取决于阳离子或拥挤浓度。此外，我们直接测量了阳离子和耗竭诱导的束高度的变化，表明肌动蛋白束经历了改变，以支持相对杨氏模量的降低。综合来看，我们的研究表明，静电和耗竭相互作用可能具有拮抗作用，影响肌动蛋白束的纳米力学和组织结构。