The cytoskeletal protein actin forms a spatially organized biopolymer network that plays a central role in many cellular processes. Actin filaments continuously assemble and disassemble, enabling cells to rapidly reorganize their cytoskeleton. Filament severing accelerates actin turnover, as both polymerization and depolymerization rates depend on the number of free filament ends — which severing increases. Here, we use light to control actin severing in vitro by locally generating reactive oxygen species (ROS) with photosensitive molecules such as fluorophores. We see that ROS sever actin filaments, which increases actin polymerization in our experiments. However, beyond a certain threshold, excessive severing leads to the disassembly of actin networks. Our experimental data is supported by simulations using a kinetic model of actin polymerization, which helps us understand the underlying dynamics. In cells, ROS are known to regulate the actin cytoskeleton, but the molecular mechanisms are poorly understood. Here we show that, in vitro, ROS directly affect actin reorganization.
Thomas Litschel is a postdoctoral fellow in the lab of David Weitz at Harvard University’s School of Engineering and Applied Sciences. He earned his PhD from the Max Planck Institute of Biochemistry in Germany, where he worked in the lab of Petra Schwille on bottom-up synthetic biology. Prior to that, he received his Master’s degree from Brandeis University, where he worked with Seth Fraden on chemical oscillators. He completed his undergraduate studies at Goethe University Frankfurt in Germany.