How caffeine modulates actin filament assembly dynamics

Sydney Paulin^1,2,3, Ellen Hyeran Kang^1,2,4,5

1:University of Central Florida, 2:Nanoscience Technology Center, 3:College of Undergraduate Studies, 4:Department of Physics, 5:Department of Materials Science and Engineering

The assembly dynamics of actin, an essential cytoskeletal protein, play an important role in numerous cellular processes including cell movement and force generation, providing cells with mechanical and structural support. Various cytoskeletal drugs have been shown to alter actin filament assembly and disassembly by binding to actin. Caffeine is a naturally occurring drug found in many plants and various nuts. Previous studies have shown caffeine releases internally stored Ca²⁺ and relaxes smooth muscle through actin depolymerization. However, how caffeine affects actin assembly dynamics has not been well understood. The goal of this study is to determine the effects of caffeine on actin polymerization kinetics at varying concentrations.  We utilized pyrene fluorescence assays to evaluate time course of actin filament assembly kinetics in the presence of caffeine. Total Internal Reflection Fluorescence (TIRF) microscopy imaging allowed us to directly visualize the assembly as well as disassembly of individual actin filaments in real time. Our preliminary data shows that varying concentrations of caffeine have opposing effects on actin filament assembly dynamics. This study can help us understand the effects of caffeine on the actin cytoskeleton assembly/disassembly dynamics.