Direct measurements of interactions between intermediate filaments*

The cytoskeleton consists of F-actin, microtublues and intermediate filaments (IFs), which together form a complex composite network. This composite network provides stability and flexibility for cells and enables them to adapt to a variety of external conditions. F-actin and microtubule networks have been studied extensively and a large number of different cross-linkers are known. By contrast, the interactions within reconstituted IF networks are less well understood. Microrheological measurements on vimentin networks reveal slow network dynamics, and allow us to separate the filament and network formation time scales. By amplifying electrostatic attractions or diminishing hydrophobic interactions between filaments, we are able to study the impact of the respective effect on intra- and inter-filament interactions. Combining optical trapping and fluorescence microscopy enables us to bring two single vimentin IFs in contact and directly study the interactions between them. These results, in combination with studies of the mechanical properties of single IFs, allow us to model the interactions with Monte-Carlo simulations, thereby gaining a deeper understanding of cytoskeletal structures.