Physical Approaches for Probing the Mechanical Properties of Intermediate Filaments

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Abstract Cell must support forces, must exert forces, and must respond to forces. All these behaviors are fundamentally built on mechanical properties of the cells, which are largely determined by three filamentous networks within the cytoskeleton, actin, microtubules, and intermediate filaments (IF). While actin and microtubules are widely cited as the crucial components determining the mechanical properties of the cells and are well studied, the importance of intermediate filaments is increasingly being recognized. For example, cells without vimentin intermediate filaments are much weaker and more susceptible to break up upon application of small shear forces comparable in magnitude to those encountered in blood flow; moreover, they are much less stable, with the nucleus and organelles lacking positional stability and being easier to move. The presence of vimentin IF networks mechanically stabilize cells; however, they must work in concert with the other filamentous networks. The overarching goal of this Program Project is to elucidate the roles of the vimentin IF network and how it operates in concert with other filamentous networks to determine the mechanical properties of cells. We will accomplish this through studies of reconstituted mixed networks with and without motor proteins to isolate the mechanics of the IF networks in the presence of the other networks. The results of these studies will be compared to the mechanical behavior of cells grown on flat substrates, both isolated and in confluent layers, and for cells from vimentin-related diseases. Ultimately, we will build new systems to enable studies of the properties of cells grown in three-dimensional networks that mimic environments in vivo. The knowledge gained in this study will establish foundational scientific understanding of roles of vimentin IFs in cell mechanics, which will ultimately provide guidance to the development of treatments for vimentin related diseases.