Force-driven polymerization in cells: Actin filaments and focal adhesions

We describe a thermodynamic principle determining the phenomenon of protein self-assembly controlled by elastic stresses. This principle is based on the Gibbs-Dühem-like relationship between the chemical potential of the aggregated molecules and the stresses produced by forces acting on a protein aggregate. We present two biological systems whose operation can be driven by this principle: actin filament, a polymerizing processive capping by proteins of the formin family, and focal adhesions mediating a mechanical link between the cytoskeleton and extracellular substrates. We describe the major phenomenology of these systems and overview recent models, aimed at understanding the mechanisms of their functioning.