FIGURE 2:

Dissipation of mechanical work by stress fiber remodeling limits the traction forces applied on extracellular anchorages. Several sources of dissipation are schematized. The rolling tube represents the weak and fluctuating coupling of stress fiber (toilet paper) with the extracellular anchorages (the wall). It mimics the transient detachment of integrins (frictional slippage), as well as the disengagement of actin bundle from adhesions (clutch). Paper rolling out represents the nucleation of actin filaments by focal adhesions and filament translocation by myosins. Paper stretching represents the fiber elasticity and the energy that is lost in deforming it rather than pulling on the substrate. The character represents myosins at work, losing energy by pulling on a viscoelastic and ever-changing fiber and disassembling it in the meantime. (Drawing by “Benthos von Detritus,” http://benthos4.deviantart.com.)