Pierre Recho — Page 2

arXiv2013

Mechanotaxis and cell motility

We propose a mechanism of cell motility which is based on contraction and does not require protrusion. The contraction driven translocation of a cell is due to internal flow of the cytoskeleton generated by molecular motors. Each motor contributes to the stress field and simultaneously undergoes biased random motion in the direction of a higher value of this stress. In this way active cross-linkers use passive actin network as a medium through which they interact and self-organize. The model exhibits motility initiation pattern similar to the one observed in experiments on keratocytes.

physics.bio-ph↗

arXiv2013

An asymmetry between pushing and pulling for crawling cells

Eukaryotic cells possess motility mechanisms allowing them not only to self-propel but also to exert forces on obstacles (to push) and to carry cargoes (to pull). To study the inherent asymmetry between active pushing and pulling we model a crawling acto-myosin cell extract as a 1D layer of active gel subjected to external forces. We show that pushing is controlled by protrusion and that the macroscopic signature of the protrusion dominated motility mechanism is concavity of the force velocity relation. Instead, pulling is driven by protrusion only at small values of the pulling force and it is replaced by contraction when the pulling force is sufficiently large. This leads to more complex convex-concave structure of the force velocity relation, in particular, competition between protrusion and contraction can produce negative mobility in a biologically relevant range. The model illustrates active readjustment of the force generating machinery in response to changes in the dipole structure of external forces. The possibility of switching between complementary active mechanisms implies that if necessary 'pushers' can replace 'pullers' and visa versa.

physics.bio-ph↗