INTERRELATIONSHIP BETWEEN CONTRACTILITY AND DYNAMICS OF ACTOMYOSIN SYSTEM IN NON-MUSCLE CELLS

Abstract

Contractile actomyosin systems in non-muscle cells are essential for a variety of cellular processes including adhesion and morphogenesis. However, how actin dynamics (in particular, incorporation-dissociation driven flow along the fibers) and myosin dependent contractility are related to each other in matured ventral stress fibers (VSFs) still remains elusive. To this end, I manipulated either actin incorporation or forces to investigate their effects. Surprisingly, SMIFH2 strongly inhibited the force exertion. I hence proposed that formins could physically link actin filaments with each other, thus participating in force transmission processes. On the other hand, drug inhibition of myosin prevented actin incorporation along VSFs. Furthermore, stretching rescued inhibited actin incorporation in formin- but not in myosin-inhibited cells. Therefore, I hypothesized that myosin activities are necessary for actin incorporation in VSF. Our results revealed that VSFs are dynamic viscoelastic systems, in which myosin driven contractility and actin dynamics are fine-tuned with each other.