  Cortical actin networks are highly dynamic and play critical roles in shaping
the mechanical properties of cells. The actin cytoskeleton undergoes
significant reorganization over the course of the cell cycle, when cortical
actin transitions between open patched meshworks, homogeneous distributions,
and aligned bundles. Several types of myosin motor proteins, characterized by
different kinetic parameters, have been involved in this reorganization of
actin filaments. Given the limitations in studying the interactions of actin
with myosin in vivo, we propose stochastic agent-based model simulations and
develop a set of data analysis measures to assess how myosin motor proteins
mediate various actin organizations. In particular, we identify individual
motor parameters, such as motor binding rate and step size, that generate actin
networks with different levels of contractility and different patterns of
myosin motor localization. In simulations where two motor populations with
distinct kinetic parameters interact with the same actin network, we find that
motors may act in a complementary way, by tuning the actin network
organization, or in an antagonistic way, where one motor emerges as dominant.
This modeling and data analysis framework also uncovers parameter regimes where
spatial segregation between motor populations is achieved. By allowing for
changes in kinetic rates during the actin-myosin dynamic simulations, our work
suggests that certain actin-myosin organizations may require additional
regulation beyond mediation by motor proteins in order to reconfigure the
cytoskeleton network on experimentally-observed timescales.
