Kinesin and Myosin Motors Compete to Drive Rich Multi-Phase Dynamics in Programmable Cytoskeletal Composites

Abstract

The cytoskeleton of biological cells relies on a diverse population of motors, filaments, and binding proteins acting in concert to enable non-equilibrium processes ranging from mitosis to chemotaxis. The cytoskeleton’s versatile reconfigurability, programmed by interactions between its constituents, make it a foundational active matter platform. However, current active matter endeavors are limited largely to single force-generating components acting on a single substrate – far from the composite cytoskeleton in live cells. Here, we engineer actin-microtubule composites, driven by kinesin and myosin motors and tuned by crosslinkers, that restructure into diverse morphologies from interpenetrating filamentous networks to de-mixed amorphous clusters. Our Fourier analyses reveal that kinesin and myosin compete to delay kinesin-driven restructuring and suppress de-mixing and flow, while crosslinking accelerates reorganization and promotes actin-microtubule correlations. The phase space of non-equilibrium dynamics falls into three broad classes– slow reconfiguration, fast advective flow, and multi-mode ballistic dynamics – with structure-dynamics relations described by the relative contributions of elastic and dissipative responses to motor-generated forces.

Reconstituting and Characterizing Actin-Microtubule Composites with Tunable Motor-Driven Dynamics and Mechanics

“…This tunable and modular platform brings reconstitution efforts one important step closer to mimicking the cellular cytoskeleton and offers the unique ability to program its properties across a wide phase space by independently incorporating, removing, and tuning the different components. Moreover, all components of this versatile system are commercially available (see Table of Materials), except for the kinesin dimers which are purified in the Ross Lab, as described previously 50 , and available upon request. Finally, all analysis code is freely available through GitHub 49 and is based on free programming languages and software (Python and Fiji).…”

“…The following steps create actin-microtubule composites that are driven out-of-equilibrium by kinesin motors or a combination of kinesin and myosin 50 .…”

“…Data points in A and B that correspond to the three time-series analyzed in Figure7are circled in the corresponding class color (1 = purple, 2 = orange, 3 = magenta). This figure has been modified from reference50 . Please click here to view a larger version of this figure.…”

Multiscale architecture: Mechanics of composite cytoskeletal networks

“…If kinesin, myosin, and biotin-neutravidin cross-links are added simultaneously to actin-microtubule networks, different structures from interpenetrating actin-microtubule networks to amorphous clusters of different filament types evolve, depending on whether microtubules or actin filaments are cross-linked among themselves. 82 Cross-linking suppresses microscale phase separation of actin filaments and microtubules. The competition between kinesin and myosin additionally suppresses demixing of the filament types.…”