Vendredi 20 décembre 2024 à 11h00, salle 357, IUSTI
Abstract: Biological systems can self-organize at large scales by coordinating small constituents that each consume energy from the environment. Our group has recently shown that myosin-II or V motors and a parallel network of polymerizing actin filaments can self-organize in vitro into polar bundles that exhibit wave-like beating (Pochitaloff et al., Nature Physics 18, 1240 (2022)), resembling beating of eukaryo4c flagella. Here we study in vitro the emergence of wave-like bea4ng driven by myosin-X motors, which are involved in vivo in filopodia assembly and cargo transport along parallel actin networks. Despite their contrasted biophysical properties, we found that myosin V and X produce wave- like beating with similar waveforms (Fig. 1). The myosin-X fluorescence signal was highest at the curved and dynamic tips of the bundles. This was not because there were more myosins there: the total myosin quantity in the bundle actually decreases towards the bundle apex; yet, the myosin signal was stronger there, because the amount of myosin per filament was higher. Remarkably, actin-bending waves were associated with waves of the bundle width that propagated toward the bundle’s tip at the same speed, resulting in a strong periodic modulation of actin-filament density. This behavior contrasts with that previously evinced by beating bundles driven with myosin V, which instead show sudden motor recruitment at a threshold curvature of the bundle followed by propagation toward the bundle’s tip with little change in motor quantity and bundle width. Finally, we observed prominent streaming of myosin-X motors in the loose and static por4on of the actin bundle; streaming was not seen with myosin V. Altogether, these experiments ought to shed light on the feedback control between motor activity and bending of filament bundle depending on the biophysical properties of the motors.