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Motor-Driven Marginal Band Coiling Promotes Cell Shape Change During Platelet Activation
Boubou Diagouraga, Alexei Grichine, Arnold Fertin, Jin Wang, Saadi Khochbin and Karin Sadoul
Circulating quiescent platelets have a flat, discoid shape maintained by a peripheral ring of microtubules, called the marginal band. Platelets are activated after vessel injury and undergo a major shape change known as disc-to-sphere transition. It has been suggested that actomyosin contracts the marginal band to a smaller ring promoting the spherical shape. Instead microtubule motors of the dynein family slide microtubules apart leading to marginal band extension. The limited available space forces the marginal band to coil, which induces the spherical shape of the activating platelet. Actomyosin contraction will then compress the coiled marginal band and newly polymerising microtubules within the coiled ring will short-cut their original path and form the smaller microtubule ring observed in activated platelets.