Normal filopodia extension in VASP-deficient platelets upon activation by adhesive matrices or soluble agonists.

摘要

Shape change is one of the earliest visible responses after platelet activation with a soluble agonist or following contact with an adhesive substratum (1). Platelet shape change is a composite of several distinct morphological changes. Early observations reported that ADP-activated platelets undergo transformation from a smooth discoid shape, to discs extending a few short pseudopodia, and progressively to spheres with numerous long filopodial extensions (1). The same types of transformations have since been observed also in response to adhesive matrices such as von Willebrand factor (VWF) (2) and fibrinogen (3). On these matrices progressive growth of lamellipodia finally results in extensive platelet spreading. Whereas filopodia and lamellipodia are membrane protrusions driven by actin polymerisation, sphering of the platelet body has been linked to a distinct process powered by an actomyosin-driven contraction, tubulin depoly-merisation, and cortical actin cytoskeleton severing.