Key result
Capping protein and formins can simultaneously bind to actin filament barbed ends to form a ternary complex, leading to mutually weakened binding and rapid displacement of one by the other.
Formin and capping protein can simultaneously bind to actin filament barbed ends, allowing for rapid displacement and functional coregulation of filament assembly.
May modulate actin networks in cells; leaves open relevance to cardiac cytoskeletal function.
Proteins targeting actin filament barbed ends play a pivotal role in motile processes. While formins enhance filament assembly, capping protein (CP) blocks polymerization. On their own, they both bind barbed ends with high affinity and very slow dissociation. Their barbed-end binding is thought to be mutually exclusive. CP has recently been shown to be present in filopodia and controls their morphology and dynamics. Here we explore how CP and formins may functionally coregulate filament barbed-end assembly. We show, using kinetic analysis of individual filaments by microfluidics-assisted fluorescence microscopy, that CP and mDia1 formin are able to simultaneously bind barbed ends. This is further confirmed using single-molecule imaging. Their mutually weakened binding enables rapid displacement of one by the other. We show that formin FMNL2 behaves similarly, thus suggesting that this is a general property of formins. Implications in filopodia regulation and barbed-end structural regulation are discussed.
No takes yet. Share an insight, caveat, or question.
Shekhar et al. (2015) studied Actin filament assembly (in vitro). Formin (mDia1, FMNL2) and Capping Protein (CP) was evaluated on Formation and kinetics of the ternary complex at actin filament barbed ends. Capping protein and formins can simultaneously bind to actin filament barbed ends to form a ternary complex, leading to mutually weakened binding and rapid displacement of one by the other.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: