Coordinated regulation of Capping Protein by CARMIL and V-1/myotrophin

Capping Protein (CP) plays a central role in controlling actin filament dynamics in almost all eukaryotic cell types by virtue of its ability to block monomer addition and loss at the barbed end of the actin filament. Like other proteins that control actin assembly, CP is subject to regulation. Here we focus on two direct regulators of CP-CARMIL and V-1/Myotrophin. Specifically, we review recent biochemical, structural, imaging, and cell biological data that argue these two proteins cooperate to create a regulatory cycle for CP that controls its availability, activity, and site of action in the cell. Finally, we discuss unresolved aspects of this regulatory cycle and highlight how it may provide the cell with new avenues for adjusting its "actin phenotype".