Enabling actin

Maybe there can be too much of a good thing. A new report from Woodring et al. (page 879) provides the basis for a self-limiting interaction between F-actin and c-Abl. Although the authors find that c-Abl is an important activator of actin polymerization, the resultant F-actin can shut down c-Abl, thus completing a feedback loop that limits actin polymerization.The rapid assembly and disassembly of actin fibers is required for controlling cell migration, changing cell morphology, and extending the dendrites and axons of neurons. Some extracellular signals that cause alterations in the F-actin cytoskeleton, such as integrin clustering, have also been shown to activate c-Abl, a nonreceptor tyrosine kinase with an F-actin binding site. In vitro, binding to F-actin inhibits the kinase activity of c-Abl.

Woodring et al. now demonstrate that c-Abl promotes actin...