UCLA

Actin cytoskeleton is important for neuronal morphology and function. Many accessory proteins, including brain-specific drebrin A and diaphanous family of formins (mDia), regulate actin dynamics in neuronal substructures, such as dendritic spines. In order to probe for possible interrelation of drebrin and mDia2 formin, we examined their combined effects on actin polymerization, bundling, and binding. We identified drebrin A as a new interacting partner of mDia2 formin. Our results suggest two sites of interaction between drebrin A and mDia2, with the C-terminal region of drebrin binding to formin’s FH2 domain and the “actin binding core” of drebrin binding to formin’s C-terminal “tails.” We found that drebrin A inhibits mDia2-driven actin nucleation without affecting the rate of its processive elongation. Drebrin also abolishes actin bundling mediated by FH2 domain of mDia2. Thus, our data contribute to the mechanistic understanding of actin regulation and its role in neuronal function and development.