Identification of Different Binding Partners of the F‐BAR Proteins Cdc42 Interacting Protein 4 (CIP4) and Formin Binding Protein 17 (FBP17) in Cortical Neurons

Abstract

During neuronal development, neurons perform many dynamic processes, including migration and differentiation, which require the coordination of movements between both the plasma membrane and the underlying cytoskeleton. The Cdc42 Interacting Protein 4 (CIP4) subfamily of F‐BAR proteins contains an N‐terminal F‐BAR domain that can interact with the plasma membrane and C‐terminal HR1 and SH3 domains that can interact with Rho GTPases and actin associated proteins, respectively. F‐BAR proteins, which function in detecting and inducing membrane curvature, can effectively link the plasma membrane and the cytoskeleton. Previous studies have shown that CIP4 and another family member, Formin Binding Protein 17 (FBP17), exhibit distinct functions in neurons. CIP4 tends to accumulate in the extending peripheral membrane, inhibiting neurite protrusion, while FBP17 tends to localize in membrane tubules, function in endocytosis, and assist in neurite/axon outgrowth. In this work, we used Western blot and immunoprecipitation assays to show that CIP4 and FBP17 interact with different subsets of proteins to produce their distinctive functions. We have shown previously that CIP4 colocalizes with actin‐associated proteins such as WASP Family Verprolin‐Homologous Protein 1 (WAVE1) and Disheveled Associated Activator of Morphogenesis 1 (DAAM 1). Here we will determine if WAVE1 and DAAM1 form a complex with CIP4 and if FBP17 interacts with a different set of proteins than CIP4 in cortical neurons, including N‐WASP (Neural Wiskott‐Aldrich syndrome protein) and dynamin. Results from these studies will help determine how two very similar proteins function in entirely different processes in developing neurons.