Actin-binding proteins in the growth cone particles (GCP) from fetal rat brain: a 44 kDa actin-binding protein is enriched in the fetal GCP fraction

Abstract

Neuronal growth cones, the motile tips of growing neurites, are thought to play a significant role in nerve growth. To study the role of actin in their motility, we examined actin-binding proteins in growth cone particles (GCP) isolated from fetal rat brain, using a blot-overlay method with biotinylated actin. Among the more than ten species of actin-binding proteins in the GCP, a 44 kDa protein was found specifically in growth cones and was enriched in the cytoskeletal and the membrane skeletal subfractions from the GCP. This protein binds to actin in a Ca 2+- and Mg 2+-dependent manner, and ATP enhances its binding to actin. The protein was predominantly present in the fetal GCP, but it is expressed at a much lower level in the neonatal GCP and not detected in adult synaptosomes. The protein also bound to a deoxyribonuclease I column and was eluted by EGTA-containing buffer. The 44 kDa protein appears to be a novel actin-binding protein, since none of the known actin-binding proteins exhibit this combination of properties. Our results suggest that the protein may be involved with the early stages of neurite extension.