MOTILE AREAS OF LEECH NEURITES ARE RICH IN MICROFILAMENTS AND 2 ACTIN-BINDING PROTEINS - GELSOLIN AND PROFILIN

Cell motility is produced by changes in the dynamics and organization of actin filaments. The aim of the experiments described here was to t est whether growing neurites contain two actin-binding proteins, gelso lin and profilin, that regulate polymerization of actin and affect non -neuronal cell motility. The distribution of gelsolin, profilin and th e microfilaments was compared by immunocytochemistry of leech neurons growing in culture. We observed that microfilaments are enriched in th e peripheral motile areas of the neurites. Both gelsolin and profilin are also concentrated in these regions. Gelsolin is abundant in filopo dia and is associated with single identifiable microfilament bundles i n lamellipodia. Profilin is not prominent in filopodia and shows a dif fuse staining pattern in lamellipodia. The colocalization of gelsolin and profilin in motile, microfilament-rich areas supports the hypothes is that they synergistically regulate the actin dynamics that underlie neurite growth.