Structure and Function of Gelsolin

Abstract

Gelsolin is a protein that exerts a variety of influences both within the cytoplasm and in extracellular fluids (reviewed in Yin 1987; Janmey et al. 1998). Intracellular gelsolin participates in regulation of cellular architecture and motility through its severing, capping and nucleating activities on actin filaments. Gelsolin itself is subject to control by calcium ions and polyphosphoinositide metabolites. While gene knockout experiments suggest that gelsolin is not essential for survival, it is necessary for rapid responses of such dynamic cells as fibroblasts, as during the process of wound healing, and platelets, as during clotting (Witke et al. 1995). Fibroblasts in which gelsolin has been overexpressed display increased motility (Cunningham et al. 1991). The secreted form of gelsolin, exemplified by that found in blood plasma, is identical in amino acid sequence to that found in the cytosol except that it incorporates a short peptide extension at the N-terminus of the cytoplasmic sequence (Kwiatkowski et al. 1986; Koepf et al. 1998). Alternative transcription initiation and selective RNA processing permit a single gelsolin gene in each species to produce distinct mRNA messages that code for both cytoplasmic and secreted forms of the protein.