Extracellular matrix-cytoskeleton interactions in locomoting embryonic cells

Abstract

Despite the great advances in understanding the composition and organization of the cytoskeleton in recent years, the molecular mechanism of cell locomotion is poorly understood. One of the main reasons for our ignorance is that the biochemical machinery responsible for these movements is not localized precisely to a single structure, but is widely distributed throughout the cell. Furthermore, because the machinery is labile and easily disrupted during biochemical fractionation, it is difficult to isolate in a functional form. So far, most studies on cell locomotion used fibroblasts as a model system. This system appeared particularly suitable for understanding not only the organization of cytoskeletal elements within the cells but, most interestingly, the flow of membrane components throughout the cell surface during extension of the leading lamellipodia and retraction of the trailing edge (for reviews, ABERCROMBIE 1980, BRETCHER 1984, ISHIHARA et al. 1988, RINNERTHALER et al. 1988). However, many of these studies dealt with surface molecules that are not involved in the adhesion of the cell to its substratum and thus that probably exhibit a different behavior within the plane of the membrane. A possible alternative is to examine in molecular terms how the moving cells interact with their substratum. Since cells naturally crawl in a complex network of extracellular matrix molecules, it is necessary to search among these molecules the ones which mediate the anchorage of the