Microfilaments and Cell Locomotion

Abstract

The role of microfilaments in generating cell locomotion has been investigated in glial cells migrating in vitro . Such cells are found to contain two types of microfilament systems : First, a sheath of 50-70-A in diameter filaments is present in the cytoplasm at the base of the cells, just inside the plasma membrane, and in cell processes . Second, a network of 50-A in diameter filaments is found just beneath the plasma membrane at the leading edge (undulating membrane locomotory organelle) and along the sides of the cell . The drug, cytochalasin B, causes a rapid cessation of migration and a disruption of the microfilament network . Other organelles, including the microfilament sheath and microtubules, are unaltered by the drug, and protein synthesis is not inhibited . Removal of cytochalasin results in complete recovery of migratory capabilities, even in the absence of virtually all protein synthesis . Colchicine, at levels sufficient to disrupt all microtubules, has no effect on undulating membrane activity, on net cell movement, or on microfilament integrity . The microfilament network is, therefore, indispensable for locomotion .

Role of RhoA activation in the growth and morphology of a murine prostate tumor cell line

“…Stress ®bers are contractile bundles of ®lamentous (F)-actin and myosin II that mediate cell tension development, cell adhesion, cell migration, and cell locomotion, (Chrzanowska-Wodnika and Burridge, 1996; Kreisberg et al, 1985Kreisberg et al, , 1997Bragina et al, 1976;Spooner et al, 1982). Two downstream targets of RhoA activation promote actin stress ®ber formation: (1) activation of phosphatidylinositol 5-kinase (Chong et al, 1994) whose lipid product phosphatidylinositol 3,4,5-bisphosphate activates a-actinin, an actin binding protein required for the proper assembly of actin stress ®bers (Fukami et al, 1992); and (2) activation of Rho kinase which phosphorylates myosin light chain allowing binding to F-actin and the development of the contractile bundle (Amano et al, 1997).…”

Investigation of the mechanism of retraction of the cell margin and rearward flow of nodules during mitotic cell rounding.

“…Sudden rapid retraction of the dorsal region of the mitotic cell in cytochalasin D during early or mid-rounding is difficult to interpret (Figure 3). In interphase in other types of motile cells, e.g., motile fibroblasts and glial cells, cytochalasin also causes relatively rapid retraction (Spooner et al, 1971;Croop and Holtzer, 1975). Sudden retraction is the expected phenotype of an adherent object under tension that rapidly loses adhesion.…”

Cytochalasin B: Effects on Cell Morphology, Cell Adhesion, and Mucopolysaccharide Synthesis

“…Wessels and coworkers have stated (11,12) that cytochalasin-B interferes with the spontaneous contraction of cardiac and smooth-muscle cells. These findings could not be confirmed in this study.…”

“…Since cytochalasin B blocked tail resorption in ascidian tadpoles (9,10), an activity also attributed to microfilaments, this added further support to the notion that the antibiotic interfered with a "primitive contractile" system of microfilaments present in virtually all cells. Wessels and coworkers (11)(12)(13)(14) have elaborated on this theme and presented electron microscopic observations to the effect that alterations of cortical microfilaments induced by cytochalasin B not only interfered with cell motility, but with blood clotting, cytoplasmic streaming, and embryonic morphogenesis. The site of action of cytochalasin B in the cell is not known.…”