TOWARD A NEW CONCEPT OF CELL MOTILITY - CYTOSKELETAL DYNAMICS IN AMEBOID MOVEMENT AND CELL-DIVISION

This chapter reviews historical and current studies relevant to cytoskeletal dynamics, with emphasis on Dictyostelium cytoskeletons. Cytoskeletal dynamics is the cytoskeletal reorganization that occurs as a consequence of monomer–polymer transition and protein–protein as well as protein–membrane interactions. Actin constitutes as much as 10% of the total protein in nonmuscle cells. The dynamism of cytoplasm exhibits as a thixotropic transition with polymerization and crosslinking of the filaments through regulation of pH, calcium, and associating proteins. The cortical-gel contraction hypothesis predicted that actomyosin ATPase produces the energy of contraction in nonmuscle systems. The dynamics of nonmuscle-cell motility also manifests as projection rather than contraction. Many signal-transduction events relate significantly to cytoskeletal dynamics, such as chemotactic and growth stimulation that cause transient changes in cell shape, cell motility, and cell division. The actin cytoskeleton is probably regulated by the factors involved in the signal-transduction cascade. Profilin which is a low-molecular weight G-actin-binding protein, might play a significant role in regulating actin polymerization in the cytoplasm by binding to G-actin. © 1993, Elsevier Science Publishers, B.V.