Biophysics of the leading lamella.

Abstract

Several chapters in the proceedings have amply demonstrated that the biochemistry and structural biology of the leading lamella are complicated [Soll, 1988; Hartwig and Yin, 1988; Condeelis, et al., 19881. Therefore, I will approach the phenomenon of cell locomotion by posing two questions about the physics of this organelle: What are the mechanical forces that drive cell protrusion? How are the chemical and physical events coordinated? Too little is known to answer these questions definitively; but, enough is known to enable us to nominate some candidates. However complex the biochemistry of cell protrusion is, the cell must obey the laws of mechanics, which narrows the possibilities for protrusive forces much more than it constrains the chemical reactions that generate them. We now know that the plasma membrane-far from a simple oily film coating the cytoskeleton-is both a catalytic surface and a pool of reactants. The theme of my talk will be that the “control system” that directs cell protrusion resides in the cytoplasmic face of the membrane surrounding the leading lamella. Because this is not a “real” paper, but rather a rough transliteration of a talk, the format of my presentation will be bite-sized panels, each addressing a single issue. The diagrams in these panels are intended to be heuristic, not representational. Because my aim is to sion, adhesion, and retraction. Inherent in the properties of the leading lamella are many characteristics of cell locomotion; these include contact inhibition taxes: chemotaxis, haptotaxis, galvanotaxis substrate guidance 8 ruffles retraction induced spreading tension inhibition of spreading centripetal particle movement surging and steady spreading