Fig. 2. Proposed dependence of cell shape on the endocytic properties of the attaching integrin. The circulating integrin is shown in brown and the cell is attached to the substratum only where the integrin has a sufficient concentration on the ventral aspect. (A) A quickly circulating integrin. (B) A more slowly circulating integrin. (C) An integrin that is neither concentrated nor depleted during endocytosis. The cell becomes less snail-shaped as the rate of circulation of the integrin decreases until the cell is quite spread out and flat.