Fig. 3. Levels of podocalyxin expression might explain its apparently contradictory roles in cell adhesion. (A) Membrane-protein-segregation model. Low levels of podocalyxin establish apical domains and force integrins to the basal surface of cells, thereby enhancing cell adhesion. (B) High levels of podocalyxin strongly induce microvillus formation. Dramatic relocalization of actin to the apical membrane to support formation of microvilli might deplete basolateral actin, thereby disrupting integrin-mediated adhesion.