Cytoskeleton-Membrane Interaction and the Remodeling of the Cell Surface During Phagocytosis and Chemotaxis

Abstract

Chemotaxis and phagocytosis are membrane processes. They begin with the interaction of particles or chemoattractants with cell surface receptors. Their earliest manifestations include changes in ion fluxes (1), the activation of membrane oxidases (2) and the physical reorganization of the membrane and underlying cytoskeleton to form new structures: pseudopods during phagocytosis, uropods and lamellipodia during chemotaxis (3). In this paper we review evidence for a remarkable topographical reorganization of membrane structural determinants and of surface functions during chemotaxis and phagocytosis. It will be shown that membrane receptors may segregate to specific regions of the surface. After ligand binding to these receptors, the resulting complexes may be translocated to other specific regions. Functions such as endocytosis and membrane transport are also restricted to specified areas of the surface. The mechanisms that initiate and sustain these topographical asymmetries will be explored. Recognition of these membrane events may clarify several characteristic properties of polymorphonuclear leukocytes (PMN) and macrophages, for example their ability to maintain unidirectional movements in very shallow chemotactic gradients or to preserve the integrity of membrane transport systems during the removal of cell surface by phagocytosis.