MEMBRANE-ACTIVITY AND TOPOGRAPHY OF F-MET-LEU-PHE TREATED POLYMORPHONUCLEAR LEUKOCYTES - ACUTE AND SUSTAINED RESPONSES TO CHEMOTACTIC PEPTIDE

Abstract

The chemotactic peptide f-Met-Leu-Phe causes a dramatic stimulation of membrane ruffling and of fluid pinocytosis in [rabbit] polymorphonuclear leukocytes (PMN). These responses are maximal by 1 min. and subside within 5-10 min. The same immediate response characterize cells exposed to several peptide hormones and may thus represent an essential component of target cell activation by peptides. The stimulation of the whole membrane following f-Met-Leu-Phe binding is succeeded by the development of a polarized cell shape with a posterior uropod and a broad anterior lamellipodium, both subtended by microfilaments.Membrane components and functions segregate into distinct domains on polarized PMN. Succinyl concanavalin A receptor complexes are capped and internalized by receptor-mediated endocytosis at the uropod; the uptake by fluid pinocytosis of fluorescein-dextran is restricted to the uropod, and coated pits and coated vesicles are concentrated at the uropod. The lamellipodium excludes coated pits and lacks pinocytic activity but shows preferential binding of ig aggregates, presumably to Fc receptors. The origin and physiologic implications of these asymmetries of membrane molecular and functional topography on polarized cells are discussed.