Polarization of endocytosis and receptor topography on cultured macrophages.

Abstract

In the J774 .2 macrophage cell line, microtubule disassembly by colchicine causes the polarization of membrane functions and structure. Colchicine-treated cells develop a bulge or protuberance that is bordered by microvillous membrane . The protuberance is the site of concanavalin A cap formation. The fluid pinocytosis of horseradish peroxidase and of fluorescein-and rhodamine-conjugated high molecular-weight dextrans, the adsorptive pinocytosis of concanavalin A, and the concentration and phagocytosis at 37°C of a range of phagocytic particles (IgG-and complement-opsonized erythrocytes, complement-opsonized zymosan, latex spheres, albumin-stabilized oil droplets) are all similarly restricted to the protuberance . A reduction in the rate of dextran pinocytosis, determined by fluorimetry, and reductions in phagocytic rates for oil emulsion and IgG-opsonized erythrocytes accompany the polarization of endocytic activity in colchicine-treated J774 .2 macrophages.Membrane receptors for phagocytic particles are not confined to the protuberance but rather may display their own unique topographical asymmetry. The inherent topography of receptors was inferred from particle distribution under conditions that limit particle-receptor redistribution (after labeling at 4°C or a very brief incubation at 37°C) . Under these restrictive conditions, latex binding sites were detected over the whole membrane whereas receptors for IgGopsonized erythrocytes, aggregated IgG, complement-opsonized erythrocytes, and complement-opsonized zymosan were excluded from the protuberance . Thus, functional (endocytosis) and structural (inherent receptor distribution) analyses of membrane topography define different patterns of asymmetry in protuberant cells .The asymmetry induced in J774 .2 macrophages by colchicine is highly analogous to the functional and structural polarity of epithelial cells . Exploration of this analogy may provide insight into the development of polarized epithelia and, more generally, into mechanisms by which specialized areas of membrane are established .In a variety of leukocytes and macrophages, microtubule disassembly by colchicine leads to development of a ruffled protuberance underlain by microfilaments at one pole of the cell . We and others have shown that the protuberance provides a focus for the movement at 37°C of concanavalin A (Con A)-receptor complexes from their inherently dispersed distribution into a surface cap (1) . In the course of this earlier work, we also noted the similar shapes and ultrastructure of colchicinetreated leukocytes and polarized epithelial cells . In particular, the microfilamentous meshwork that underlies the protuberance of microtubule-depleted leukocytes is reminiscent of the terminal web and brush border of intestinal epithelium (23). It is well known that many surface functions and enzymatic activities are polarized to the microvillous border of epithelial TFiE JOURNAL Of CELL BIOLOGY " VOLUME 86 JULY 1980 199-211 © The Rockefeller University Press -0021-9525/80/07/0199...

Membrane protein redistribution during differentiation of cultured human erythroleukemic cells.

“…It is interesting that none of the organelles is found in the budding protrusion, an observation that has been made in cells that produce similar structures after colchicine treatment (31). This may result from the existence of a highly organized array of cytoskeletal compo- nents, especially microfilaments, in the protrusion that physically excludes the organelles.…”

Phosphorylation of myosin light chain during capping of mouse T-lymphoma cells.

“…Recently, Walter et al . (42) have shown that colchicine is able to induce macrophages to accumulate phagocytic and pinocytic vesicles as well as Con A receptors into a cap structure at one pole of the cell . The primary mode of action of colchicine has been commonly considered to involve the disassembly of microtubules (4,5,22,27,44).…”

A Novel Cellular Protein, VPEF, Facilitates Vaccinia Virus Penetration into HeLa Cells through Fluid Phase Endocytosis

“…To test this, we incubated HeLa cells with either fluorescence-labeled transferrin or dextran. Transferrin undergoes clathrin-mediated endocytosis, whereas dextran is taken up by fluid phase endocytosis (7,64). Each of these fluorescent ligands was added to HeLa cells, which were then fixed, permeabilized, and stained with anti-M2 Abs.…”