Cytoskeletal regulation of concanavalin A capping in pulmonary alveolar macrophages

Abstract

CONCANAVALIN A (con A) capping occurs in polymorphonuclear leukocytes (PMN) and is thought to be dependent on disruption of microtubules with subsequent lateral movement of lectin receptors to a polar region in the plasma membrane¹. Capping in PMN is induced by colchicine but is blocked by cytochalasin B, an inhibitor of microfilament assembly². Based on these observations, a cytoskeletal system that effects transmembrane control of receptor mobility has been proposed. The microtubules system interacts directly or indirectly with membrane components to limit the mobility of surface receptors while the contractile system of microfilaments may enhance the movement of these receptors into caps³. Here we report that capping also occurs in guinea pig alveolar macrophages (AM), and that the factors which regulate AM surface receptor movement differ dramatically from those in PMN. AM are capped by cytochalasin B alone, which is contrary to the experience with the PMN. AM capping is dependent on oxidative phosphorylation and the cap is associated with formation of a striking uropod (Fig. 1).