Effect of Colchicine, Colcemid, and Vinblastine on the Agglutination, by Concanavalin A, of Transformed Cells

409

152

An analysis of the inhibition by concanavalin A of the mobility of lymphocyte surface receptors is used to construct an hypothesis on membrane receptor-cytoplasmic interactions. It is proposed that binding of multivalent lectins alters the interaction of an assembly of colchicine-binding proteins with lectin receptors and other receptors, and reciprocally that the state of the colchicine-binding assembly alters the mobility and distribution of surface receptors on the cell membrane. Observations of the effect of colchicine and related drugs on the inhibition of receptor mobility by concanavalin A lend support to this hypothesis. The proposed model has several implications for studies of the initial events of mitogenesis in lymphocytes as well as for cellcell interactions in general.

Section: A Model For Receptor-cytoplasmic Interactionssupporting

confidence: 53%

Receptor Mobility and Receptor-Cytoplasmic Interactions in Lymphocytes

Edelman

Yahara

Wang

1973

409

152

“…CBP appear to be essential for the selective removal of lectin receptors from the plasma membrane. This seems difficult to reconcile with the concept that CBP anchor surface elements geographically, a possibility originally suggested by us (6)(7)(8) and recently elaborated by Edelman (25). This paradox is resolved if we postulate that CBP, rather than anchoring surface elements, are required for their directed movement.…”

Section: Discussionmentioning

confidence: 89%

Effects of Phagocytosis and Colchicine on the Distribution of Lectin-Binding Sites on Cell Surfaces

Oliver

Ukena

Berlin

1974

143

The effect of phagocytosis on lectin binding to plasma membranes of polymorphonuclear leukocytes was examined. The specific activities of binding sites of concanavalin A and Ricinus communis agglutinin (defined as M&g of lectin bound per 100 Mg of membrane protein) were measured on isolated membranes; they decreased in parallel with phagocytosis. Our data suggest that this removal occurs by concentration of binding sites into internalized membrane. Colchicine and vinblastine, which did not inhibit phagocytosis, prevented the selective removal of lectin-binding sites from the surface. It was also shown that at 370 lectins induce their own internalization. This property was used to define operationally three classes of lectin receptors, one of which is most extensively removed from plasma membrane during phagocytosis. Based on other morphological studies in which it is shown that before phagocytosis the surface distribution of concanavalin-binding sites is random, it is inferred that phagocytosis alters surface topography by inducing the selective movement of binding sites into membrane undergoing internalization and that colchicine-sensitive proteins are essential for this imposed topographical reorganization.According to the fluid mosaic model of cell surfaces, proteins are free to diffuse in the membrane of cells and thus should assume a random or homogeneous distribution (1). Yet, several studies have indicated that certain components (2) and functions (3) dependent on proteins are disposed over the surface nonrandomly. The resolution of this paradox is suggested by some morphological studies of the distribution of concanavalin A (Con A)-binding sites (CABS) on transformed cells (4, 5); the inherent distribution of CABS is random but CABS may be induced to cluster (i.e., assume a nonrandom distribution) by addition of exogenous Con A. We have also presented evidence that colchicine-sensitive proteins may modify the movement of CABS (6, 7) and membrane-transport proteins (8).During phagocytosis, particles are enveloped by cytoplasmic membrane which is then withdrawn into membranebound intracellular vesicles. Suitable particles can stimulate the internalization of a large portion of the membrane (3). Thus, phagocytosis causes the removal of an operationally defined region of the cell surface, permitting examination of the properties and composition of the residual surface mem-

“…It thus seems probable that the effects of colchicine are a result of its inhibition of tcrotubule Moreover, the effects of preincubation with colchicine do not persist after the cells are broken, nor does colchicine affect directly either basal or hormone-stimulated adenylate cyclase activity in leukocyte membrane preparations (data not shown), even though these preparations respond readily to the hormones themselves, suggesting that the colchicine effect on cyclic AMP levels is a result of its interaction with cytoplasmic, rather than membrane-associated, tubulin. It has been suggested that colchicine-sensitive cytoplasmic structures (presumably microtubules) may interact with the cell membrane in such a way as to place constraints on the mobility of certain receptors (22)(23)(24)(25). Previous work has involved primarily lectin-binding receptors.…”

Section: Discussionmentioning

confidence: 99%

Effects of colchicine on cyclic AMP levels in human leukocytes

Rudolph

Greengard

Malawista

1977

121

The increase in human leukocyte adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels seen in response to various substances was markedly potentiated by colchicine and other agents that affect microtubule assembly. Addition of dI-isoproterenol (2 AiM) or prostaglandin El (10 ttM), together with the phosphodiesterase inhibitor isobutylmethylxanthine (1 mM), caused a much greater increase in cyclic AMP in colchicine-pretreated cells tan in control cells. With isoproterenol (2 MM) plus isobutylmethylxanthine (1 mM), cyclic AMP levels rose about 3fold but, in combination with colchicine, these drugs caused a more than 15-fold increase in cyclic AMP. The effects of colchicine were both time-and dose-dependent; they could be seen'within 1 min after addition of colchichme or at concentrations as low as 10 nM. In addition to its potentiation of hormonally induced increases in cyclic AMP levels, colchicine also potentiated the effect of isobutylmethylxanthine alone on leukocyte cyclic AMP levels. Vinblastine, vincristine, podophyllotoxin, and oncodazole all had effects similar to those of colchicine but blmicolchicine did not. The data suggest that cytoplasmic nticrbtubules interact with the leukocyte plasma membrane to impose constraints on the expression of hormone-sensitive adenylate cyclase; the therapeutic effects of colchicine may depend in part upon the relaxation of such constraints. Moreover, the synergism described here between colchicine-like agents and hormones is of potential therapeutic importanceiln clinical conditions in which either alkaloid or hormone has been useful separately. IThe cyclic nucleotide levels of human leukocytes (both granulocytes and mononuclear cells) are controlled by a number of hormones and pharmacological agents (1-5). f3-Adrenergic agonists (isoproterenol, epinephrine), histamine, and prostaglandin E1 (PGE1) all raise adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels in these cells; the muscarinic cholinergic agonists (acetylcholine, carbamylcholine) raise cyclic GMP levels. In granulocytes, a functional significance of cyclic nucleotides has been suggested by experiments showing that increases in cyclic AMP inhibit the degranulation of lysosomes that normally accompanies phagocytosis, whereas increases in cyclic GMP enhance degranulation (2, 3, 5, 6). Colchicine and vinblastine, agents that cause the disappearance of cytoplasmic microtubules by preventing their assembly (7-10), also inhibit degranulation (6, 11-13); it is through this inhibition of microtubule assembly, with consequent effects on microtubuleassociated functions, that colchicine is thought to exert its therapeutic anti-inflammatory action in acute gouty arthritis and other disorders (14). We now report that colchicine and other agents that interfere with microtubule assembly increase cyclic AMP levels in human leukocytes and potentiate the effects of hormones on cyclic AMP levels in these cells. METHODSLeukocytes were obtained from freshly drawn, heparinized blood from healthy, adult donors by de...