Concanavalin A stimulates phospholipid methylation and phosphatidylserine decarboxylation in rat mast cells.

Abstract

When histamine release from rat peritoneal mast cells is stimulated by concanavalin A, membrane phospholipids are methylated in the early stage of this process. Exogenously added phosphatidylserine enhances the concanavalin A-induced histamine release, and at the same time the lectin markedly stimulates the decarboxylation and methylation of phosphatidylseriine. Within minutes after the addition of concanavalin A to rat mast cells, the newly methylated phosphor lipids begin to disappear and an increased formation of lysophosphatidylcholine is observed. When rat mast cells are treated with concanavalin A in the absence of Ca2+, phospholipid methylation is stimulated but no significant release of histamine is detected. The subsequent exposure of the pretreated cells to Ca2+ causes increased release of histamine and degradation of methylated phospholipids. The inhibition of either synthesis or degradation of methylated phospholipids results in the inhibition of histamine release. These observations suggest that the synthesis and degradation of methylated lipids are an intrinsic part of the biochemical mechanism that modulates histamine release from mast cells.Lectins such as concanavalin A (Con A) and the antibody anti-IgE stimulate mast cells to release the biogenic amine histamine (1, 2). Con A is a model compound for anti-IgE because the processes of histamine release by these agents have many similarities (2, 3). Con A or anti-IgE binding causes receptors to cluster on cell membranes (4). In turn, this triggers a series of intracellular events which lead to the secretion of biogenic amines by exocytosis (1). Phosphatidylserihe markedly enhances the release of histamine from rat mast cells by Con A (5). Previous work in our laboratory has shown that phospholipid methylation influences many membrane events such as membrane fluidity (6), lipid translocation (7), and coupling of the f3-adrenergic receptor to adenylate cyclase (8).In view of the dynamic role of phospholipids in membrane function, we examined the effect of Con A on lipid methylation, phosphatidylserine metabolism, and histamine release in rat mast cells. Here, we report that Con A stimulates phospholipid methylation, which is followed by the disappearance of methylated lipids with the simultaneous release of histamine. It was also observed that, after the treatment of rat mast cells with Con A, phosphatidylserine is decarboxylated and methylated. METHODS AND MATERIALSMast Cell Preparation. Mast cells were isolated from rat peritoneal fluid with Hanks' buffer containing 0.1% bovine serum albumin and heparin at 10 units/ml and were purified by centrifugation with a gradient of human serum albumin (9). Mast cells (>92% pure as determined by staining with methylene blue) were suspended in flanks' buffer containing 0.1 mM The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.L-[methyl-3H]methi...

Direct demonstration of increased intracellular concentration of free calcium as measured by quin-2 in stimulated rat peritoneal mast cell.

“…Aliquots of passively sensitized and quin-2-loaded mast cells were suspended in Hepes buffer containing 1.6 mM Ca2' and 1.0 mM Mg2' and were pretreated with 3-deazaadenosine (500 ,uM) and L-homocysteine thiolactone (100 ,uM) for 1 hr or with 2 mM theophylline for S min. EGTA and PtdSer at final concentrations of 3 mM and sample A, 20.6% ± 0.3%; sample B, 11.3% ± 1.2%; sample C, 6.5% ± 0.9%; sample D, 2.3% ± 1.5%. 50 ,g/ml, respectively, were added to an aliquot of each cell suspension.…”

Evidence against a requirement for phospholipid methylation in adenylate cyclase activation by hormones

“…Phospholipid methylation has been implicated in the transduction through plasma membranes of a variety of receptor-mediated signals [ 1 ], including activation of adenylate cyclase by isoprenaline [2,3], lectin-induced formation of arachidonic acid, Ca 2÷-influx and mitogenesis [4,5], antigen-stimulated histamine release [4,6], and response to chemoattractrants [1,7]. Transmethylation is one of the 2 pathways for the formation of phosphatidylcholine, proceeding by successive steps of enzymatic transfer of methyl-groups to phosphatidylethanolarnine from the donor S-adenosylmethionine (AdoMet), to yield the final product via mono-and di-methylated intermediates [8][9][10][11].…”

“…Transmethylation is one of the 2 pathways for the formation of phosphatidylcholine, proceeding by successive steps of enzymatic transfer of methyl-groups to phosphatidylethanolarnine from the donor S-adenosylmethionine (AdoMet), to yield the final product via mono-and di-methylated intermediates [8][9][10][11]. The evidence for the hypothesis that this transmethylation is involved in linking receptor signals to cellular responses is derived from experiments showing that phospholipid methylation led to increased membrane fluidity [12], that the various kinds of cell activation were associated with methylation of phosphatidylethanolamine [1][2][3][4][5][6], and that some of these processes could be blocked by the use of methyltransferase inhibitors [4][5][6]13]. Still the Abbreviations: AdoMet, S-adenosyl-L-methionine; Hey, homocysteine; AdoHcy, S-adenosyl-L-homocysteine; c3Ado, 3-deazaadenosine; c3AdoHcy, S-3-deazaadenosyl-L-homoeysteine; PuoHcy, a purine nucleoside analogue of AdoHcy; MIX, l-methyl-3-isobutylxanthine; Hepes, 4(2-hydroxyethyl)-1-piperazineethanesulfonic acid * To whom correspondence should be addressed causal relationship between these phenomena may be questioned [ 14,15].…”

Selective inhibition by vasocortin of histamine release induced by dextran and concanavalin‐A from rat peritoneal cells

“…Furthermore Con A stimulates phospholipid methylation and phosphatidylserine decarboxylation in rat mast cells suggesting that the synthesis and degradation of methylated lipids are an intrinsic part of the biochemical mechanism that modulates histamine release from these cells (Hirata et al, 1979).…”