MECHANISMS OF HUMAN BASOPHIL & MAST CELL DESENSITIZATION

嗜碱性粒细胞和肥大细胞介质释放是其核心特征 急性和慢性过敏反应。 然而， 已知人体信号传导的生化性质 这种细胞。 这项建议的重点是研究， 阐明一些重要的生物化学事件，在这两个IgE 介导和单价激素诱导分泌。 主 这些研究的目的是阐明 尽管也将作出重大努力， 对理解激活事件有帮助。 特别是，作用 磷脂代谢和蛋白激酶C的活化， 将检查脱敏。 我们最近证明了 IgE介导的组胺在嗜碱性粒细胞和肺中的释放 肥大细胞伴随着磷脂酰肌醇的变化， 膜相关蛋白激酶C活性增加， 胞质钙离子升高。 看来蛋白激酶C 活性增加（与IgE介导的刺激），即使在 缺乏外部钙，这表明这种酶也可能 在人嗜碱性粒细胞的脱敏过程中发挥作用， 肥大细胞 因此，我们假设蛋白激酶C 磷酸化5 '-磷酸单酯酶， 在将三磷酸肌醇代谢为其非活性形式中有活性。 由于目前假设三磷酸肌醇介导 细胞溶质钙的升高， 解释脱敏现象。 证实 这种脱敏测量模型将由 磷脂周转，特别是磷脂酰肌醇，以及 磷脂酶C活化的两个副产物，肌醇 三磷酸盐和二酰基甘油，试图描绘更多 准确地说，它们在激活中的作用。 研究还将涉及 测量蛋白激酶C的激活，并确定 蛋白质通过其活化而磷酸化，特别是在 无钙缓冲液条件。 磷酸化5 '- 将直接检查磷酸单酯酶及其活性 在脱敏嗜碱性粒细胞和肥大细胞中。

Basophil and mast cell mediator release is a central feature of both acute and chronic allergic reactions. However, little is known of the biochemical nature of signal transduction in human cells of this type. This proposal focuses on studies which will elucidate some of the important biochemical events in both IgE mediated and univalent hormone induced secretion. The primary goal of these studies is to elucidate the mechanism of desensitization although significant effort will also be applied towards understanding activation events. In particular, the role of phospholipid metabolism and protein kinase C in activation and desensitization will be examined. we have recently demonstrated that IgE-mediated histamine release in both basophils and lung mast cells is accompanied by changes in phosphotidyinositol, increased activity of membrane associated protein kinase C and elevations in cytosolic calcium. It appears that protein kinase C activity increases (with IgE-mediated stimulation) even in the absence of external calcium suggesting that this enzyme may also play a role in the desensitization process of human basophils and mast cells. As such, we hypothesize that protein kinase C phosphorylates a 5'-phosphomonoesterase which in turn becomes active in metabolizing inositol trisphosphate to its inactive form. Since inositol trisphosphate is currently hypothesized to mediate elevations in cytosolic calcium this proposed scheme could account for the phenomenon of desensitization. To substantiate this model of desensitization measurements will be made of phospholipid turnover, in particular phosphotidyinositol, and the two side products of phospholipase C activation, inositol trisphosphate and diacylglercerol in an effort to delineate more accurately their role in activation. Studies will also involve measurements of protein kinase C activation and determine which proteins are phosphorylated by its activation, particularly under calcium-free buffer conditions. Phosphorylation of 5'- phosphomonoesterase will be directly examined as will its activity in desensitized basophils and mast cells.