SIGNAL TRANSDUCTION BY THE HIGH AFFINITY IGE RECPTOR

IgE的高亲和力受体FcEpsilonRl的交联（发现 肥大细胞和嗜碱性粒细胞），是导致 IgE依赖性脱粒和炎症介质的释放。 这 是速发型超敏反应的触发因素， 许多特应性疾病如过敏性 鼻炎和过敏性哮喘。 磷酸肌醇（Pls）的水解， 由磷酸酶C（PLC）催化，与激活 这种受体被认为对Fc ε RI有很大贡献， 刺激脱颗粒。 使用大鼠嗜碱性白血病（RBL）细胞， 肥大细胞类似物，我们已经开发了一种新的，无细胞的， 细胞质耗尽的系统，其中研究的机制， FcEpsilonRI激活PLC。 与传统的膜制备方法不同， 这意味着，这些“RBL细胞幽灵”在 IgE受体交联和PI水解。 没想到的是， FcEpsilonRI介导的PI水解被5 mM磷酸烯醇式丙酮酸（PEP），这种效应持续存在于鬼， 已经被细菌毒素渗透， 分子。RBL细胞重影系统将用于实现 以下目的：1）表征RBL细胞幻影系统， 透化，并确定PEP在 FcEpsilonRI介导的PI水解的激活不依赖于其自身的功能。 再生ATP的能力; 2）检查ATP磷酸化的作用 水分子、磷脂和蛋白质 FcEpsilonR 1介导的触发; 3）扩大我们的初步证据， 一种新的磷酸化的含水产物，峰“y”，在 FcepsilonR 1介导的触发，以及4）检查可用的变体RBL 细胞系中特异性缺陷的细胞， PLC的ATP依赖性激活和/或PEP依赖性增强 依赖ATP的信号。 这些研究将确定ATP和PEP在IgE中的作用。 受体介导的PLC激活，增加我们对 这种信号被传递的机制。 在于所述 负责这种作用的分子可以是Fc ε RI特异性的， 这一信息有可能导致新的药物制剂 用于预防速发型超敏反应。 上 另一方面，如果PEP的作用最终被发现是形成 一种新的信号转导模式， 聚集的信号启动，这些发现可能有 对我们理解T细胞和B细胞上的抗原受体有很大影响 细胞以及巨噬细胞上的Fc γ受体。

Cross-linkage of the high affinity receptor for IgE, FcEpsilonRl (found on mast cells and basophils), is the initial event leading to IgE-dependent degranulation and release of inflammatory mediators. This is the trigger for immediate hypersensitivity reactions and thus is the primary event underlying a number of atopic diseases such as allergic rhinitis and allergic asthma. Hydrolysis of phosphoinositides (Pls), catalyzed by phosphohpase C (PLC), is closely linked to activation of this receptor and is thought to contribute substantially to FcepsilonRI- stimulated degranulation. Using rat basophilic leukemia (RBL) cells, a mast cell analog, we have developed a novel, cell-free, cytoplasm-depleted system in which to study the mechanism whereby FcEpsilonRI activates PLC. Unlike membranes prepared by classical means, these "RBL cell ghosts" retain a functional relationship between IgE receptor cross-linkage and PI hydrolysis. Unexpectedly, FcEpsilonRImediated PI hydrolysis is greatly stimulated (4-15 fold) by 5 mM phosphoenolpyruvate (PEP) and this effect persists in ghosts that have been permeabilized by bacterial toxins to allow diffusion of small molecules. The RBL cell ghost system will be used to achieve the following aims: 1) characterize the RBL cell ghost system following permeabilization and determine if the role of PEP in FcEpsilonRI-mediated activation of PI hydrolysis is independent of its ability to regenerate ATP; 2) examine the role ATP to phosphorylate aqueous molecules, phospholipids, and proteins during FcEpsilonR1-mediated triggering; 3)enlarge our preliminary evidence that a novel phosphorylated aqueous product, peak "y", is generated during FcepsilonR1 -mediated triggering, and 4) examine available variant RBL cell lines for ones which are specifically deficient in the ATP-dependent activation of PLC and/or in the PEP-dependent enhancement of the ATP-dependent signal. These studies will define the role of ATP and PEP in IgE receptor-mediated activation of PLC and increase our understanding of the mechanism whereby this signal is transduced. In that the molecule(s) responsible for this effect may be specific for FcepsilonRI, this information has the potential to lead to novel pharmacologic agents for the prevention of immediate hypersensitivity reactions. On the other hand, if the role of PEP is eventually found to form the basis for a new paradigm of signal transduction for those receptors requiring aggregation for the initiation of a signal, these findings may have great impact on our understanding of antigen receptors on T cells and B cells as well as Fcgamma receptors on macrophages.