Regulation of CD23 Cleavage

描述（由申请人提供）：ige介导的过敏性哮喘影响1000万美国人。过敏性哮喘发作是由暴露于引起支气管收缩的过敏原引起的，通过给予β -2-肾上腺素能受体(（2AR）激动剂放松细支气管周围的平滑肌细胞来缓解。肺中的其他细胞表达（2AR），包括产生IgE的B淋巴细胞。高水平的IgE转化为更严重的过敏性哮喘症状。我们的实验室已经报道（2AR）刺激激活的B细胞会增加IgE转录率。(2AR的天然配体是神经递质去甲肾上腺素，它也与过敏性哮喘发作的严重程度有关。如果IgE水平与哮喘反应的严重程度有关，如果B细胞上的（2AR）刺激会增加IgE，那么确定介导这种增加的机制将是重要的。IgE水平受膜CD23 （mCD23）裂解成可溶性CD23 （sCD23）的调控，这两种蛋白分别负向或正向调节IgE的产生。我们的实验室确定了2AR诱导的细胞质CD23和sCD23总量的增加，而mCD23保持不变，这表明调控mCD23切割的机制可能是通过2AR刺激B细胞后激活的信号中间体来靶向的。将mCD23切割成sCD23的酶属于a崩解素和金属蛋白酶（ADAMs）家族，当ADAMs活跃时，其功能是增加IgE的正可溶性调节因子，同时保持负膜调节因子不变。虽然ADAM10被报道为主要的分泌酶，但我们的初步数据显示，在激活后的B细胞中，adam8、10和28的水平升高，但在伴随的（2AR）刺激后，只有adam8和28的水平进一步升高。在本提案中概述的实验中，我们将验证（2AR）刺激B细胞增加sCD23/mCD23的比例以及通过调节特定ADAMs的水平和/或蛋白水解活性而产生的IgE水平的假设。验证这一假设的意义在于，这些数据将阐明B细胞上的（2AR）刺激参与调节IgE水平的机制，从而在B细胞中确定新的药物靶点，防止激动剂活性过度产生IgE，而不干扰其他细胞上的激动剂活性，从而缓解过敏性哮喘症状。

DESCRIPTION (provided by applicant): IgE-mediated allergic asthma affects 10 million Americans. An allergic asthma attack is triggered by exposure to allergens that cause bronchoconstriction, which is relieved by the administration of a beta-2-adrenergic receptor ((2AR) agonist to relax smooth muscle cells surrounding the bronchioles. Other cells in the lung express the (2AR, including B lymphocytes that produce IgE. High levels of IgE translate into more severe allergic asthma symptoms. Our laboratory has reported that (2AR stimulation on an activated B cell increases the rate of IgE transcription. The natural ligand for the (2AR is the neurotransmitter norepinephrine, which is also associated with the severity of allergic asthma attacks. If the level of IgE is associated with the severity of an asthmatic response and if (2AR stimulation on a B cell increases IgE, it will be important to identify the mechanism that mediates this increase. IgE levels are regulated by the cleavage of membrane CD23 (mCD23) to soluble CD23 (sCD23), which, respectively, regulate IgE production negatively or positively. Our laboratory determined that there was a (2AR-induced increase in total cytoplasmic CD23 and sCD23, while mCD23 remained constant, suggesting that the mechanism involved in the regulation of mCD23 cleavage may be targeted by signaling intermediates activated after (2AR stimulation on a B cell. The enzymes that cleave mCD23 to sCD23 belong to a family of A Disintegrin And Metalloproteinases (ADAMs), which, when active, function to increase the positive soluble regulator of IgE, while keeping the negative membrane regulator constant. Although ADAM10 is reported to be the primary sheddase, our preliminary data show that the levels of ADAMs 8,10, and 28 increase in a B cell after activation, but that only the levels of ADAMs 8 and 28 increase further after concomitant (2AR stimulation. In experiments outlined in this proposal, we will test the hypothesis that (2AR stimulation on a B cell increases the ratio of sCD23/mCD23 and the subsequent level of IgE produced by regulating either the level and/or proteolytic activity of specific ADAMs. The significance of testing this hypothesis is that the data will elucidate a mechanism by which (2AR stimulation on a B cell participates in regulating the level of IgE, thus identifying novel drug targets in a B cell that would prevent agonist activity to overproduce IgE, without interfering with agonist activity on other cells that would relieve allergic asthma symptoms. PUBLIC HEALTH RELEVANCE: The current treatment for allergic asthma symptoms is to administer a beta-2 adrenergic receptor ((2AR) agonist drug, which binds to the (2AR expressed on bronchiole smooth muscle cells to cause them to relax, thus relieving bronchoconstriction. However, these agonists stimulate the (2AR on other cells, such as B cells to increase the level of IgE produced. Because the level of IgE is associated with the severity of allergic asthma symptoms, it will be important to identify the mechanism by which the 2(AR on a B cell increases IgE and if this mechanism is different from that used to relax bronchiole smooth muscle.