Regulation of CD23 Cleavage

描述(申请人提供)：免疫球蛋白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发的，通过注射β-2-肾上腺素能受体(2AR)激动剂来松弛细支气管周围的平滑肌细胞，这种情况得到缓解。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会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对激活的B细胞的刺激会增加IgE的转录速率。(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相关，如果B细胞上的2AR刺激增加了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)和可溶性CD23(SCD23)裂解的调节，后者分别负向或正向调节IgE的产生。我们的实验室发现，在(2AR)刺激B细胞后，胞浆总CD23和sCD23增加，而mCD23保持不变，这表明参与mCD23切割调控的机制可能是通过激活信号中间产物来实现的。将mCD23裂解为sCD23的酶属于A去整合素和金属蛋白水解酶(ADAMS)家族，当ADAMS被激活时，它的功能是增加IgE的正向可溶性调节因子，同时保持负膜调节因子的恒定。虽然ADAM10被报道是主要的脱落酶，但我们的初步数据显示，激活后B细胞中ADAMS 8、10和28的水平增加，但只有ADAM8和28的水平在伴随的(2AR)刺激后进一步增加。在这项提案中概述的实验中，我们将检验以下假设：(2AR刺激B细胞会增加sCD23/mCD23的比率，并通过调节特定ADAMS的水平和/或蛋白分解活性来产生随后的IgE水平。检验这一假说的意义在于，数据将阐明B细胞上的AR刺激参与调节IgE水平的机制，从而在B细胞中识别新的药物靶点，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。 公共卫生相关性：目前治疗过敏性哮喘症状的方法是应用一种β-2肾上腺素能受体(2AR)激动剂药物，该药物与表达在细支气管平滑肌细胞上的(2AR)结合，使其松弛，从而缓解支气管收缩。然而，这些激动剂刺激其他细胞上的(2AR)，如B细胞，以增加IgE产生的水平。由于IgE水平与过敏性哮喘症状的严重程度相关，因此确定B细胞上的2(AR)增加IgE的机制以及该机制是否不同于用于松弛细支气管平滑肌的机制将是重要的。

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.