Sphingosine-1 phosphate in mast and airway smooth cell

描述(申请人提供)：高亲和力的IgE受体FcepsilonRI是哮喘的核心，哮喘是一种慢性疾病，其特征是呼吸道炎症和对促进呼吸道收缩和喘息的收缩刺激的高反应性。FcepsilonRI介导的信号系统中的一个新成员是鞘氨醇激酶(SPHK)的激活，导致由鞘氨醇产生的新的鞘氨醇介体-1-磷酸鞘氨醇(SPP)。在节段性抗原攻击后，哮喘患者的呼吸道SPP分泌显著增加，将这种鞘脂添加到过敏反应期间释放的各种介质中。 肥大细胞是免疫球蛋白E介导的变态反应的主要效应细胞。在这个方案中，我们将确定SF2及其受体的作用，并验证SPHK在肥大细胞FcepsilonRI启动的信号级联激活中起关键作用的假设，该假说是通过调节中和的鞘磷脂代谢物、鞘氨醇和SPP的平衡来实现的。因此，SPHK不同亚型的强制表达，导致SPP的产生(和分泌)和鞘氨醇水平的降低，应该促进肥大细胞的激活，反之，由于抑制SPHK的特定亚型而减少SPP的形成和增加鞘氨醇，无论是通过特异性阻断其内源性表达的基因操作，显性负突变或药理学，都应该抑制肥大细胞的激活，并防止下游事件，如脱颗粒，过敏介质的分泌和细胞因子和趋化因子的诱导。 我们还将研究FcepsilonRI和GPCRs之间交叉通信的新机制概念，即IgE触发刺激SPHK导致SPP的形成和分泌增加，进而反式激活肥大细胞GPCRs的SPP、EDG-5和/或EDG-1，导致对肥大细胞激活重要的下游信号的放大。 我们的中心假说认为，SPP是肥大细胞释放的调节居民呼吸道细胞功能的重要介质。因此，我们还将研究SPP及其受体在调节人类气道平滑肌细胞收缩和增殖中的作用，促进支气管收缩和气道重塑的过程，这在哮喘的病理生物学中至关重要。增加对SPHKs、SPP及其受体调控的细胞通路的了解，最终导致哮喘反应，可能有助于开发针对强大的鞘磷脂介质SPP的新的治疗策略。

DESCRIPTION (provided by applicant): The high affinity IgE receptor FcepsilonRI is central to asthma, a chronic disease characterized by airway inflammation and hyperresponsiveness to contractile stimuli that promote airway constriction and wheezing. A newly recognized addition to the repertoire of FcepsilonRI-mediated signaling systems is the activation of sphingosine kinase (SPHK) leading to the generation of the novel sphingolipid mediator, sphingosine-1-phosphate (SPP) from sphingosine. SPP secretion is significantly elevated in the airways of asthmatics after segmental antigen challenge, adding this sphingolipid to the variety of mediators that are released during an allergic reaction. Mast cells are known to be the main effector cells in the elicitation of the IgE-mediated allergic response. In this proposal, we will determine the role of SF2 and its receptors and examine the hypothesis that SPHK is pivotal to the activation of signaling cascades initiated at the FcepsilonRI in mast cells by modulating the balance of the counteracting sphingolipid metabolites, sphingosine and SPP. Hence, enforced expression of different isoforms of SPHK, resulting in SPP generation (and secretion) and reduction of sphingosine levels should enhance mast cell activation and conversely, decreased SPP formation and increased sphingosine due to inhibition of specific isoforms of SPHK, either by genetic manipulations to specifically block their endogenous expression, dominant negative mutants or pharmacologically, should inhibit mast cell activation and prevent downstream events, such as degranulation, secretion of allergic mediators and induction of cytokines and chemokines. We will also examine a new mechanistic concept for cross communication between FcepsilonRI and GPCRs, whereby IgE triggering stimulates SPHK resulting in increased formation and secretion of SPP, which in turn transactivates the mast cell GPCRs for SPP, EDG-5 and/or EDG-1, leading to amplification of downstream signals important for mast cell activation. Our central hypothesis states that SPP is an important mediator released by mast cells to regulate resident airway cell function. Hence, we will also examine the role of SPP and its receptors in modulation of human airway smooth muscle cell contraction and proliferation, processes that promote bronchoconstriction and airways remodeling, critically important in the pathobiology of asthma.Increased understanding of cellular pathways regulated by SPHKs, SPP, and its receptors which culminate in asthmatic responses, may help in the development of novel therapeutic strategies aimed specifically at the potent sphingolipid mediator SPP.