RabGEF1 in MyD88 signaling, skin immunity, and atopic dermatitis

 描述(申请人提供)：该项目的长期目标是了解某些角质形成细胞功能失调，通过改变细胞与TE皮肤微生物群的相互作用，如何损害表皮屏障功能，导致类似特应性皮炎(AD)的特征和高血清IgE水平的发展。小鼠RabGEF1被发现是肥大细胞激活的负调节因子，全球范围内RabGEF1缺陷的小鼠迅速发展为AD样皮肤[病理学]。然而，在小鼠角质形成细胞中有条件地删除Rabgef1足以推动AD样皮肤[病理]和高水平血清IgE的发展(正如在AD患者中也可以看到的那样)。此外，在RabGEF1基因缺陷小鼠中观察到的严重皮肤病严重依赖于角质形成细胞固有的MyD88表达，MyD88是一种通过几个Toll样受体(TLRs)介导信号的适配器分子。[RabGEF1蛋白]在AD患者皮损中的表达显著低于正常皮肤，而MYD88在AD患者皮损中的表达显著高于正常皮肤。由于皮肤持续暴露在TLR配体丰富来源的微生物中，我们将评估当角质形成细胞缺乏RabGEF1时，皮肤微生物群和角质形成细胞TLR在多大程度上有助于MyD88依赖的AD样皮肤[病理]。我们将使用RabGEF1基因缺陷的小鼠和人类角质形成细胞在体外分析RabGEF1调控MyD88依赖的信号通路的分子机制。最后，我们将评估角质形成细胞限制的RabGEF1表达的[全部或部分]减少如何通过皮肤影响全身对变应原的敏化，以及随后在远处器官(如肺)发生过敏性炎症的情况。我们提出了三个特定的目标来检验一般假设：以特应性皮炎为特征的皮肤病理的发展，以及血清IgE的升高，反映了RabGEF1通过下调MyD88依赖的角质形成细胞信号启动的途径来维持皮肤[屏障和免疫]功能的能力。目的1：明确MyD88、Toll样受体(TLRs)和皮肤微生物区系在角质形成细胞特异性Rabgef1缺失诱导的AD样皮肤[病理]中的作用。目的：探讨RabGEF1负性调节角质形成细胞MyD88依赖的功能反应和信号转导的机制。目的：探讨角质形成细胞中RabGEF1缺陷影响皮肤对过敏原的敏感性和特应性进行症发生的机制。这个项目将阐明由于RabGEF1减少而导致的角质形成细胞功能的内在损害如何有助于AD样皮肤[病理学]。最终，从事这样的工作可能会发现预防或治疗AD以及其他特应性或炎症性疾病的新的治疗靶点。

 DESCRIPTION (provided by applicant): The long-term goal of this project is to understand how the dysregulation of certain keratinocyte functions, by altering the cells' interactions with te skin microbiome, can impair epidermal barrier function, leading to features resembling those of atopic dermatitis (AD) and the development of high serum levels of IgE. Mouse RabGEF1 was discovered as a negative regulator of mast cell activation, and mice globally deficient in RabGEF1 rapidly develop AD-like skin [pathology]. However, conditional deletion of Rabgef1 specifically in mouse keratinocytes is sufficient to drive AD-like skin [pathology] and the development of high levels of serum IgE (as is also seen in AD patients). Moreover, the severe skin disease observed in RabGEF1- deficient mice critically depends on keratinocyte-intrinsic expression of MyD88, an adaptor molecule that mediates signaling by several Toll-like receptors (TLRs). [Expression of RabGEF1 protein] is markedly decreased in lesional skin from patients with AD as compared to healthy skin, whereas MYD88 mRNA expression is significantly increased in lesional skin specimens from AD patients. Since skin is continuously exposed to microorganisms that are a rich source of TLR ligands, we will evaluate to what extent the skin microbiome and keratinocyte TLRs can contribute to the MyD88-dependent AD-like skin [pathology] observed when keratinocytes lack RabGEF1. We will use RabGEF1-deficient mouse and human keratinocytes to analyze in vitro the molecular mechanisms by which RabGEF1 regulates MyD88-dependent signaling pathways. Finally, we will assess how keratinocyte-restricted [complete or partial] reductions in RabGEF1 expression can influence systemic sensitization to allergens via the skin, with the later development of allergic inflammation in distant organs such as the lung. We propose three specific aims to test the General Hypothesis: The development of skin pathology with features of atopic dermatitis, and elevated serum IgE, in RabGEF1-deficient mice reflects the ability of RabGEF1 to maintain skin [barrier and immune] functions by down-regulating pathways initiated by MyD88-dependent signaling in keratinocytes. Aim 1: Define the contributions of MyD88, Toll-like receptors (TLRs), and the skin microflora in the AD-like skin [pathology] induced by keratinocyte-specific Rabgef1 deletion in vivo. Aim 2: Determine the mechanisms by which RabGEF1 negatively regulates MyD88-dependent functional responses and signaling in keratinocytes. Aim 3: Determine the mechanisms by which RabGEF1 deficiency in keratinocytes influences skin sensitization to allergens and the development of the atopic march. This project will clarify how an intrinsic impairment in keratinocyte function due to diminished RabGEF1 can contribute to AD-like skin [pathology]. Ultimately, pursuing such work may enable the discovery of novel therapeutic targets for the prevention or treatment of AD and perhaps other atopic or inflammatory disorders.