Novel Mechanisms of C-Kit Regulation in Mast Cells

描述（由申请方提供）：肥大细胞活化在哮喘和过敏中起关键的病理生理作用。肥大细胞活化的作用也在多发性硬化症、类风湿性关节炎和冠状动脉疾病中被描述。然而，最近的研究挑战了肥大细胞激活的病理作用的教条，证明了其在对病原菌的先天免疫的早期阶段的突出作用。这些观察使我们对肥大细胞生物学的理解比以往任何时候都更加重要。虽然几种细胞因子影响肥大细胞的生长、存活和成熟，但干细胞因子（SCF）及其通过酪氨酸激酶受体的相互作用，c-Kit对于正常肥大细胞发育和功能是必需的。缺乏c-Kit表达的小鼠缺乏肥大细胞，并表现出对诱导的细菌感染的死亡率增加。因此，尽管已经证明了c-Kit和IgE受体启动的信号在调节肥大细胞的正常发育和功能中的重要作用，但是对调节这些过程的这些受体下游的信号传导途径知之甚少。鉴定通过这些受体参与调节肥大细胞发育和功能的关键细胞内信号传导分子和途径将有助于设计用于治疗肥大细胞疾病的特异性分子疗法，包括与c-Kit的功能获得性突变相关的人肥大细胞增多症、慢性炎症、过敏以及用于促进对细菌感染的免疫。我们的长期目标是了解控制肥大细胞在细胞因子受体和免疫受体下游功能的信号传导机制。本申请的目的是确定SHIP磷酸酶、林恩Src家族激酶和IA类PI-3激酶的p85调节亚基（a和B）如何相互作用以调节肥大细胞分化、生长/存活以及细胞因子产生和脱粒。本申请的中心假设是，林恩激酶对肥大细胞中SHIP磷酸酶的活化至关重要，该假设是基于我们的初步数据制定的。在不存在SHIP磷酸化（由于缺乏林恩表达）的情况下，肥大细胞表现出对SCF诱导的存活、生长和分化以及增强的IgE受体诱导的脱粒和细胞因子产生的超敏反应。这些表型是由于PI-3激酶/Akt通路的过度活化。此外，p85 ct和p85| IA类PI-3激酶的3个调节亚基在调节肥大细胞功能中起着数量上不同的作用。这些差异是由于p85 a与p85（p85）中存在独特的氨基末端序列所致|3）。我们提出的研究将提供独特的见解，在体内的生理意义之间的相互作用的SHIP，林恩和p85调节亚基IA类PI-3激酶调节肥大细胞生物学的各个方面。

DESCRIPTION (provided by applicant): Mast cell activation plays a critical pathophysiologic role in asthma and allergy. A role for mast cell activation has also been described in multiple sclerosis, rheumatoid arthritis and coronary artery disease. However, recent studies challenge the dogma of a pathological role for mast cell activation, demonstrating its prominent role in the early phases of innate immunity to pathogenic bacteria. These observations make our understanding of mast cell biology more crucial than ever. While several cytokines influence the growth, survival, and maturation of mast cells, stem cell factor (SCF) and its interaction via the tyrosine kinase receptor, c-Kit is essential for normal mast cell development and function. Mice deficient in the expression of c-Kit lack mast cells and exhibit enhanced mortality to induced bacterial infections. Thus, although an important role for c-Kit and IgE receptor initiated signals in regulating normal development and function of mast cells has been demonstrated, the signaling pathways downstream from these receptors that regulate these processes are poorly understood. Identification of key intracellular signaling molecules and pathways involved in regulating the development and function of mast cells via these receptors will facilitate the design of specific molecular therapies for the treatment of mast cell disorders, including human mastocytosis associated with gain-of-function mutations of c-Kit, chronic inflammation, allergy as well as for promoting immunity to bacterial infections. Our long-range goal is to understand the signaling mechanism(s) that control mast cell functions downstream from cytokine receptors as well as immunoreceptors. The objective of this application is to determine how SHIP phosphatase, Lyn Src family kinase and p85 regulatory subunits (a and b) of class IA PI-3Kinase interact to regulate mast cell differentiation, growth/survival as well as cytokine production and degranulation. The central hypothesis of this application, which has been formulated on the basis of our preliminary data, is that Lyn kinase is critical for the activation of SHIP phosphatase in mast cells. In the absence of SHIP phosphorylation (due to lack of Lyn expression) mast cells demonstrate hypersensitivity to SCF-induced survival, growth and differentiation as well as enhanced IgE receptor induced degranulation and cytokine production. These phenotypes are due to hyperactivation of the PI-3Kinase/Akt pathway. Furthermore, p85ct and p85|3 regulatory subunits of class IA PI-3Kinase play quantitatively distinct roles in regulating mast cell functions. These differences are due to the presence of unique amino terminal sequences in p85a vs (p85|3). Our proposed studies will provide unique insights into the physiologic significance of the in vivo interactions between SHIP, Lyn and p85 regulatory subunits of class IA PI-3Kinase in regulating all aspects of mast cell biology.