Growth Hormone Regulation of SH2-B

描述（由申请人提供）：JAK家族酪氨酸激酶作为生长激素（GH）受体（GHR）和细胞因子受体超家族许多其他成员的受体相关信号分子的鉴定是我们理解GH作用的细胞基础的重要一步。在GH结合后，GHR相关的JAK 2被激活并磷酸化JAK 2本身和GHR内的酪氨酸。这些磷酸酪氨酸形成多种信号分子的结合位点，这些信号分子被JAK 2-GHR复合物募集和/或激活，启动导致对GH的多种生理反应的信号通路。虽然一些信号分子结合到GHR内的磷酸酪氨酸，但对结合到JAK 2内的磷酸酪氨酸的信号分子知之甚少，尽管JAK 2内存在49个酪氨酸。SH 2-B是少数已知的JAK 2结合蛋白之一。响应于GH，SH 2-B与JAK 2结合，被JAK 2磷酸化并增强GH诱导的JAK 2活化。SH 2-B独立于其激活JAK 2的能力，增强了GH对肌动蛋白细胞骨架和细胞运动的调节。最后，SH 2-B穿梭于细胞质和细胞核之间，并增强叉头转录因子的核输出。该建议的目的是检验以下假设：SH 2-B是一种多功能衔接/支架蛋白，可增强JAK 2的GH活化，增强肌动蛋白细胞骨架的GH调节，并调节细胞核中的GH反应。目的1探讨SH 2-B激活JAK 2的机制。目的2将进一步明确SH 2-B在GH介导的肌动蛋白细胞骨架变化中的作用。涉及肌动蛋白细胞骨架调节的多种蛋白质已被初步鉴定为SH 2-Bbeta结合蛋白。将确认它们与SH 2-B的结合，并确定SH 2-B对其功能和亚细胞位置的影响。目的3将研究SH 2-B是否通过将蛋白质穿梭于细胞核内外来调节转录。最后，目标4将使用多种蛋白质去除技术来鉴定SH 2-B在GH作用中的生理作用，包括siRNA、SH 2-B-/-小鼠和来自SH 2-B -/-小鼠的鼠胚胎成纤维细胞和组织。这些研究将深入了解SH 2-B在GH和其他细胞因子、激素和生长因子（例如干扰素-γ、胰岛素、神经生长因子）功能中的作用，这些因子也利用SH 2-B作为信号蛋白。这种认识与理解GH调节身体生长和代谢的机制有关，并且其它SH 2-B活化配体有助于预防和/或减轻多种疾病的症状，所述疾病包括多种癌症、糖尿病、多发性硬化症和免疫系统疾病。

DESCRIPTION (provided by applicant): Identification of JAK family tyrosine kinases as receptor-associated signaling molecules for growth hormone (GH) receptors (GHR) and the many other members of the cytokine receptor superfamily was a major step forward in our understanding of the cellular basis for GH actions. Upon GH binding, GHR-associated JAK2 is activated and phosphorylates tyrosines within JAK2 itself and GHR. These phosphotyrosines form binding sites for a variety of signaling molecules whose recruitment to and/or activation by JAK2-GHR complexes initiates the signaling pathways that lead to the diverse physiological responses to GH. While some signaling molecules bind to phosphotyrosines within GHR, little is known about the signaling molecules that bind to phosphotyrosines within JAK2, despite the presence of 49 tyrosines within JAK2. SH2-B is one of the few known JAK2 binding proteins. In response to GH, SH2-B binds to JAK2, is phosphorylated by JAK2 and enhances GH-induced activation of JAK2. Independent of its ability to activate JAK2, SH2-B enhances GH regulation of the actin cytoskeleton and cell motility. Finally, SH2-B shuttles between the cytoplasm and the nucleus, and enhances the nuclear export of forkhead transcription factors. The aim of this proposal is to test the hypothesis that SH2-B is a multi-functional adapter/scaffolding protein that enhances GH activation of JAK2, enhances GH regulation of the actin cytoskeleton and regulates GH responses in the nucleus. Aim 1 lexamines the mechanism by which SH2-B activates JAK2. Aim 2 will further define the role of SH2-B in GH-mediated changes in the actin cytoskeleton. Multiple proteins implicated in the regulation of the actin cytoskeleton have been tentatively identified as SH2-Bbeta binding proteins. Their binding to SH2-B will be confirmed and the effect of SH2-B on their function and subcellular location determined. Aim 3 will examine whether SH2-B regulates transcription by shuttling proteins into or out of the nucleus. Finally, Aim 4 will use a variety of protein depletion techniques to identify the physiological role for SH2-B in GH action, including siRNA, SH2-B" mice, and murine embryo fibroblasts and tissues from SH2-B -/- mice. These studies will provide insight into the role of SH2-B in the function of GH and other cytokines, hormones and growth factors (e.g. interferon-gamma, insulin, nerve growth factor) that also utilize SH2-B as a signaling protein. Such insight is relevant to understanding the mechanism(s) by which GH regulates body growth and metabolism, and other SH2-B activating ligands contribute to, prevent and/or alleviate symptoms of a variety of diseases including various cancers, diabetes, multiple sclerosis, and diseases of the immune system.