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受体（GHR）和细胞因子受体超家族的许多其他成员的受体相关信号分子的鉴定是我们对生长激素作用的细胞基础的理解向前迈出的重要一步。GH结合后，GHR相关的JAK2被激活并磷酸化JAK2自身和GHR中的酪氨酸。这些磷酸酪氨酸形成了多种信号分子的结合位点，这些信号分子被JAK2-GHR复合物募集和/或激活，启动了导致对生长激素的各种生理反应的信号通路。虽然GHR中的一些信号分子与磷酸酪氨酸结合，但对于JAK2中与磷酸酪氨酸结合的信号分子知之甚少，尽管JAK2中存在49种酪氨酸。SH2-B是少数已知的JAK2结合蛋白之一。在GH的作用下，SH2-B与JAK2结合，被JAK2磷酸化，并增强GH诱导的JAK2活化。独立于激活JAK2的能力，SH2-B增强GH对肌动蛋白细胞骨架和细胞运动的调节。最后，SH2-B穿梭于细胞质和细胞核之间，增强叉头转录因子的核输出。本研究的目的是验证SH2-B是一种多功能适配器/支架蛋白的假设，它可以增强JAK2的GH激活，增强GH对肌动蛋白细胞骨架的调节，并调节细胞核中的GH反应。Aim 1研究SH2-B激活JAK2的机制。Aim 2将进一步确定SH2-B在gh介导的肌动蛋白细胞骨架变化中的作用。参与肌动蛋白细胞骨架调节的多种蛋白已初步确定为sh2 - bβ结合蛋白。将证实它们与SH2-B的结合，并确定SH2-B对它们的功能和亚细胞位置的影响。目的3将检查SH2-B是否通过将蛋白穿梭进出细胞核来调节转录。最后，Aim 4将使用多种蛋白质耗尽技术来确定SH2-B在GH作用中的生理作用，包括siRNA、SH2-B”小鼠、小鼠胚胎成纤维细胞和SH2-B -/-小鼠的组织。这些研究将深入了解SH2-B在生长激素和其他细胞因子、激素和生长因子（如干扰素- γ、胰岛素、神经生长因子）的功能中的作用，这些细胞因子、激素和生长因子也利用SH2-B作为信号蛋白。这种见解与理解GH调节身体生长和代谢的机制有关，以及其他SH2-B激活配体有助于预防和/或减轻各种疾病的症状，包括各种癌症、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.