ROLE OF BAG2 AND SHP2 IN HEMATOPOIETIC SIGNALLING

BAG2 和 SHP2 在造血信号传导中的作用

• 批准号: 6293951
• 负责人: BENJAMIN G. NEEL
• 金额: $ 41.24万
• 依托单位: BETH ISRAEL DEACONESS MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-03-15 至 2005-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6293951
• 关键词: biological signal transduction; cell differentiation; cell proliferation; colony stimulating factor; embryonic stem cell; enzyme activity; gene expression; gene targeting; genetic regulation; genetic transcription; genetically modified animals; hematopoiesis; hematopoietic stem cells; laboratory mouse; macrophage; mitogen activated protein kinase; mutant; phosphatidylinositol 3 kinase; phosphorylation; polymerase chain reaction; protein binding; protein tyrosine kinase; protein tyrosine phosphatase; southern blotting; tissue /cell culture

Many important biological processes are regulated by tyrosyl phosphorylation, which is controlled by the opposing actions of protein-- tyrosine kinases (PTKs) and protein-tyrosine phosphatases (PTPs). Abnormal regulation of these pathways can lead to diseases such as cancer. A complete understanding of cellular and whole organism regulation by tyrosyl phosphorylation requires defining how specific PTKs and PTPs interact. Such understanding may lead to the development of new, more specific therapeutic reagents for treating human disease. The long range goal of this research program is to understand the biological functions and mechanism of action of the SH2 domain-containing tyrosine phosphatase SHP2 in hematopoietic cells. Previous studies by several laboratories, including our own, established SHP2 as a vital component of signaling pathways downstream of cytokine receptors, hematopoietic growth factor receptors and multi- chain immune recognition receptors. These studies suggested that a 97kD phosphotyrosyl protein was a major target/regulator of SHP2 action, but the identity of this protein and its functions had remained unclear. During the initial funding period, we identified, purified and cloned p97. p97 is a relative of Gab1 and Drosophila Dos, a regulator of the fly homolog of SHP-2; thus, we renamed p97 as Gab2. Analyses of the effects of wild type and mutant versions of Gab2 suggest that it is a key regulator of cytokine signal transduction and also participates in signaling downstream of other types of hematopoietic cell receptors. Our studies establish that SHP2 acts at more than one step in cytokine receptor signal transduction: one requires Gab2 binding and the other is Gab-2 independent. The Ciab2-independent pathway is required for MAP kinase activation, whereas Gab2, acting via SHP2, regulates a novel signaling pathway downstream of/or parallel to MAP kinase activation but upstream of cytokine-induced gene expression. Our recent studies show that Gab2 is recruited to cytokine receptors via a novel complex involving Shc, and then provides the major route to PI-3 kinase activation for those receptors that do not bind PI3K directly. We will elucidate the details of the Shc/Gab2 pathway in cytokine signaling. and determine what other pathways are regulated by Gab2/PI3K complexes. Next, we will define how SHP2 regulates MAP kinase activation in a Gab-2- independent manner and how the Gab2/SHP2 complex regulates immediate early gene transcription. We will characterize the hematopoietic effects of "true-null" SHP2 knockout mice and Gab2-/- mice to determine the physiological function of these molecules in vivo. These studies should yield new insights into how tyrosyl phosphorylation is controlled. clarify how specific PTPs contribute to regulation, and identify a new signaling pathway regulating cytokine-induced gene expression. Since abnormal regulation of cytokine signaling is implicated in leukemogenesis and some carcinomas, our studies may also suggest new targets for therapeutic intervention in human neoplastic disease.

许多重要的生物过程都受到酪氨酰磷酸化的调节，酪氨酰磷酸化是由蛋白质酪氨酸激酶（PTK）和蛋白质酪氨酸磷酸酶（PTP）的相反作用控制的。这些途径的异常调节可能导致癌症等疾病。要完整了解酪氨酰磷酸化对细胞和整个生物体的调节，需要定义特定 PTK 和 PTP 如何相互作用。这种理解可能会导致开发新的、更具体的治疗试剂来治疗人类疾病。该研究计划的长期目标是了解造血细胞中含有SH2结构域的酪氨酸磷酸酶SHP2的生物学功能和作用机制。包括我们自己的实验室在内的多个实验室之前的研究表明，SHP2 是细胞因子受体、造血生长因子受体和多链免疫识别受体下游信号通路的重要组成部分。这些研究表明 97kD 磷酸酪氨酰蛋白是 SHP2 作用的主要靶标/调节因子，但该蛋白的身份及其功能仍不清楚。在最初的资助期间，我们鉴定、纯化并克隆了 p97。 p97 是 Gab1 和果蝇 Dos 的亲戚，是果蝇 SHP-2 同源物的调节因子；因此，我们将 p97 重命名为 Gab2。对 Gab2 野生型和突变型的影响的分析表明，它是细胞因子信号转导的关键调节因子，并且还参与其他类型造血细胞受体的下游信号传导。我们的研究表明，SHP2 在细胞因子受体信号转导中发挥不止一个步骤：一个需要与 Gab2 结合，另一个不依赖于 Gab-2。 MAP 激酶激活需要不依赖于 Ciab2 的途径，而 Gab2 通过 SHP2 发挥作用，调节 MAP 激酶激活下游/或平行的新信号传导途径，但位于细胞因子诱导的基因表达的上游。我们最近的研究表明，Gab2 通过一种涉及 Shc 的新型复合物被招募到细胞因子受体，然后为那些不直接结合 PI3K 的受体提供 PI-3 激酶激活的主要途径。我们将阐明细胞因子信号转导中 Shc/Gab2 途径的细节。并确定哪些其他途径受 Gab2/PI3K 复合物调节。接下来，我们将定义 SHP2 如何以不依赖于 Gab-2 的方式调节 MAP 激酶激活，以及 Gab2/SHP2 复合物如何调节即早期基因转录。我们将表征“真无效”SHP2 敲除小鼠和 Gab2-/- 小鼠的造血作用，以确定这些分子在体内的生理功能。这些研究应该对酪氨酰磷酸化的控制方式产生新的见解。阐明特定 PTP 如何参与调节，并确定调节细胞因子诱导的基因表达的新信号通路。由于细胞因子信号传导的异常调节与白血病发生和某些癌症有关，因此我们的研究也可能为人类肿瘤疾病的治疗干预提供新的靶点。