Negative Regulation of Signal Transduction by G-CSF

G-CSF 对信号转导的负调控

• 批准号: 6623659
• 负责人: FAN DONG
• 金额: $ 18.26万
• 依托单位: UNIVERSITY OF TOLEDO
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-02 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6623659
• 关键词: SDS polyacrylamide gel electrophoresis; antibody; biological signal transduction; carcinogenesis; cell differentiation; cell proliferation; colony stimulating factor; cytokine receptors; enzyme activity; flow cytometry; gel mobility shift assay; granulocyte; immunoprecipitation; leukemia; leukopoiesis; mutant; phosphorylation; protein structure function; protein tyrosine phosphatase; receptor binding; receptor expression; thin layer chromatography; western blottings

Binding of granulocyte colony-stimulating factor (G-CSF) to its cognate receptor results in activation of multiple signal transduction pathways that are critical for the regulation of granulopoiesis. How G-CSF-activated signaling events are downmodulated is largely unknown. Mutations in the G-CSF receptor gene leading to its C-terminal truncation have been reported in patients with acute myeloid leukemia (AML), providing the first clinical evidence for the involvement of abnormal cytokine receptors in human leukemia. Expression of the truncated receptors in hematopoietic cells results in enhanced cell proliferation and survival but impaired myeloid differentiation in response to G-CSF. The truncated receptors also mediate dramatically augmented and/or prolonged activation of Stats and Akt, which play crucial roles in regulating cell proliferation and survival. Interestingly, substitution of the three C-terminal tyrosine residues with phenylalanine leads to prolonged but not enhanced activation of Stats and Akt whereas deficiency of tyrosine phosphatase SHP-1 is associated with enhanced but not prolonged Stat activation by G-CSF. We hypothesize that the magnitude and duration of Stat and Akt activation by G-CSF are downregulated by distinct negative regulatory mechanisms and that the C-terminal region of the G-CSF receptor may contain critical subdomains implicated in interactions with the negative regulatory mechanisms. Two specific aims are proposed to test this hypothesis: (1) to define the C-terminal subdomain required for the downregulation of the magnitude of Stat activation and examine the mechanism by which SHP-1 exerts its negative effect on Stat activation; and (2) to identify the C-terminal tyrosine residues involved in the negative regulation of the duration of Stat and Akt activation by G-CSF and investigate the roles of negative regulatory molecules such as SHP-2 and SHIP in G-CSF receptor signaling. The proposed research will improve our understanding of the regulatory network of G-CSF signaling and the molecular mechanisms by which C- terminal truncation of the G-CSF receptor contribute to leukemogenesis.

粒细胞集落刺激因子(G-CSF)与其同源受体结合可激活多条信号转导通路，这些信号转导通路对粒细胞生成的调控至关重要。G-CSF激活的信号事件是如何下调的在很大程度上是未知的。在急性髓系白血病(AML)患者中发现G-CSF受体基因突变导致其C端截短，这为人类白血病中异常细胞因子受体的参与提供了第一个临床证据。在造血细胞中表达截短的受体可以促进细胞的增殖和存活，但会影响G-CSF对髓系细胞的分化。被截断的受体还显著增强和/或延长了Stats和Akt的激活，这两个基因在调节细胞增殖和生存方面发挥着关键作用。有趣的是，用苯丙氨酸取代三个C端酪氨酸残基会导致Stats和Akt的激活延长但不会增强，而酪氨酸磷酸酶SHP-1的缺失与G-CSF增强但不会延长Stat的激活有关。我们假设G-CSF激活Stat和Akt的幅度和持续时间受到不同的负性调节机制的下调，G-CSF受体的C末端区域可能包含与负性调节机制相互作用的关键亚域。为了验证这一假说，提出了两个具体的目标：(1)确定下调Stat激活幅度所需的C末端亚域，并研究SHP-1对Stat激活的负面影响机制；(2)鉴定参与G-CSF对Stat和Akt激活持续时间的负调控的C末端酪氨酸残基，并研究SHP-2和Ship等负调控分子在G-CSF受体信号转导中的作用。这项拟议的研究将提高我们对G-CSF信号调控网络的理解，以及G-CSF受体C端截短促进白血病发生的分子机制。