LRP6 phosphorylation in Wnt/beta-catenin signaling

Wnt/β-连环蛋白信号传导中的 LRP6 磷酸化

• 批准号: 6913946
• 负责人: Xi He
• 金额: $ 29.49万
• 依托单位: BOSTON CHILDREN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2009-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6913946
• 关键词: RNA interference; SDS polyacrylamide gel electrophoresis; Xenopus; biological signal transduction; cadherins; cell surface receptors; genetic library; genetic screening; immunoprecipitation; phosphorylation; protein kinase; protein protein interaction; protein structure function; receptor expression; western blottings

DESCRIPTION (provided by applicant): Wnt signaling through the canonical a-catenin pathway controls cell fate determination and cell proliferation, and is essential for animal development. Defective Wnt/b-catenin signaling has been associated with human colorectal cancer, familial osteoporosis, and other diseases. Thus understanding Wnt/b-catenin signaling is highly relevant to human health. Wnt/b-catenin signaling is initiated by 2 distinct families of cell surface receptors. One (1) is a member of the Frizzled (Fz) family of serpentine receptors, and the other is a single transmembrane receptor of the LDL receptor related protein family, LRP5 or LRP6. How Wnt leads to the activation of these receptors is a critical but poorly understood issue. Dr. He's group showed that Fz and LRP5/6 form a Wnt-inducible co-receptor complex in vitro, and that LRP6 plays a key role in the signaling process. They recently discovered that phosphorylation likely underlies LRP6 activation. They found that a PPP(S/T)P motif, which is reiterated 5 times in the intracellular domain of LRP5/6, is essential for LRP6 signaling function. They demonstrated that phosphorylation of this PPP(S/T)P motif is required for signaling and for binding/recognition by Axin, a key scaffolding protein that regulates b-catenin stability. They further showed that Wnt induces LRP6 phosphorylation in vivo. These results suggest that Wnt activates transmembrane signaling via inducing LRP6 phosphorylation. In this application, 3 specific aims are designed to substantiate/extend this working model. (1) To characterize fully all five PPP(S/T)P motifs in LRP6 intracellular domain. Issues to be addressed include the function of these PPP(S/T)P motifs and whether their differential phosphorylation controls LRP6 signaling. (2) To investigate Axin interaction with the phosphorylated PPP(S/T)P motifs. The aim is to identify the Axin domain/module that recognizes PPP(S/T)P phosphorylation, and examine whether LRP6-Axin association alters the composition of the Axin complex, thereby governing b-catenin stability. (3) To identify kinase (or kinases) that phosphorylates the PPP(S/T)P motif. This aim is to investigate known kinases implicated in Wnt/a-catenin signaling for their potential roles in PPP(S/T)P phosphorylation and to isolate the PPP(S/T)P kinase or kinases via several complementary approaches. These experiments will significantly enhance the understanding of Wnt receptor activation and Wnt signal transduction in development and disease.

描述（由申请人提供）：通过经典α-连环蛋白途径的Wnt信号传导控制细胞命运决定和细胞增殖，并且对于动物发育至关重要。 Wnt/b-连环蛋白信号传导缺陷与人类结直肠癌、家族性骨质疏松症和其他疾病有关。因此，了解 Wnt/b-catenin 信号传导与人类健康高度相关。 Wnt/b-连环蛋白信号传导由 2 个不同的细胞表面受体家族启动。一 (1) 是蛇纹受体卷曲 (Fz) 家族的成员，另一个是 LDL 受体相关蛋白家族 LRP5 或 LRP6 的单一跨膜受体。 Wnt 如何导致这些受体的激活是一个关键但知之甚少的问题。何博士课题组证明Fz和LRP5/6在体外形成Wnt诱导的共受体复合物，并且LRP6在信号传导过程中发挥关键作用。他们最近发现磷酸化可能是 LRP6 激活的基础。他们发现PPP(S/T)P基序在LRP5/6的胞内结构域中重复5次，对于LRP6信号传导功能至关重要。他们证明，该 PPP(S/T)P 基序的磷酸化是 Axin 信号传导和结合/识别所必需的，Axin 是调节 b-连环蛋白稳定性的关键支架蛋白。他们进一步表明 Wnt 在体内诱导 LRP6 磷酸化。这些结果表明 Wnt 通过诱导 LRP6 磷酸化来激活跨膜信号传导。在此应用程序中，设计了 3 个具体目标来证实/扩展此工作模型。 (1) 全面表征 LRP6 胞内结构域中所有五个 PPP(S/T)P 基序。需要解决的问题包括这些 PPP(S/T)P 基序的功能以及它们的差异磷酸化是否控制 LRP6 信号传导。 (2) 研究 Axin 与磷酸化 PPP(S/T)P 基序的相互作用。目的是鉴定识别 PPP(S/T)P 磷酸化的 Axin 结构域/模块，并检查 LRP6-Axin 关联是否改变 Axin 复合物的组成，从而控制 β-连环蛋白的稳定性。 (3) 鉴定磷酸化 PPP(S/T)P 基序的激酶（或多种激酶）。该目的是研究与 Wnt/a-连环蛋白信号传导有关的已知激酶在 PPP(S/T)P 磷酸化中的潜在作用，并通过几种补充方法分离 PPP(S/T)P 激酶或激酶。这些实验将显着增强对发育和疾病中 Wnt 受体激活和 Wnt 信号转导的理解。