TGF-β signaling and regulation: Elucidating molecular mechanisms and pathogenic functions of the ‘co-receptor’ Cripto-1 and the receptor BMPRII

项目总结 转化生长因子-β家族蛋白对人类健康至关重要。它们调节分化、增殖和 正常细胞生理中的动态平衡，但突变或异常表达与破坏性 疾病，包括癌症和肺动脉高压。发现靶向的治疗方法 转化生长因子-β家族蛋白是当务之急，将对人类健康产生重大影响。然而，识别 治疗一直很困难，因为转化生长因子-β家族蛋白的生理和病理活性 是定义不清的。对转化生长因子-β家族作用的深刻分子理解是克服这些问题的关键 障碍。因此，该实验室的首要目标是确定转化生长因子-β家族信号是如何调节的，并 将我们的发现与生理和病理过程联系起来。我们混合了结构生物学的工具， 生物化学和细胞生物学。在这里，我们有两个目标。在目标1中，我们将验证新建立的 CRIPTO-1家族共受体识别配体的机制及膜锚定受体的作用 和癌症中的可溶性Cripto-1。CRIPTO-1是一种膜锚定的EGF-cfc家族“共受体”。 促进肿瘤进展。它可以增强和抑制转化生长因子-β家族信号转导。但是Cripto-1是如何 调解这些对立活动的原因尚不清楚。我们最近的研究提出了一种机制。CRIPTO-1区块 转化生长因子-β家族配体与受体的结合。因此，可溶性形式抑制了信号转导。但是膜锚定的 CRIPTO-1增强信号转导，促进肿瘤发生。我们假设膜锚定的Cripto-1 在细胞表面捕获配体，并将其引导到内吞体内，以增强信号和致癌作用 激活。阐明CRIPTO-1/EGF-CFC的配体捕获和致癌激活机制 揭示针对癌症中Cripto-1的表位和模式。在目标2中，我们将确定配体结合 I型转化生长因子-β家族受体BMPRII的决定因素和建立配体的功能后果 BMPRII介导的信号和PAH的结合竞争。转化生长因子-β家族信号通过SMAD转导 转录因子。在PAH中，BMPRII介导的Smad1/5/8信号通路减少。至于是如何做到的，目前还不清楚。 我们最近的发现提供了一条线索。我们发现，受Cripto-1或其同源基因调控的配体存在秘密结合 具有高亲和力的BMPRII。到目前为止，BMPRII被认为是BMPs的低亲和力受体，BMPs是BMPs的一个亚类 转化生长因子-β家族配体。我们还发现，高亲和力配体通过以下方式抑制BMP依赖的Smad1/5/8信号 竞争受体结合。我们假设CRIPTO-1/隐蔽配体抑制BMPRII介导的 通过与BMP竞争BMPRII结合，在PAH中传递Smad1/5/8信号。证明了捆绑- 竞争促进多环芳烃表型和识别与BMPRII接触可能导致的配体表位 开发阻止高亲和力BMPRII配体与低亲和力BMP竞争的抑制剂，以及 从而有助于BMPRII介导的Smad1/5/8信号在PAH中的恢复。成功完成这些研究 可能有助于为在癌症中靶向Cripto-1和恢复PAH的BMPRII功能开辟新的途径。

PROJECT SUMMARY TGF-β family proteins are critically important for human health. They regulate differentiation, proliferation and homeostasis in normal cell physiology, but mutations or abnormal expression are associated with devastating diseases, including cancers, and Pulmonary Arterial Hypertension (PAH). Discovering therapeutics that target TGF-β family proteins is an urgent priority and will have a great impact on human health. However, identifying therapeutics has been difficult, because the physiological and pathological activities of TGF-β family proteins are poorly defined. A profound molecular understanding of TGF-β family action is essential to overcome these obstacles. Thus, the overarching goal of the lab is to determine how TGF-β family signaling is regulated and to link our findings with physiological and pathological processes. We blend tools of structural biology, biochemistry and cell biology. Here, we have two aims. In Aim 1 we will validate the newly established mechanism of ligand recognition by Cripto-1 family co-receptors and examine the roles of membrane-anchored and soluble Cripto-1 in cancers. Cripto-1 is a membrane-anchored, EGF-CFC family `co-receptor' that promotes tumor progression. It can both potentiate and inhibit TGF-β family signaling. But how Cripto-1 mediates these opposing activities is not clear. Our recent studies suggest a mechanism. Cripto-1 blocks binding of TGF-β family ligands to receptors. Thus, a soluble form inhibited signaling. But membrane-anchored Cripto-1 potentiated signaling and promoted tumorigenesis. We hypothesize that membrane-anchored Cripto-1 captures ligands at the cell surface and directs ligands into endosomes for signal potentiation and oncogenic activation. Elucidating the Cripto-1/EGF-CFC mechanism of ligand capture and oncogenic activation could reveal epitopes and modalities to target Cripto-1 in cancers. In Aim 2 we will identify the ligand binding determinants of the `type II' TGF-β family receptor BMPRII and establish functional consequences of ligand binding-competition for BMPRII mediated signaling and PAH. TGF-β family signals are transduced via SMAD transcription factors. In PAH, BMPRII mediated SMAD1/5/8 signaling is reduced. Just how is not understood. Our recent findings offer a clue. We discovered that ligands regulated by Cripto-1 or its homolog Cryptic bind BMPRII with high affinity. Until now, BMPRII was believed to be a low affinity receptor for BMPs, a subclass of TGF-β family ligands. We also found that high affinity ligands inhibit BMP dependent SMAD1/5/8 signaling by competing for receptor binding. We hypothesize that Cripto-1/Cryptic ligands suppress BMPRII mediated SMAD1/5/8 signaling in PAH by competing with BMPs for BMPRII binding. Demonstrating that binding- competition promotes PAH phenotypes and identifying epitopes on ligands that contact BMPRII could lead to development of inhibitors that prevent high affinity BMPRII ligands from competing with low affinity BMPs, and thus could help restore BMPRII mediated SMAD1/5/8 signaling in PAH. Successful completion of these studies could help open new avenues for targeting Cripto-1 in cancers and for restoring BMPRII function in PAH.