ROLE OF BETAGLYCAN IN INHIBIN ANTAGONISM OF ACTIVIN

Betaglycan 在激活素抑制素拮抗作用中的作用

• 批准号: 7537246
• 负责人: WYLIE W. VALE
• 金额: $ 35.02万
• 依托单位: SALK INSTITUTE FOR BIOLOGICAL STUDIES
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-12-01 至 2008-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7537246
• 关键词: Activins; Adrenal Gland Neoplasms; Affinity; Anterior Pituitary Gland; Binding; Binding Sites; Biochemical; Biological Models; Bone Morphogenetic Proteins; Cell Line; Cell physiology; Cells; Complex; Contraceptive methods; Development; Disease; Endocrine; Follicle Stimulating Hormone; Genes; Grant; In Vitro; Inhibin-beta Subunits; Knock-out; Knockout Mice; Mass Spectrum Analysis; Mediating; Mediation; Mediator of activation protein; Membrane; Messenger RNA; Modeling; Molecular; Mus; Phenotype; Pituitary Gland; Play; Process; Production; Protein Region; Protein-Serine-Threonine Kinases; Proteins; Recombinant Inhibin A; Recruitment Activity; Regulation; Role; Signal Transduction; Surface; System; TGF beta type III receptor; Techniques; Testing; Transforming Growth Factor beta; Variant; autocrine; base; cell type; crosslink; dimer; hepatic necrosis; human INHA protein; improved; in vivo; inhibin; inhibin receptor; member; paracrine; protein expression; reagent testing; receptor; reproductive; reproductive hormone; research study; response; sertoli cell

Activins and certain BMPs are members of the TGF-beta superfamily that regulate FSH production by the anterior pituitary. They and their receptors also have diverse endocrine, paracrine, and autocrine actions throughout the reproductive, endocrine and other systems and play key roles in development and in pathophysiologic processes. Inhibins oppose some, but not all actions of activin and are crucial for survival as illustrated by the lethal phenotype of inhibin alpha null mice, which suffer gonadal and adrenal tumors and liver necrosis. To exert cellular effects, activins (beta-beta dimers) bind their type II receptor serine kinases (ActRII or ActRIIB) and then recruit the type I receptor serine kinase (ALK4) to form active complexes that initiate downstream signaling. Inhibins (alpha-beta dimers) compete with activins for binding to ActRII but the inhibin/ActRII complexes do not recruit ALK4 or promote signaling. Inhibins are potent functional antagonists of activin yet the relatively low affinity of inhibins compared to activin for ActRII was not in keeping with a simple competition model. Thus other components were sought and during the past grant period we identified betaglycan (TGF-beta type III receptor) as a high affinity inhibin binding protein (co-receptor) that facilitates inhibin binding to ActRII and, thereby, greatly increases the potency of inhibin to antagonize activin signaling. In model systems we have demonstrated that inhibin can antagonize responses to some BMPs. Under Aim I, these findings will be extended to test if inhibins antagonize the effects of BMPs on pituitary cells. We will continue to characterize the binding interactions between inhibins, betaglycan, and the type II receptors, ActRII, ActRIIB and BMPRII. We will identify the betaglycan residues and regions required for inhibin binding and will produce minimized soluble betaglycan forms that will be used for biochemical and structural (with Project II) studies. Identification of the critical interactive surfaces and regions of these proteins will facilitate efforts to devise strategies for modulating inhibin responses. Aim II proposes to block betaglycan or disrupt its expression in inhibin-responsive cell types including pituitary gonadotropes. In vitro and in vivo experiments will test the importance of betaglycan as an obligate mediator of inhibin actions. Finally, under Aim III we will search for additional inhibin co-receptors. We and others have evidence for the existence of multiple inhibin binding proteins including probable variants of betaglycan, which we propose to characterize. These studies will improve our understanding of the mechanisms of inhibin action and will help identify targets for the control of fertility and management of reproductive disorders.

激活素和某些 BMP 是 TGF-β 超家族的成员，可调节垂体前叶产生 FSH。它们及其受体在生殖、内分泌和其他系统中也具有多种内分泌、旁分泌和自分泌作用，并在发育和病理生理过程中发挥关键作用。抑制素会对抗激活素的部分但不是全部作用，并且对于生存至关重要，抑制素α无效小鼠的致命表型表明，这些小鼠患有性腺和肾上腺肿瘤以及肝坏死。发挥 在细胞效应中，激活素（β-β二聚体）与其 II 型受体丝氨酸激酶（ActRII 或 ActRIIB）结合，然后募集 I 型受体丝氨酸激酶 (ALK4) 以形成启动下游信号传导的活性复合物。抑制素（α-β 二聚体）与激活素竞争与 ActRII 的结合，但抑制素/ActRII 复合物不会募集 ALK4 或促进信号传导。抑制素是激活素的有效功能拮抗剂，但与激活素相比，抑制素对 ActRII 的亲和力相对较低，这不符合简单的竞争模型。因此，我们寻找了其他成分，在过去的授权期间，我们确定了β聚糖（TGF-β III 型受体）作为一种高亲和力抑制素结合蛋白（共受体），可促进抑制素与 ActRII 结合，从而大大增加抑制素拮抗激活素信号传导的效力。在模型系统中，我们已经证明抑制素可以拮抗对某些 BMP 的反应。在目标 I 下，这些发现将扩展到测试抑制素是否拮抗 BMP 对垂体细胞的影响。我们将继续表征抑制素、β聚糖和 II 型受体 ActRII、ActRIIB 和 BMPRII 之间的结合相互作用。我们将鉴定抑制素结合所需的 β 聚糖残基和区域，并将产生最小化的可溶性 β 聚糖形式，用于生化和结构（项目 II）研究。识别这些蛋白质的关键相互作用表面和区域将有助于设计 调节抑制素反应的策略。 Aim II 提议阻断 β 聚糖或破坏其在抑制素反应细胞类型（包括垂体促性腺激素）中的表达。体外和体内实验将测试β聚糖作为抑制素作用的专性介质的重要性。最后，在目标 III 下，我们将寻找额外的抑制素共受体。我们和其他人有证据表明存在多种抑制素结合蛋白，包括可能的β聚糖变体，我们建议对其进行表征。这些研究将增进我们对抑制素作用机制的理解，并有助于确定控制生育和治疗生殖疾病的目标。