NEUROENDOCRINE PEPTIDES/ RECEPTORS REGULATE GONADOTROPHS

激活素和促性腺激素是TGF β家族的生长和分化的成员，其通过其对FSH产生的相互作用而被发现。这些多效性蛋白质在正常和肿瘤性生殖组织和其它组织中发挥广泛的内分泌、旁分泌和自分泌作用。激活素与其特异性II型受体丝氨酸激酶激酶（RSK）的结合导致其同源I型RSK（激活素样激酶-4）的募集和转磷酸化以及下游介体（途径特异性Smads）的后续磷酸化。在目标I下，我们将研究激活素信号传导组分之间相互作用的性质。基于项目III对II型激活素受体配体结合结构域的阐明，我们正在哺乳动物细胞中表达一系列突变体受体，并分析它们对激活素、Escherichin和I型受体（ALK 4）的亲和力。这些努力与Choe（项目III）和Fischer（项目IV）高度互补，Choe正在解决ActRII/激活素/ALK 4复合物的结构，Fischer正在突变激活素本身。第二个目标涉及研究用于限制激活素本身的生物学效应的机制。我们已经观察到细胞脱敏的转录响应激活素，并将探讨机制，包括可能性，这是由抑制性Smad，Smad 7介导的。我们将继续探索的作用模式，这将包括一个持续的努力，克隆一个特异性结合组件。如果我们成功了，一系列的生化和细胞实验将确保确定这种蛋白质的重要性。如果有必要，我们将产生和分析缺乏Escherichin受体的小鼠。根据目标III，我们将继续探讨垂体内的旁分泌和自分泌机制，研究一些细胞因子效应可能通过增加卵泡抑素的产生来介导的有趣的可能性。Smad 7在垂体和促性腺激素中的作用和调节将通过多种方法进行探索，包括产生Smad 7无效小鼠，其中，Smad 7在促性腺激素中被条件性敲除。这种垂体内调节网络提供了一种整合中枢和外周输入的机制，并可能对特定生理环境下FSH和LH的差异产生至关重要。针对细胞外和细胞内激活素信号系统的药物和其他方法可能被证明对人类生育和生殖疾病的管理有用。

Activins and inhibins are members of the TGFbeta family of growth and differentiation that were discovered by virtue of their reciprocal effects on the production of FSH. These pleiotropic proteins play a wide variety of endocrine, paracrine and autocrine roles within normal and neoplastic reproductive and other tissues. The binding of activin to its specific type II receptor serine kinase kinase (RSK) leads to the recruitment and trans- phosphorylation of its cognate type I RSK (Activin Like Kinase-4) and the subsequent phosphorylation of downstream mediators, the pathway- specific Smads. Under Aim I, we will examine the nature of the interactions between the components of activin signaling. Based on the elucidation of the structure of the ligand binding domain of the type II activin receptor by Project III, we are expressing a series of mutant receptors in mammalian cells and analyzing their affinities for activin, inhibin and the type I receptor (ALK4). These efforts are highly complementary to Choe (Project III), who is working to solve the structure of the ActRII/activin/ALK4 complex and to Fischer (Project IV) who is mutating activin itself.. The second Aim involves the study of mechanisms that serve to limit the biological effects of activin itself. We have observed cellular desensitization of the transcriptional response to activin and will explore mechanisms, including the possibility that this is mediated by the inhibitory Smad, Smad7. We will continue to explore the mode of action of inhibin; this will include a continued effort to clone an inhibin specific binding component. If we are successful, a series of biochemical and cellular experiments will ensure to determine the importance of this protein. If warranted, we will generate and analyze mice deficient in the inhibin receptor. Under Aim III we will continue to explore paracrine and autocrine mechanisms within the pituitary, examining the interesting possibility that some cytokine effects may be mediated through increased production of follistatin. The roles and regulation of Smad7 in the pituitary and gonadotropes, will be explored by a variety of approaches, including the generation of Smad 7 null mice, in which, Smad7 is conditionally knocked out in gonadotropes. This intra-pituitary modulatory network provides a mechanism for the integration of central and peripheral inputs and may be critical for the differential production of FSH and LH under defined physiological circumstances. Drugs and other approaches targeting components of the extracellular and intracellular activin signaling system may prove to be useful for the management of human fertility and reproductive disorders.