SECOND MESSENGERS IN PARATHYROID HORMONE ACTION

描述：（直接取自应用程序）甲状旁腺激素（PTH）对骨骼的作用是多种多样的，可能导致骨骼质量的净增加或减少，这取决于循环激素的时间和浓度概况。间歇性（每日一次）甲状旁腺激素显示出治疗骨质疏松症的希望，但需要更多的了解甲状旁腺激素在骨中的细胞作用，以提高这种方法的疗效。PTH激活成骨细胞（OBs）和骨髓基质细胞（MSCs）表达的PTH/PTHrP受体（PTHRs），但不激活成熟破骨细胞（ocl）表达的PTH/PTHrP受体（PTHRs），尽管它可能对OBs和ocl的早期祖细胞都有直接影响。PTHR激活多种平行效应——腺苷酸环化酶（AC）、磷脂酶c （PLC）和胞质游离钙瞬态——调节骨靶细胞的增殖、分化和其他功能，但PTHR信号或信号模式与靶细胞群体中不同的细胞反应程序之间的联系尚不清楚。先前在体外处理这些问题的努力受到了限制，因为无法获得均匀的、非转化的正常PTH靶细胞群体和调节其PTHR信号的特定技术。本项目的主要目标是利用新的、有条件转化的克隆OB、MSC和OCL祖细胞系，在这些细胞系中PTHR的表达和信号可以被特异性修饰，以确定PTHR和单个PTHR信号在激素的关键细胞效应中的作用。通过基因消融消除内源性PTHR，并用正常或信号选择性突变的PTHR代替它们，将创建一组其他类型相同的克隆骨细胞系，用于评估细胞对特定PTHR信号的反应。与新的信号选择性PTH类似物一起，可以指导正常PTHR发出异常信号，这些细胞系统将能够直接在体外检测PTHR及其信使信号在控制OB和OCL分化中的作用，包括脉动性和连续PTH暴露对体内骨骼的可能差异影响。进入PTH -null细胞也将允许清晰地检测可能由这些细胞正常表达的其他种类的PTH受体的作用。从这些研究中得出的对甲状旁腺激素作用的新认识将对进一步开发具有骨骼活性的甲状旁腺激素类似物具有不可估量的价值。

Description:(Taken directly from the application) The actions of parathyroid hormone (PTH) on bone are diverse and may cause a net gain or loss of skeletal mass, depending upon the temporal and concentration profiles of the circulating hormone. Intermittent (once daily) PTH shows promise for therapy of osteoporosis, but more knowledge of the cellular actions of PTH in bone is needed to enhance the efficacy of this approach. PTH activates PTH/PTHrP receptors (PTHRs) expressed by osteoblasts (OBs) and marrow stromal cells (MSCs) but not by mature osteoclasts (OCLs), although it may exert direct effects on early progenitors of both OBs and OCLs. PTHRs activate multiple parallel effectors-adenylyl cyclase (AC), phospholipase-C (PLC) and cytosolic free calcium transients-that modulate proliferation, differentiation and other functions in target cells of bone, but the links between specific PTHR signals, or patterns of signals, and distinctive programs of cellular responses in each population of target cells are poorly understood. Previous efforts to approach these issues in vitro were constrained by unavailability of homogeneous, nontransformed populations of normal PTH target cells and of specific techniques for modulating their PTHR signaling. The main goal of this project is to utilize novel, conditionally transformed, clonal OB, MSC and OCL progenitor cell lines, in which PTHR expression and signaling can be specifically modified, to determine the roles of the PTHR and of individual PTHR signals in the key cellular effects of the hormone. By eliminating endogenous PTHRs through gene ablation and replacing them with normal or signal-selective mutant PTHRs, a panel of otherwise-identical clonal bone cell lines of each type will be created with which to assess the cellular responses to specific PTHR signals. Together with new signal-selective PTH analogs that can instruct normal PTHRs to signal aberrantly, these cell systems will enable direct in vitro assays of the role of the PTHR and its messenger signals in controlling OB and OCL differentiation, including the possible differential impact of pulsatile and continuous PTH exposures that have opposite effects on bone in vivo. Access to PTHR-null cells also will allow unobscured detection of the effects of other species of PTH receptors that may be expressed normally by these cells. The new understanding of PTH action that should flow from these studies will be invaluable for further development of skeletally active PTH analogs.