IGF RECEPTOR AND BINDING PROTEIN PATTERNS IN BONE

骨骼组织的动态平衡由骨吸收和骨来平衡 队形。这些过程的生理整合称为 重塑，而决定平衡的机制被称为 耦合。胰岛素样生长因子I(IGF-I)似乎是一种偶联 因为它是由骨细胞产生的或在吸收过程中释放的， 并增强前体细胞复制和新骨基质的产生。 IGF-I的合成受到系统和局部产生的因素的调节，并且 骨细胞也会产生大量的IGF-II。高额的 骨骼中的内源性IGF预测有必要通过以下方式调节其行为 除了调节它们的合成之外的机制。在这方面，骨细胞 产生几种胰岛素样生长因子结合蛋白(IGFBPs)，并表达IGFBP 也受到激素和局部因素的控制。各种IGFBP可以 具有独立或重叠的影响，通过这些影响使它们本地化、隔离、 抑制或增强IGF活性，可能是通过影响相互作用 IGFS和IGF受体之间的相互作用。此外，IGF受体的变化 数量和亲和力，以及类型1的相对量(高亲和力IGF- I；信号转导)和2型(高亲和力IGF-II；甘露糖-6- 磷酸转移酶)受体可能控制IGF的作用。这些研究 这里将研究IGFBPs的合成和本地化 由原代细胞培养产生，代表分化较少和 胎鼠分化更多(成骨细胞丰富；Ob)群体 顶骨组织中胰岛素样生长因子1型和2型受体的表达 这些文化。这些研究将特别集中在诱导剂 CAMP(从而激活蛋白激酶A；PKA)，并增加 蛋白激酶C(PKC)活性。这些代理包括三种形式的 前列腺素、福司可林和佛波酯，它们独立或 同时增加cAMP和PKC依赖的细胞事件。这两个 不同类型的药物对IGF-I和IGFBP有不同的影响 在Ob培养中表达和IGF受体结合，并产生不同的 低分化培养和Ob培养中的代谢差异。这些 研究将系统地检查IGFBPs在以下水平的表达 MRNA(Northern分析)和蛋白质(Western配体和抗体) 探索)在差异较小的Ob文化中对两者的回应 代理的类别。1型和2型胰岛素样生长因子受体的分布 培养将在mRNA水平上进行评估(通过核糖核酸酶保护 分析)和蛋白质(通过Scatchard分析，聚丙烯酰胺凝胶 电泳法和磷酸化状态)来区分特定的 每一处都有变化。许多促钙激素还是当地生产的 增加吸收的因素激活cAMP或PKC依赖事件， 这些因素中有几个是通过细胞以外的其他方式间接作用的 骨骼中的破骨细胞。因此，仔细描述IGFBP和 IGF受体在非破骨细胞性骨细胞中的表达 激活cAMP或PKC的代理，对于了解 胰岛素样生长因子活性调控的生化和分子机制 骨骼组织。骨质疏松等衰弱的骨病确切地说是 痛苦给个人和社会带来沉重负担，限制了 机动性和高昂的医疗费用。虽然该病的病因 骨质疏松症各有不同，基本特征是骨量丢失和 骨折发生率增加。从工作中收集的信息 在这里提出的建议可以帮助设计适当的干预方法 在这种代谢和其他代谢中促进骨形成或最大限度减少骨丢失 骨病。

Skeletal tissue homeostasis is balanced by bone resorption and bone formation. The physiological integration of these processes is called remodeling, whereas the mechanisms that determine balance are called coupling. Insulin-like growth factor I (IGF-I) appears to be one coupling factor since it is produced by bone cells or released during resorption, and enhances precursor cell replication and new bone matrix production. IGF-I synthesis is regulated by systemic and locally produced factors, and bone cells also produce abundant levels of IGF-II. The high amount of endogenous IGFs in bone predicts the need to regulate their actions by mechanisms beyond modulating their synthesis. In this regard, bone cells produce several of the IGF binding proteins (IGFBPs), and IGFBP expression is also under hormone and local factor control. The various IGFBPs may have independent or overlapping effects by which they localize, sequester, inhibit or potentiate IGF activity, probably by influencing interactions between IGFs and IGF receptors. Furthermore, changes in IGF receptor number and affinity, and the relative amount of type 1 (high affinity IGF- I; signal transducing) and type 2 (high affinity IGF-II; mannose-6- phosphate transferase) receptors may control IGF actions. The studies proposed here will examine the synthesis and localization of IGFBPs produced by primary cell cultures that represent less differentiated and more differentiated (osteoblast-enriched; Ob) populations from fetal rat parietal bone, and the expression of type 1 and type 2 IGF receptors in these cultures. The studies will focus specifically on agents that induce cAMP (and thereby activate protein kinase A; PKA), and that increase protein kinase C (PKC) activity. These agents include three forms of prostaglandin, forskolin, and phorbol ester, which independently or simultaneously increase cAMP and PKC dependent cellular events. These two classes of agents potently and differentially influence IGF-I and IGFBP expression, and IGF receptor binding in Ob cultures, and produce distinct metabolic differences in less differentiated and Ob cultures. These studies will systematically examine expression of IGFBPs at the levels of mRNA (by Northern analysis) and protein (by Western ligand and antibody probing) in less differentiated and Ob cultures in response to both classes of agents. Type 1 and type 2 IGF receptor profiles in each culture will be assessed at the levels of mRNA (by RNase protection analysis) and protein (by Scatchard analysis, polyacrylamide gel electrophoresis, and phosphorylation state) to distinguish specific alterations in each. Many calciotropic hormones or locally produced factors that increase resorption activate cAMP or PKC dependent events, and several of these factors act indirectly by way of cells other than osteoclasts in bone. Therefore, a careful characterization of IGFBP and IGF receptor expression in non-osteoclastic bone cells, with attention to agents that activate cAMP or PKC, is critical in order to understand the biochemical and molecular mechanisms that regulate IGF activity in skeletal tissue. Debilitating bone diseases such as osteoporosis exact a heavy burden on individuals and on society due to pain, limitations in mobility, and high cost medical care. Although the etiology of osteoporosis varies, the underlying feature is loss of bone mass and increased fracture incidence. The information collected from the work proposed here could help to design appropriate intervention methods to enhance bone formation or minimize bone loss in this and other metabolic bone diseases.