THE PHYSIOLOGY OF IGFBP DEGRADING PROTEINASES IN BONE

IGFBP 降解骨中蛋白酶的生理学

• 批准号: 6866079
• 负责人: John L Fowlkes
• 金额: $ 6.53万
• 依托单位: ARKANSAS CHILDREN'S HOSPITAL RES INST
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-06-15 至 2005-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6866079
• 关键词: SDS polyacrylamide gel electrophoresis; binding proteins; bone development; bone morphogenetic proteins; enzyme activity; enzyme inhibitors; genetic library; genetically modified animals; high performance liquid chromatography; insulinlike growth factor; laboratory mouse; metalloendopeptidases; molecular cloning; northern blottings; nucleic acid sequence; osteoblasts; polymerase chain reaction; protein degradation; protein sequence; protein structure function; receptor coupling; receptor expression; western blottings

Bone is a dynamic organ which undergoes a balanced, ongoing reorganization requiring both bone formation (anabolism) and bone resorption (catabolism). The interplay between these two processes is referred to as coupling. In bone, insulin-like growth factors (IGF-I and IGF-II) are important mitogens in bone formation. These growth factors' actions are, however, modulated by high affinity IGF-binding proteins (IGFBP 1-6). Recent data shows that when bound to soluble IGFBPs, IGFs are unable to interact with their cell surface receptors. In contrast, when IGFBPs are degraded by proteinases or when they are complexed with matrix molecules, their affinity for IGFs is lowered, making IGFs available to interact with cell surface type I IGF receptors. We hypothesize that the interplay between IGFBP-degrading proteinases and IGF/IGFBP complexes plays an integral role in the process of bone coupling. For instance, many of the proteinases involved in bone resorption, such as matrix metalloproteinases (MMPs), also degrade IGFBPs. Degradation of IGFBPs, in turn, results in the release IGFs to function as anabolic agents in bone formation. The overall objective of this proposal is to clarify which proteinases are involved in the degradation of two important bone-derived IGFBPs, IGFBP-4 and IGFBP-5, and to determine their overall contribution to the anabolic actions of IGFs in bone cells. The proposed studies are designed to a) understand the roles of MMPs on IGFBP-5 degradation and how degradation of this IGFBP affects IGF bioavailability in osteoblasts; b) clarify the role of the novel L56 proteinase in IGFBP-4 degradation and define the factors which regulate its production and activity in bone; and c) utilize new methodologies to identify and clone novel IGFBP-degrading proteinases in human bone. A better understanding of the proteinases involved in IGFBP degradation and their physiologic role in IGF action will allow for development of therapeutic interventions to enhance bone formation by increasing IGF biovailability or by decreasing bone resorption in a variety of bone disorders such as osteoporosis and metabolic bone diseases.

骨骼是一种动态器官，经过平衡，持续的重组，需要骨形成（合成代谢）和骨吸收（分解代谢）。 这两个过程之间的相互作用称为耦合。 在骨骼中，胰岛素样生长因子（IGF-I和IGF-II）在骨形成中是重要的有丝分裂剂。 但是，这些生长因子的作用是由高亲和力IGF结合蛋白（IGFBP 1-6）调节的。 最近的数据表明，当与可溶性IGFBP绑定时，IGF无法与细胞表面受体相互作用。 相反，当IGFBP被蛋白酶降解或与基质分子复合时，它们对IGF的亲和力降低，从而使IGF可用于与I型IGF受体相互作用。 我们假设IGFBP降解蛋白酶与IGF/IGFBP配合物之间的相互作用在骨耦合过程中起着不可或缺的作用。 例如，许多参与骨吸收的蛋白酶，例如基质金属蛋白酶（MMP），也降解IGFBP。反过来，IGFBP的降解导致释放IGF充当骨形成的合成代谢剂。 该提案的总体目的是阐明哪些蛋白酶参与了两个重要的骨源性IGFBPS，即IGFBP-4和IGFBP-5，并确定它们对IGF在骨细胞中的合成代谢作用的总体贡献。 拟议的研究旨在a）了解MMP在IGFBP-5降解中的作用，以及该IGFBP的降解如何影响成骨细胞中的IGF生物利用度； b）阐明了新型L56蛋白酶在IGFBP-4降解中的作用，并定义了调节其骨骼产生和活性的因素； c）利用新方法来识别和克隆人骨中的新型IGFBP降解蛋白酶。 更好地了解IGFBP降解及其在IGF作用中的生理作用的蛋白酶将通过增加IGF生物可消除性或减少多种骨骼疾病（如骨质疏松症和代谢骨疾病）中的骨骼吸收来增强骨形成，从而增强治疗性干预措施。