THE PHYSIOLOGY OF IGFBP DEGRADING PROTEINASES IN BONE

IGFBP 降解骨中蛋白酶的生理学

• 批准号: 6177453
• 负责人: John L Fowlkes
• 金额: $ 22.34万
• 依托单位: UNIVERSITY OF KENTUCKY
• 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 2003-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6177453
• 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.

骨骼是一个动态器官，它经历平衡、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）是骨形成中重要的有丝分裂原。 然而，这些生长因子的作用受到高亲和力 IGF 结合蛋白 (IGFBP 1-6) 的调节。 最近的数据表明，当与可溶性 IGFBP 结合时，IGF 无法与其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 的亲和力就会降低，从而使 IGF 能够与细胞表面 I 型 IGF 受体相互作用。 我们假设 IGFBP 降解蛋白酶和 IGF/IGFBP 复合物之间的相互作用在骨偶联过程中发挥着不可或缺的作用。 例如，许多参与骨吸收的蛋白酶，例如基质金属蛋白酶 (MMP)，也会降解 IGFBP。 IGFBP 的降解反过来导致 IGF 的释放，在骨形成中充当合成代谢剂。 该提案的总体目标是阐明哪些蛋白酶参与两种重要的骨源性 IGFBP（IGFBP-4 和 IGFBP-5）的降解，并确定它们对骨细胞中 IGF 合成代谢作用的总体贡献。 拟议的研究旨在 a) 了解 MMP 对 IGFBP-5 降解的作用以及 IGFBP 的降解如何影响成骨细胞中的 IGF 生物利用度； b) 阐明新型 L56 蛋白酶在 IGFBP-4 降解中的作用，并确定调节其在骨中产生和活性的因素； c) 利用新方法来鉴定和克隆人骨中新型 IGFBP 降解蛋白酶。 更好地了解参与 IGFBP 降解的蛋白酶及其在 IGF 作用中的生理作用，将有助于开发治疗干预措施，通过增加 IGF 生物利用度或减少各种骨疾病（如骨质疏松症和代谢性骨疾病）的骨吸收来增强骨形成。