Determination of the mechanisms by which IGFBP-2 stimulates bone remodeling

确定 IGFBP-2 刺激骨重塑的机制

• 批准号: 8190538
• 负责人: DAVID Robert CLEMMONS
• 金额: $ 47.26万
• 依托单位: MAINEHEALTH
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8190538
• 关键词: 1-Phosphatidylinositol 3-Kinase; Address; Adult; Affect; Age; Amino Acids; Binding; Biological Assay; Bone Growth; Bone Marrow; Bone remodeling; Calvaria; Carrier Proteins; Cell Differentiation process; Cell Proliferation; Cell Surface Proteins; Cell Surface Receptors; Cells; Co-Immunoprecipitations; Complex; DEFB1 gene; Defect; Development; Dual-Energy X-Ray Absorptiometry; Family; Future; Gene Expression; Genetically Engineered Mouse; Goals; Growth; Hematopoietic; Hematopoietic stem cells; Heparin Binding; In Vitro; Inbreeding; Insulin-Like Growth Factor Binding Protein 3; Insulin-Like Growth Factor I; Insulin-Like Growth Factor II; Insulin-Like Growth Factor Receptor; Insulin-Like Growth-Factor-Binding Proteins; Interdisciplinary Study; Laboratories; Lead; Length; Ligands; Magnetic Resonance Imaging; Maintenance; Marrow; Mediating; Membrane; Mesenchymal; Metabolic Bone Diseases; Metatarsal bone structure; Molecular; Molecular Profiling; Mus; Myelogenous; Nuclear; Osteoblasts; Osteoclasts; Osteogenesis; PTEN gene; Pathway interactions; Peptide Hydrolases; Peptides; Phenotype; Phosphorylation; Physiologic calcification; Production; Proto-Oncogene Proteins c-akt; Public Health; Relative (related person); Role; Serine; Signal Pathway; Signal Transduction; Skeleton; Somatomedins; Staging; Stromal Cells; Sum; System; Testing; Transcript; Transplantation; Tyrosine Phosphorylation; Work; bone; bone cell; bone mass; bone turnover; congenic; human IGFBP2 protein; in vivo; indexing; insight; lipid biosynthesis; mineralization; mutant; novel; osteoblast differentiation; osteoclastogenesis; osteogenic; pleiotrophin; receptor; reconstitution; research study; skeletal; small molecule; substantia spongiosa

DESCRIPTION (provided by applicant): The long term goal of this proposal is to define the role of insulin like growth factor binding protein-2 (IGFBP-2) in skeletal acquisition and maintenance, and to determine the mechanisms whereby this molecule acts synergistically with IGF-I to regulate bone remodeling. The IGF regulatory system in bone includes a family of highly conserved IGF binding proteins (IGFBPs), proteases, receptors and the IGFs. IGFBP-2 is highly expressed in osteoblasts, and it stimulates mesenchymal stromal cell (MSC) proliferation. Global Igfbp2-/- mice have low bone turnover, impaired osteoblast and osteoclast differentiation, and accelerated marrow adipogenesis. To determine the mechanism of action of IGFBP-2 independent of IGF-I, we synthesized a short 13 amino acid peptide that does not bind IGFs but contains a unique heparin binding domain within IGFBP-2 (i.e. HBD1), and showed that HBD1 stimulated OB differentiation as did intact IGFBP-2. Daily administration of a pegylated form of the HBD1 peptide to Igfbp2 -/- mice for 3 weeks rescued their low trabecular bone mass, increased OB number, and enhanced hematopoietic progenitor cells. Osteoblasts from Igfbp2-/- mice have increased PTEN (phosphatase and tensin homolog) transcripts which can be suppressed by addition of exogenous IGFBP-2, IGF-I or HBD. Phosphorylation of AKT in MSCs from Igfbp2-/- mice was greatest when IGF-I + IGFBP-2 were added. Taken together, we hypothesize that IGFBP-2, which is induced by IGF-I, stimulates MSCs and OBs through HBD1. Furthermore we postulate that IGF-I and IGFBP-2 normally act in a complementary manner to promote bone remodeling by acting synergistically through distinct cell surface receptors. The two specific aims proposed are: 1) to determine IGFBP-2 actions on bone remodeling and its role in lineage allocation of MSCs, HSCs, and osteoclast precursors. 2) To delineate the molecular mechanism(s) of IGFBP-2 actions on bone cells, and determine if HBD1 is sufficient to mediate these effects through the pleiotrophin receptor. Using the HBD1 peptide we will study how IGFBP-2 affects the intracellular signaling pathways that promote cell proliferation. These interdisciplinary studies will lead to a clearer understanding of the function of IGFBP-2 in the adult skeleton. PUBLIC HEALTH RELEVANCE: This proposal has significant public health implications since it will help delineate the role of the IGF regulatory system in bone. Importantly, studies of the heparin binding domain will determine whether this small molecule can be used for the treatment of metabolic bone disorders.

描述（由申请人提供）：该提案的长期目标是确定胰岛素样生长因子结合蛋白 2 (IGFBP-2) 在骨骼获得和维持中的作用，并确定该分子与 IGF-I 协同作用以调节骨重塑的机制。骨骼中的 IGF 调节系统包括高度保守的 IGF 结合蛋白 (IGFBP)、蛋白酶、受体和 IGF 家族。 IGFBP-2 在成骨细胞中高表达，并刺激间充质基质细胞 (MSC) 增殖。 Global Igfbp2-/- 小鼠骨转换率低、成骨细胞和破骨细胞分化受损、骨髓脂肪生成加速。为了确定 IGFBP-2 独立于 IGF-I 的作用机制，我们合成了一种短的 13 个氨基酸肽，该肽不结合 IGF，但在 IGFBP-2 内包含独特的肝素结合结构域（即 HBD1），并表明 HBD1 与完整的 IGFBP-2 一样刺激 OB 分化。每日向 Igfbp2 -/- 小鼠施用聚乙二醇化形式的 HBD1 肽 3 周，可挽救其低骨小梁质量、增加 OB 数量并增强造血祖细胞。 Igfbp2-/- 小鼠的成骨细胞具有增加的 PTEN（磷酸酶和张力蛋白同源物）转录物，可通过添加外源 IGFBP-2、IGF-I 或 HBD 来抑制这种转录物。当添加 IGF-I + IGFBP-2 时，来自 Igfbp2-/- 小鼠的 MSC 中 AKT 的磷酸化程度最高。综上所述，我们假设 IGF-I 诱导的 IGFBP-2 通过 HBD1 刺激 MSC 和 OB。此外，我们假设IGF-I和IGFBP-2通常以互补的方式发挥作用，通过不同的细胞表面受体协同作用来促进骨重塑。提出的两个具体目标是：1) 确定 IGFBP-2 对骨重塑的作用及其在 MSC、HSC 和破骨细胞前体谱系分配中的作用。 2) 描述 IGFBP-2 对骨细胞作用的分子机制，并确定 HBD1 是否足以通过多效蛋白受体介导这些作用。使用 HBD1 肽，我们将研究 IGFBP-2 如何影响促进细胞增殖的细胞内信号通路。 这些跨学科研究将使人们更清楚地了解 IGFBP-2 在成人骨骼中的功能。 公共卫生相关性：该提案具有重大的公共卫生影响，因为它将有助于描述 IGF 调节系统在骨骼中的作用。重要的是，对肝素结合域的研究将确定这种小分子是否可用于治疗代谢性骨疾病。