Roles of Gs Alpha and interaction with Wnt signaling in regulation of adipocyte d

Gs Alpha 的作用以及与 Wnt 信号传导在脂肪细胞 d 调节中的相互作用

• 批准号: 8126852
• 负责人: PARTHA S SINHA
• 金额: $ 5.87万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8126852
• 关键词: Ablation; Accounting; Address; Adipocytes; Animal Experimentation; Birth; Bone Density; Bone Diseases; Bone Marrow; Cells; Clinical; Colony-Forming Units Assay; Cyclic AMP; Disease; Equilibrium; Exhibits; G Protein-Coupled Receptor Signaling; GTP-Binding Protein alpha Subunits, Gs; Gene Expression; Gene Targeting; Goals; Green Fluorescent Proteins; Heterotrimeric G Protein Subunit; Hormones; In Vitro; Laboratories; Laboratory Study; Lithium; Mediating; Membrane; Messenger RNA; Metabolic Diseases; Modeling; Molecular; Multiple Fractures; Mus; Mutant Strains Mice; Obesity; Osteoblasts; Osteocytes; Osteoporosis; Parathyroid Hormone Receptor; Parathyroid gland; Receptor Signaling; Regulation; Relative (related person); Reporter; Reporter Genes; Reporting; Role; Signal Transduction; Stem cells; Stromal Cells; Testing; Tomatoes; adipocyte differentiation; base; bone cell; bone mass; dimer; improved; in utero; in vivo; inhibitor/antagonist; osteoblast differentiation; osteoprogenitor cell; progenitor; research study; skeletal disorder

DESCRIPTION (provided by applicant): Adipocytes and osteoblasts may share a common precursor residing in the bone marrow. This is suggested by clinical observations and animal research models which demonstrate an inverse relationship between bone marrow adiposity and bone density. Elucidation of the mechanisms governing how bone marrow stromal cells differentiate into adipocytes and osteoblasts may carry implications for metabolic diseases such as obesity and of bone diseases such as osteoporosis. Our studies focus on the potential role in this mechanism of Gsa, a heterotrimeric G protein subunit that mediates cyclic AMP-dependent signaling of G protein-coupled receptors including the parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor (PPR). PPR signaling is believed to promote osteoblast differentiation and may also suppress adipocyte differentiation. These actions may be mediated in part by canonical Wnt signaling. Studies from this laboratory revealed that mice with targeted deletion of Gsa early in the osteoblast lineage (Osterix-Cre:Gsa(fl/fl)) exhibit osteoporosis and multiple fractures at birth along with increased bone marrow adiposity. This laboratory previously reported that Osterix-Cre:Gsa(fl/fl) mice have increased expression of sclerostin, an inhibitor of canonical Wnt signaling secreted by osteocytes, and decreased gene expression of Wnt target genes. Based on these observations, we hypothesized that Gsa expressed in cells of the early osteoblast lineage has a role in regulation of osteoblast and adipocyte differentiation, and that this role was mediated in part by canonical Wnt signaling. Preliminary studies using in vitro colony forming unit assays suggested that targeted deletion of Gsa early in the osteoblast lineage leads to fewer numbers of total progenitor cells and osteoprogenitor cells, but does not change the number of adipocyte progenitors. The question remains, however, whether the increased adipogenic potential of cells derived from Osterix-Cre:Gsa fl/fl mice is accounted for by increased adipocyte progenitor number or conversion of Gsa null osteoblasts into adipocytes. The experiments of Specific Aim I address this question by using the the double fluorescent reporter gene membrane-targeted tandem dimer tomato/green fluorescent protein to identify adipocytes that expressed Osterix:Cre and thus presumably were originally of the osteoblast lineage. The experiments of Specific Aim II address the potential role of Wnt signaling in how Gsa signaling in early osteoblasts regulates adipocyte and osteoblast differentiation. Firstly, these experiments will study whether there is decreased Wnt activity in Osterix-Cre:Gsa mice. Secondly, we will study whether Gsa signaling in early osteoblasts interact Wnt signaling upstream of b-catenin stabilization. This question will address by testing the effects of in utero lithium exposure on Osterix-Cre:Gsa fl/fl mice upon bone mass, bone marrow adiposity, and relative numbers of adipocyte progenitors and osteoprogenitors. PUBLIC HEALTH RELEVANCE: This study focuses on mechanisms underlying how fat cells and bone cells develop from the bone marrow. This may help improve understanding and treatment of diseases such as obesity and osteoporosis.

描述（由申请人提供）：脂肪细胞和成骨细胞可能在骨髓中有共同的前体。临床观察和动物研究模型表明，骨髓脂肪与骨密度呈反比关系。阐明骨髓基质细胞如何分化为脂肪细胞和成骨细胞的机制可能对代谢疾病（如肥胖）和骨病（如骨质疏松症）具有启示意义。Gsa是一种异三聚体G蛋白亚基，介导包括甲状旁腺激素(PTH)/PTH相关肽（PTHrP）受体（PPR）在内的G蛋白偶联受体的环amp依赖性信号传导，我们的研究重点是Gsa在该机制中的潜在作用。PPR信号被认为促进成骨细胞分化，也可能抑制脂肪细胞分化。这些作用可能部分由典型Wnt信号介导。该实验室的研究表明，在成骨细胞谱系早期靶向缺失Gsa的小鼠（Osterix-Cre:Gsa(fl/fl)）在出生时表现出骨质疏松症和多发性骨折，同时骨髓脂肪增加。本实验室此前报道，Osterix-Cre:Gsa（fl/fl）小鼠的骨细胞分泌的典型Wnt信号抑制剂sclerostin的表达增加，Wnt靶基因的基因表达降低。基于这些观察，我们假设在早期成骨细胞谱系中表达的Gsa在成骨细胞和脂肪细胞分化的调节中起作用，并且这种作用部分是由典型的Wnt信号通路介导的。使用体外集落形成单位测定的初步研究表明，在成骨细胞谱系早期靶向删除Gsa导致总祖细胞和骨祖细胞数量减少，但不改变脂肪细胞祖细胞的数量。然而，问题仍然是，来自Osterix-Cre:Gsa fl/fl小鼠的细胞成脂潜能的增加是否与脂肪细胞祖细胞数量的增加或Gsa无成骨细胞向脂肪细胞的转化有关。Specific Aim I的实验解决了这个问题，使用双荧光报告基因膜靶向串联二聚体番茄/绿色荧光蛋白来鉴定表达Osterix:Cre的脂肪细胞，因此可能最初属于成骨细胞谱系。特异性Aim II的实验探讨了Wnt信号在早期成骨细胞Gsa信号调节脂肪细胞和成骨细胞分化中的潜在作用。首先，本实验将研究Osterix-Cre:Gsa小鼠Wnt活性是否降低。其次，我们将研究早期成骨细胞中的Gsa信号是否与b-连环蛋白稳定上游的Wnt信号相互作用。这个问题将通过测试子宫内暴露于Osterix-Cre:Gsa fl/fl小鼠对骨量、骨髓脂肪以及脂肪祖细胞和骨祖细胞相对数量的影响来解决。