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Regulation of FGF23 by DMP1 in Health and in Chronic Kidney Disease (CKD)

DMP1 在健康和慢性肾脏病 (CKD) 中对 FGF23 的调节

基本信息

批准号：
9314544
负责人：
Aline C Martin
金额：
$ 45.73万
依托单位：
NORTHWESTERN UNIVERSITY AT CHICAGO
依托单位国家：
美国
项目类别：
财政年份：
2015
资助国家：
美国
起止时间：
2015-07-01 至 2020-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9314544
关键词：
Acids Amino Acids Antibodies Area Binding Biological Biological Assay Blood Circulation Bone Marrow Bone Matrix C-terminal Calcinosis Calcitriol Calcium Cardiac Cardiovascular Diseases Cardiovascular system Chronic Kidney Failure Cleaved cell Co-Immunoprecipitations Coupled Data Development Plans Diet Disease Disease Progression Endopeptidases Enzyme-Linked Immunosorbent Assay Enzymes Equilibrium Event Familial hypophosphatemic bone disease Fluorescein-5-isothiocyanate GALNT3 gene Genes Genetic Transcription Goals Health Histology Homeostasis Hormones Human Hypophosphatemia Impairment In Vitro Individual Inherited Interferometry Kidney Knowledge Luciferases Measures Mediating Messenger RNA Metalloendopeptidases Modeling Molecular Morphology Mus Mutation Osteoblasts Osteocytes Peptides Post-Translational Protein Processing Production Proteins Regulation Renal function Reporter Research Research Personnel Rickets Role Scanning Electron Microscopy Site Stromal Cells Syndrome System Testing Therapeutic Toxic effect Transfection Transgenic Mice Transgenic Model Transgenic Organisms Western Blotting Work X Chromosome bone cardiovascular disorder risk career development dentin matrix protein 1 disorder risk experimental study expression vector extracellular fibroblast growth factor 23 glycosylation improved improved outcome in vivo innovation inorganic phosphate mortality mouse model new therapeutic target novel therapeutic intervention overexpression promoter public health relevance therapeutic target tumor wasting

项目摘要

DESCRIPTION (provided by applicant): Chronic kidney disease (CKD) is characterized by an early and progressive increase in osteocyte production of fibroblast growth factor (FGF)-23. Elevated FGF23 levels independently predict cardiovascular events, CKD progression, and mortality, suggesting a need to develop novel therapeutic approaches to reduce FGF23 levels in CKD. Our preliminary data indicate that both increased transcription and reduced cleavage of FGF23 contribute to increased circulating levels of biologically active hormone in CKD, but the mechanisms of these alterations are unknown. To date, most knowledge of FGF23 regulation comes from study of hereditary hypophosphatemic rickets caused by inactivating mutations of the osteocyte proteins, dentin matrix protein (DMP)-1 and phosphate-regulating gene with homology to endopeptidase on the X chromosome (PHEX), that cause elevated FGF23 levels. Like CKD, increased transcription and reduced cleavage of FGF23 drive increased circulating levels in states of DMP1 and PHEX inactivation. Our preliminary data suggest that direct binding of DMP1 to PHEX occurs through the ASARM motif present in the C-terminal fragment of DMP1 (cDMP1) peptide, and that this binding is an essential regulatory mechanism of FGF23 transcription and FGF23 cleavage. Although cDMP1 and PHEX are proven local regulators of FGF23 in bone, no studies have tested the hypothesis that altered PHEX and cDMP1 interactions mediate dysregulated FGF23 transcription and cleavage in CKD. In this proposal, we will apply our expertise in FGF23 regulation in hereditary hypophosphatemia to understand local bone mechanisms regulating FGF23 in CKD. In Aim 1, we will perform interferometry and co-immunoprecipitation experiments to determine if cDMP1 is the active fragment of DMP1 that binds PHEX and inhibits FGF23 transcription. In Aim 2, we will test whether cDMP1 inhibits GALNT3, the enzyme responsible for protecting FGF23 from degradation by glycosylating its cleavage site. In both aims, we will use calcitriol, calcium or phosphate loading as different approaches to induce FGF23 transcription in wild-type (WT) and cDMP1 transgenic (cDMP1Tg) mice and their bone marrow stromal cells (BMSC). We will also use MC3T3-E1 osteoblasts transfected with a luciferase reporter FGF23 promoter or an inducible FGF23 expression vector. In Aim 3, we will use the validated Col4a3ko mouse model of progressive CKD to test our hypothesis that decreased cDMP1 concentrations contribute to increased FGF23 levels in CKD. We will investigate osteocyte organization and morphology using acid etched scanning electron microscopy and FITC-Imaris quantitative modelisation, we will quantify cDMP1 peptides and test whether overexpression of cDMP1 blunts the expected FGF23 increase in Col4a3ko mice, during the course of CKD. These innovative Aims form the basis of the career development plan of a new investigator working in a highly productive FGF23 research team. The results will define an essential role of the PHEX/cDMP1 axis in regulating FGF23, and identify novel therapeutic targets to treat disorders of FGF23 excess, including CKD.