1,25-(OH)2D3 down-regulates expression of Phex, a marker of the mature osteoblast
1,25-(OH)2D3 down-regulates expression of Phex, a marker of the mature osteoblast
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DOI：
10.1210/en.140.3.1192
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发表时间：
1999-03-01
期刊：
影响因子：
4.8
通讯作者：
Desbarats, M
中科院分区：
文献类型：
--
作者：
Ecarot, B;Desbarats, M
PHEX/PHEX基因的突变是人类和小鼠X连锁低磷血症的原因，该基因编码一种与中性内肽酶同源的蛋白质。本研究检测了成骨细胞中PHEX信使RNA和蛋白的表达以及1，25-(OH)(2)D-3对其的调节作用。用密度计量学方法对Northern blotts上的PHEX mRNA水平进行了定量，并与GAPDHmRNA水平进行了比较。免疫沉淀法检测免疫反应阳性的PHEX蛋白水平，使用针对小鼠PHEX羧基末端肽的多克隆兔抗血清。在原代成骨细胞培养中，β-甘油磷酸诱导的基质矿化与PHEX mRNA和蛋白的显著增加有关。在增殖的成骨前细胞MC3T3-E1中，PHEX的mRNA和蛋白水平很低或检测不到，并随着基质矿化的启动而显著增加。然而，在没有β-甘油磷酸的非矿化培养中，PHEX的表达模式与之相似，表明在MC3T3-E1细胞中PHEX表达的诱导与细胞分化有关，而不是与基质矿化有关。1，25-(OH)(2)D-3以时间和剂量依赖的方式抑制矿物质沉积，下调PHEX基因和蛋白的表达。这些结果表明，PHEX是成骨细胞完全分化的标志，其表达在β-甘油磷酸诱导的原代成骨细胞矿化过程中被刺激，并被基质矿化抑制剂1，25-(OH)(2)D-3下调。这些发现进一步支持了PHEX在骨矿化中的重要作用。
Mutations in the PHEX/Phex gene, which encodes for a protein with homology to neutral endopeptidases, are responsible for human and murine X-linked hypophosphatemia. The present study examined Phex messenger RNA (mRNA) and protein expression in cultured osteoblasts and its regulation by 1,25-(OH)(2)D-3. Phex mRNA levels were quantitated on Northern blots by densitometric analysis relatively to GAPDH mRNA levels. Immunoreactive Phex protein levels were evaluated by immunoprecipitation using a polyclonal rabbit antiserum raised against a mouse Phex carboxy-terminal peptide.beta-Glycerophosphate-induced matrix mineralization in primary osteoblast cultures was associated with significant increases in Phex mRNA and protein. Phex mRNA and protein levels were low or undetectable in proliferating preosteoblastic MC3T3-E1 cells and dramatically increased concomitantly with initiation of matrix mineralization. The pattern of Phex expression, however, was similar in nonmineralizing cultures grown in the absence of beta-glycerophosphate, indicating that the induction of Phex expression in MC3T3-E1 cells was related to cell differentiation rather than matrix mineralization. 1,25-(OH)(2)D-3 inhibited mineral deposition and down-regulated Phex mRNA and protein expression in a time- and dose-dependent manner.These results indicate that Phex is a marker of the fully differentiated osteoblast and that its expression is stimulated during beta-glycerophosphate-induced mineralization in primary osteoblast cultures and down-regulated by 1,25-(OH)(2)D-3, an inhibitor of matrix mineralization. These findings add support for Phex having an important role in bone mineralization.