Cloning and sequencing of human PEX from a bone cDNA library: Evidence for its developmental stage-specific regulation in osteoblasts
Cloning and sequencing of human PEX from a bone cDNA library: Evidence for its developmental stage-specific regulation in osteoblasts
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DOI：
10.1359/jbmr.1997.12.7.1009
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发表时间：
1997-07-01
影响因子：
6.2
通讯作者：
Quarles, LD
中科院分区：
文献类型：
--
作者：
Guo, R;Quarles, LD
中性内肽酶PEX的失活突变已被确定为X连锁低磷血症（XLH）的原因。虽然PEX的功能尚不清楚，但目前的信息表明，XLH中肾磷酸盐保护受损是由于PEX未能降解一种不确定的磷酸尿因子或激活一种新的磷酸盐保护激素。XLH突变的生理学相关靶组织尚未确定，XLH中成骨细胞功能的明显内在缺陷暗示骨是PEX表达的可能位点。在当前的研究中，我们采用聚合酶链反应（PCR）策略从人骨细胞cDNA文库中扩增PEX cDNA，我们发现人PEX cDNA编码一个749个氨基酸的蛋白质，属于II型整合膜锌依赖性内肽酶家族，预测的PEX氨基酸序列与最近克隆的小鼠Per cDNA具有96.0%的同一性，并且与金属内肽酶家族的其他成员具有27-38%的同一性。采用逆转录酶（RT）-PCR与PEX特异性引物，我们检测到PEX转录在人骨肉瘤衍生的MG-63成骨细胞和分化的小鼠MC 3 T3-E1克隆成骨细胞，但没有在未成熟的MC 3 T3-E1前成骨细胞。XLH中骨矿化受损与成骨细胞中PEX的明显发育阶段特异性表达的相关性表明，骨是PEX表达的生理相关位点，PEX可能在成骨细胞介导的矿化中发挥积极作用。
Inactivating mutations of the neutral endopeptidase, PEX, have been identified as the cause of X-linked hypophosphatemia (XLH). Though the function of PEX is unknown, current information suggests that impaired renal phosphate conservation in XLH is due to the failure of PEX to either degrade an undefined phosphaturic factor or activate a novel phosphate-conserving hormone. The physiologically relevant target tissue for the XLH mutation has not been identified, An apparent intrinsic defect of osteoblast function in XLH implicates bone as a possible site of PEX expression, In the current investigation, we employed a polymerase chain reaction (PCR) strategy to amplify a PEX cDNA from a human bone cell cDNA library, We found that the human PEX cDNA encodes a 749 amino acid protein belonging to the type II integral membrane zinc-dependent endopeptidase family, The predicted PEX amino acid sequence shares 96.0% identity to the recently cloned mouse Per cDNA and has 27-38% identity to other members of the metalloendopeptidase family. Using reverse transcriptase (RT)-PCR with PEX-specific primers,,ve detected PEX transcripts in both human osteosarcoma-derived MG-63 osteoblasts and in differentiated mouse MC3T3-E1 clonal osteoblasts but not in immature MC3T3-E1 preosteoblasts. The association of impaired mineralization of bone in XLH and the apparent developmental stage-specific expression of PEX in osteoblasts suggest that bone is a physiologically relevant site of PEX expression and that PEX may play an active role in osteoblast-mediated mineralization.