Hypophosphatemia : cDNA cloning of a Na^+-dependent phosphate co-transporter from human kidney

低磷血症：从人肾中克隆 Na+ 依赖性磷酸盐协同转运蛋白的 cDNA

基本信息

批准号：
05670145
负责人：
MIYAMOTO Kenichi
金额：
$ 1.34万
依托单位：
Tokushima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Hypophosphatemic vitamin D-resistant rickets is the most common form of hypophosphatemic rickets in humans. It is characterized by low renal tubular reabsorption of phosphate, low plasma phosphate, absence of elevated 1,25-dihydroxy-vitamine D despite the presence of hypophosphatemia and osteomalacic bone disease. In the present study, a cDNA (NPT-1) encoding a protein 69% identical in amino acid sequence to that of the Na/Pi cotransporter NaPi-1 was isolated from a human kidney library. Injected of RNA transcribed from this clone, NPT-1, into Xenopus oocuytes results in expression of a Na/Pi cotransport activity with high affinity for transport (Km=0.29mM). Kinetic characterization ([Pi], [Na]) showed that expressed transport activity has properties similar to that of oocytes injected juman kidney poly (A)^+RNA.Northern blotting showes that NPT-1 mRNA is expressed in kidney cortex, liver and brain but not in other tissues. Hybrid depletion with antisense oligonucleotide of NaPi-3 and NPT-1 completely inhibited poly(A)^+RNA-induced Na^+-dependent phosphate uptake in oocytes. These finding indicate that two high affinity Na/Pi cotransporter (NaPi-3 and NPT-1) are present in human kidney cortex.NPT-1 maps the location to human chromosome 6. NaPi-3 maps the location to human chromosome 5. The role of high affinity Na/Pi cotransporter in Hereditary Hypophosphatemic Rickets with Hypercarciuria (HHRH) which is autosomally inherited disorder and caused by defective reabsorption of Pi in the proximal tubule of the kidney is under study.

抗磷酸化维生素D-耐药的易能是人类下磷酸ri鼠的最常见形式。它的特征是磷酸肾小管较低，血浆低磷酸盐，尽管存在低磷酸血症和骨呈骨骨病，但不存在升高的1,25-二羟基 - 维化明D。在本研究中，从人类肾脏文库中分离出与Na/pi cotransporter napi-1的氨基酸序列中编码69％蛋白质的cDNA（NPT-1）。从该克隆（NPT-1）转录到爪蟾卵巢中的RNA注射，导致表达具有高亲和力的Na/pi cotransport活性（km = 0.29mm）。动力学表征（[PI]，[Na]）表明，表达的运输活性具有类似于注射的卵母细胞的特性，注射的juman肾脏poly（a）^+rna.northern斑点表明，NPT-1 mRNA在肾脏皮质，肝脏和大脑中表达，但在其他组织中则不表达。 NAPI-3和NPT-1的反义寡核苷酸的杂化耗竭完全抑制了卵母细胞中的poly（a）^+RNA诱导的Na^+ - 依赖性磷酸摄取。这些发现表明，人类肾脏皮层中存在两个高亲和力Na/pi cotransporter（NAPI-3和NPT-1）。NPT-1映射到人类染色体6。NAPI-3将人类染色体的位置映射到人类染色体的位置。正在研究肾脏近端小管中PI的遗传障碍和引起的疾病。