Ni B, Rosteck P R, Nadi N S, Paul S M
Section on Molecular Pharmacology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1994 Jun 7;91(12):5607-11. doi: 10.1073/pnas.91.12.5607.
We have isolated a brain-specific cDNA that encodes a Na(+)-dependent inorganic phosphate (Pi) cotransporter (BNPI). The nucleotide sequence of BNPI predicts a protein of 560 amino acids with 6-8 putative transmembrane-spanning segments that is approximately 32% identical to the rabbit kidney Na(+)-dependent Pi cotransporter. Expression of BNPI mRNA in Xenopus oocytes results in Na(+)-dependent Pi transport similar to that reported for the recombinantly expressed or native kidney Na(+)-dependent cotransporter. RNA blot analysis reveals that BNPI mRNA is expressed predominantly (if not exclusively) in brain, and in situ hybridization histochemistry reveals BNPI transcripts in neurons of the cerebral cortex, hippocampus, and cerebellum. Furthermore, we have confirmed the presence of saturable Na(+)-dependent Pi cotransport in cultured cerebellar granule cells. Together, these data demonstrate the presence of a specific neuronal Na(+)-dependent transport system for Pi in brain.
我们分离出了一种脑特异性cDNA，它编码一种钠依赖性无机磷酸盐（Pi）共转运蛋白（BNPI）。BNPI的核苷酸序列预测其编码的蛋白质含有560个氨基酸，有6 - 8个推定的跨膜区段，与兔肾钠依赖性Pi共转运蛋白的同源性约为32%。BNPI mRNA在非洲爪蟾卵母细胞中的表达导致钠依赖性Pi转运，这与重组表达或天然肾钠依赖性共转运蛋白的情况类似。RNA印迹分析显示，BNPI mRNA主要（如果不是唯一）在脑中表达，原位杂交组织化学显示在大脑皮层、海马体和小脑的神经元中有BNPI转录本。此外，我们已经证实在培养的小脑颗粒细胞中存在可饱和的钠依赖性Pi共转运。这些数据共同证明了脑中存在一种特异性的神经元钠依赖性Pi转运系统。
