Custer M, Spindler B, Verrey F, Murer H, Biber J
Institute of Physiology, University of Zurich, Switzerland.
Am J Physiol. 1997 Nov;273(5):F801-6. doi: 10.1152/ajprenal.1997.273.5.F801.
Chronic restriction of dietary Pi elicits an increased reabsorption of Pi in the kidney proximal tubules, which involves a stimulation of apical Na-Pi cotransport. This adaptation is in part a direct cellular response of which the mechanism(s) are poorly understood. In this study, the impact of dietary Pi restriction on the differential expression of rat kidney cortex mRNAs was visualized to identify gene products regulated by the Pi status. When kidney cortex mRNAs of rats fed a low- or a high-Pi diet were compared by differential display-polymerase chain reaction (DD-PCR), thirty modulated cDNA bands were observed, of which four were confirmed as being regulated. We focused on one of the upregulated bands, dietary Pi-regulated RNA-1 (diphor-1). A cDNA containing an open reading frame encoding a 52-kDa protein was cloned by library screening. Diphor-1 exhibits a high degree of identity to the Na/H exchanger regulatory factor and to a tyrosine kinase activating protein. Highest expression of diphor-1 mRNA was detected in the kidney (proximal tubules) and in small intestine. Expression experiments showed that diphor-1 specifically increases Na-Pi cotransport in oocytes of Xenopus laevis coinjected with renal type II Na-Pi contransporter cRNA. Further characterizations of diphor-1 will show whether diphor-1 is primarily or secondarily involved in the response to dietary Pi.
长期限制饮食中的磷会导致肾近端小管对磷的重吸收增加，这涉及到顶端钠-磷共转运体的激活。这种适应性变化部分是一种直接的细胞反应，但其机制尚不清楚。在本研究中，通过观察饮食中磷限制对大鼠肾皮质mRNA差异表达的影响，以鉴定受磷状态调节的基因产物。当通过差异显示-聚合酶链反应（DD-PCR）比较喂食低磷或高磷饮食的大鼠的肾皮质mRNA时，观察到30条调节的cDNA条带，其中4条被确认为受调节。我们聚焦于其中一条上调的条带，即饮食磷调节RNA-1（diphor-1）。通过文库筛选克隆了一个包含编码52 kDa蛋白的开放阅读框的cDNA。Diphor-1与钠/氢交换调节因子以及酪氨酸激酶激活蛋白具有高度同源性。在肾脏（近端小管）和小肠中检测到diphor-1 mRNA的最高表达。表达实验表明，diphor-1可特异性增加与肾II型钠-磷共转运体cRNA共注射的非洲爪蟾卵母细胞中的钠-磷共转运。对diphor-1的进一步表征将显示其是否主要或次要参与对饮食中磷的反应。
