THE HUMAN KIDNEY LOW-AFFINITY NA+/GLUCOSE COTRANSPORTER SGLT2 - DELINEATION OF THE MAJOR RENAL REABSORPTIVE MECHANISM FOR D-GLUCOSE
THE HUMAN KIDNEY LOW-AFFINITY NA+/GLUCOSE COTRANSPORTER SGLT2 - DELINEATION OF THE MAJOR RENAL REABSORPTIVE MECHANISM FOR D-GLUCOSE
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DOI：
10.1172/jci116972
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发表时间：
1994-01-01
影响因子：
15.9
通讯作者：
HEDIGER, MA
中科院分区：
文献类型：
--
作者：
KANAI, Y;LEE, WS;HEDIGER, MA
已知d -葡萄糖在肾脏中的主要重吸收机制涉及低亲和力高容量Na+/葡萄糖共转运体，该转运体位于早期近曲小管段S1，其Na+与葡萄糖偶联比为1:1。在这里，我们为肾d -葡萄糖重吸收机制提供了第一个分子证据。我们报道了先前克隆的人类肾脏cDNA的特性，该cDNA编码的蛋白质与高亲和力Na+/葡萄糖共转运蛋白（SGLT1）具有59%的一致性。通过对非洲非洲蟾卵母细胞的表达研究，我们证明了这种蛋白（称为SGLT2）介导饱和Na+依赖的d -葡萄糖和α -甲基-d -葡萄糖苷（α MeGlc）的转运，α MeGle的K-m值为1.6 mM， Na+的K-m值为250 - 300 mM，与低亲和力Na+/葡萄糖共转运一致。与SGLT1相反，SGLT2不转运d -半乳糖。通过比较[14C]- α MeGIc摄取的初始速率与由α meglc诱发的内向电流计算的Na+内流，我们发现SGLT2的Naf -葡萄糖偶联比。是1:1。结合原位杂交和免疫细胞化学与小管片段特异性标记抗体，我们证明了SGLT2信息在近端小管S1片段中具有极高的水平。这种表达水平在Northern印迹上也很明显，可能赋予了这种葡萄糖运输系统高容量。我们得出结论，SGLT2具有肾低亲和力高容量Na+/葡萄糖共转运体的特性，如先前报道的灌注小管制剂和刷状边界膜囊泡。了解这种主要的肾Na+/葡萄糖重吸收机制的结构和功能特性，将促进我们对家族性肾性尿糖症和糖尿病肾病等肾脏疾病的病理生理学的理解。
The major reabsorptive mechanism for D-glucose in the kidney is known to involve a low affinity high capacity Na+/glucose cotransporter, which is located in the early proximal convoluted tubule segment S1, and which has a Na+ to glucose coupling ratio of 1:1. Here we provide the first molecular evidence for this renal D-glucose reabsorptive mechanism. We report the characterization of a previously cloned human kidney cDNA that codes for a protein with 59% identity to the high affinity Na+/glucose cotransporter (SGLT1). Using expression studies with Xenopus laevis oocytes we demonstrate that this protein (termed SGLT2) mediates saturable Na+-dependent and phlorizin-sensitive transport of D-glucose and alpha-methyl-D-glucopyranoside (alpha MeGlc) with K-m values of 1.6 mM for alpha MeGle and similar to 250 to 300 mM for Na+, consistent with low affinity Na+/glucose cotransport. In contrast to SGLT1, SGLT2 does not transport D-galactose. By comparing the initial rate of [14C]-alpha MeGIc uptake with the Na+-influx calculated from alpha MeGlc-evoked inward currents, we show that the Naf to glucose coupling ratio of SGLT2. is 1:1. Using combined in situ hybridization and immunocytochemistry with tubule segment specific marker antibodies, we demonstrate an extremely high level of SGLT2 message in proximal tubule S1 segments. This level of expression was also evident on Northern blots and likely confers the high capacity of this glucose transport system. We conclude that SGLT2 has properties characteristic of the renal low affinity high capacity Na+/glucose cotransporter as previously reported for perfused tubule preparations and brush border membrane vesicles. Knowledge of the structural and functional properties of this major renal Na+/glucose reabsorptive mechanism will advance our understanding of the pathophysiology of renal diseases such as familial renal glycosuria and diabetic renal disorders.