一种新型单羧酸转运体基因的分离与克隆

Identification and Cloning of a Novel Monocarboxylate Transporter Gene

目的 分离、克隆编码肾脏甲酸盐 (formate)和 (或 )草酸盐 (oxalate)转运体的cDNA ,以研究Cl-在近端肾小管转运的机制。方法 根据细菌Oxlt(formate oxalate交换体 )的基因序列在哺乳动物表达序列标签 (expressse quencetag ,EST)数据库中查找与其相似的cDNA。按筛选到的cDNA设计探针 ,应用小鼠多组织杂交膜分析该基因的组织表达谱。结果 在小鼠肾cDNA文库中有一个与Oxlt极其相似的EST ,序列分析显示了其有一编码 4 2 9个氨基酸蛋白质的开放阅读框。从编码的顺序中可发现该序列与单羧酸转运家族 (monocarboxylatetransporter,MCT)极为相近 ,与小鼠MCT1的氨基酸一致性为 30 % ,与小鼠MCT2为 33% ,与大鼠MCT3为 2 9%。其中第 14～ 15 8个氨基酸中有 2 5 %与OxlT相同。Northern印迹发现 ,新的基因在小鼠肾脏中表达最多 ,肝脏和心脏中极少表达。结论 该基因是一新型的MCT家族成员 ,主要在肾脏中表达 。

Purpose To identify and clone the cDNAs encoding renal formate and (or) oxalate transporters in order to investigate the mechanism of Cl - reabsorption in the proximal tubule. Methods According to the sequence of a bacterial formate-oxalate exchanger(Oxlt),we tested whether the mammalian EST database contained a kidney cDNA with similarity to Oxlt.The gene was analyzed to locate the distribution with a mouse multiple tissues Northem blot. Results An EST with significant similarity to Oxlt was identified in a mouse renal cDNA library.The sequence of this EST clone had an open reading frame encoding a predicted protein of 429 amino acids.Database searching with the coding sequence revealed significant homology to the MCT family of monocarboxylate transporter(MCT).There were 33% identity with mouse MCT2,30% with mouse MCT1 and 29% with rat MCT3 in amino acid sequence.Amino acid 14-158 were 25% identical to the corresponding sequence of Oxlt.Northern blot analysis of mouse multiple tissue indicated that transcript encoding novel protein highly expressed in kidney.There were barely detectable expression in liver and heart. Conclusions A novel MCT family member with selection expression in the kidney was identified.It may be a candidate to mediate renal tubular formate transport.