Rand E B, Depaoli A M, Davidson N O, Bell G I, Burant C F
Howard Hughes Medical Institute, University of Chicago, Illinois 60637.
Am J Physiol. 1993 Jun;264(6 Pt 1):G1169-76. doi: 10.1152/ajpgi.1993.264.6.G1169.
cDNA clones encoding rat GLUT5-small intestinal facilitative hexose transporter were isolated from a jejunum library by cross-hybridization with a human GLUT5 cDNA probe. The cDNA sequence indicates that rat GLUT5 is composed of 502 amino acids and has 81.5% amino acid identity and 87.3% similarity with the sequence of human GLUT5. Expression of synthetic rat GLUT5 mRNA in Xenopus oocytes showed that rat GLUT5 was able to mediate the uptake of fructose and, to a lesser extent, of glucose. RNA blotting studies showed that GLUT5 mRNA was present in rat small intestine, kidney, and brain. Although GLUT5 mRNA is expressed in human testis, adipose tissue, and skeletal muscle, it could not be detected by RNA blotting in these rat tissues. Developmental studies showed low levels of GLUT5 mRNA in rat small intestine and kidney during the prenatal period with a rapid induction of GLUT5 expression occurring postnatally. In situ hybridization studies of GLUT5 mRNA expression in the small intestine revealed differential expression along the crypt-villus axis with the highest levels of mRNA being in the midvillus region. In addition, there was quantitatively more GLUT5 mRNA detected in the proximal as opposed to the distal small intestine.
通过与人GLUT5 cDNA探针进行交叉杂交，从空肠文库中分离出编码大鼠GLUT5（小肠易化性己糖转运蛋白）的cDNA克隆。cDNA序列表明，大鼠GLUT5由502个氨基酸组成，与人类GLUT5序列的氨基酸同一性为81.5%，相似性为87.3%。在非洲爪蟾卵母细胞中合成大鼠GLUT5 mRNA的表达表明，大鼠GLUT5能够介导果糖的摄取，在较小程度上也能介导葡萄糖的摄取。RNA印迹研究表明，GLUT5 mRNA存在于大鼠小肠、肾脏和大脑中。虽然GLUT5 mRNA在人类睾丸、脂肪组织和骨骼肌中表达，但在这些大鼠组织中通过RNA印迹无法检测到。发育研究表明，产前大鼠小肠和肾脏中的GLUT5 mRNA水平较低，出生后GLUT5表达迅速诱导。小肠中GLUT5 mRNA表达的原位杂交研究显示，沿隐窝-绒毛轴存在差异表达，mRNA水平最高的区域是绒毛中部。此外，与远端小肠相比，近端小肠中检测到的GLUT5 mRNA在数量上更多。
