Cohen M B, Mann E A, Lau C, Henning S J, Giannella R A
Children's Hospital Medical Center, Cincinnati, OH 45229.
Biochem Biophys Res Commun. 1992 Jul 15;186(1):483-90. doi: 10.1016/s0006-291x(05)80833-2.
Binding of Escherichia coli heat-stable enterotoxin to its receptor is critical to the initiation of toxin-induced secretion and diarrheal disease; it is also likely, however, that this receptor binds an endogenous ligand. In order to characterize the expression of the heat-stable enterotoxin receptor in the small intestine, we isolated epithelial cells from villus tip to crypt in rat jejunum and ileum. Binding of radiolabeled toxin was maximal in the villus preparations and gradually decreased along the villus-to-crypt axis, paralleling the decline of sucrase activity. Northern blots of total RNA identified a single heat stable enterotoxin receptor transcript (3.8 kb), predominantly in the villus cell fractions. In situ hybridization demonstrated clear signal in the villus cells with no apparent signal in the crypt cells, lamina propria or muscularis. Expression of this receptor was greatest after enterocytes leave the proliferative cycle and enter villi. This pattern of gene and protein expression may reflect a role of this receptor in binding endogenous ligands which in turn may regulate intestinal ion flux along the villus-to-crypt axis.
大肠杆菌热稳定肠毒素与其受体的结合对于毒素诱导的分泌和腹泻病的起始至关重要；然而，这种受体也可能结合一种内源性配体。为了表征热稳定肠毒素受体在小肠中的表达，我们从大鼠空肠和回肠的绒毛顶端到隐窝分离出上皮细胞。放射性标记毒素的结合在绒毛制剂中最大，并沿绒毛到隐窝轴逐渐降低，这与蔗糖酶活性的下降平行。总RNA的Northern印迹鉴定出一个单一的热稳定肠毒素受体转录本（3.8 kb），主要存在于绒毛细胞组分中。原位杂交显示绒毛细胞中有清晰信号，而隐窝细胞、固有层或肌层中无明显信号。这种受体的表达在肠上皮细胞离开增殖周期并进入绒毛后最大。这种基因和蛋白质表达模式可能反映了该受体在结合内源性配体中的作用，而内源性配体反过来可能调节沿绒毛到隐窝轴的肠道离子通量。
