Vachon P H, Perreault N, Magny P, Beaulieu J F
Département d'Anatomie et de Biologie Cellulaire, Faculté de Médecine, Université de Sherbrooke, Québec, Canada.
J Cell Physiol. 1996 Jan;166(1):198-207. doi: 10.1002/(SICI)1097-4652(199601)166:1<198::AID-JCP21>3.0.CO;2-A.
The heterogenous expression of brush border membrane hydrolases by the human enterocyte-like Caco-2 cell line during morphological and functional differentiation in vitro was investigated at the cellular level. Indirect immunofluorescence revealed that the heterogeneous ("mosaic") expression of sucrase-isomaltase, lactase, aminopeptidase N, and alkaline phosphatase was, in fact, transient in nature. The labeling indexes for each hydrolase gradually increased during culture at postconfluence in order to reach a maximum (> or = 90%) after 30 days, concomitant with an upregulation of their respective protein expression levels. In contrast, dipeptidylpeptidase IV labeling remained relatively constant. Backscattered electron imaging analysis in midstage (12 days postconfluence) monolayers demonstrated a lack of correlation between brush border membrane development and expression of each enzyme studied. Moreover, double immunostaining revealed that none of the other four hydrolases correlated directly with sucrase-isomaltase expression. Finally, immunodetection for the proliferation-associated antigen KI-67 revealed a transient mosaic pattern of proliferation which was inversely related to Caco-2 cell differentiation. These data indicate that enterocytic differentiation-related (as well as proliferation-related) gene expression in Caco-2 cells is regulated but uncoordinated at the cellular level, suggesting that an overall control mechanism is lacking.
在体外形态学和功能分化过程中，在细胞水平上研究了人肠上皮样Caco-2细胞系刷状缘膜水解酶的异质性表达。间接免疫荧光显示，蔗糖酶-异麦芽糖酶、乳糖酶、氨肽酶N和碱性磷酸酶的异质性（“镶嵌”）表达实际上是短暂的。在汇合后培养期间，每种水解酶的标记指数逐渐增加，以便在30天后达到最大值（≥90%），同时其各自蛋白质表达水平上调。相比之下，二肽基肽酶IV标记保持相对恒定。中期（汇合后12天）单层的背散射电子成像分析表明，刷状缘膜发育与所研究的每种酶的表达之间缺乏相关性。此外，双重免疫染色显示，其他四种水解酶中没有一种与蔗糖酶-异麦芽糖酶表达直接相关。最后，对增殖相关抗原KI-67的免疫检测显示增殖的短暂镶嵌模式，这与Caco-2细胞分化呈负相关。这些数据表明，Caco-2细胞中肠上皮细胞分化相关（以及增殖相关）的基因表达在细胞水平上受到调控但不协调，这表明缺乏整体控制机制。
