Keller Matthew S, Ezaki Toshihiko, Guo Rong-Jun, Lynch John P
Division of Gastroenterology/660 CRB, University of Pennsylvania, 415 Curie Blvd., Philadelphia, PA 19104, USA.
Am J Physiol Gastrointest Liver Physiol. 2004 Jul;287(1):G104-14. doi: 10.1152/ajpgi.00484.2003. Epub 2004 Feb 19.
A mature columnar intestinal epithelium develops late in embryogenesis and is maintained throughout the life of the organism. Although the mechanisms driving intestine-specific gene expression have been well studied, those promoting the acquisition of cell-cell junctions, columnar morphogenesis, and polarization have been less studied. The Cdx homeodomain transcription factors (Cdx1 and Cdx2) regulate intestine-specific gene expression and intestinal epithelial differentiation. We report here that Cdx expression induces E-cadherin activity and cell-cell adhesion in human COLO 205 cancer cells. Within days of Cdx1 or Cdx2 expression, a new homotypic cell-cell adhesion phenotype is induced. This is a specific response to Cdx, inasmuch as a Cdx1 mutant failed to elicit the effect. Additionally, Cdx-expressing COLO 205 cells demonstrate a reduced proliferative capacity and an increase in the mRNA expression of differentiation-associated genes. Electron micrographs of these cells demonstrate induction of tight, adherens, and desmosomal junctions, as well as a columnar shape and apical microvilli. Investigations of the adhesion phenotype determined that it was Ca(2+) dependent and could be blocked by an E-cadherin-blocking antibody. However, E-cadherin protein levels and intracellular distribution were unchanged. Cdx expression restored the ability of the cell membranes to adhere and undergo compaction. We conclude that Cdx1 or Cdx2 expression is sufficient to induce an E-cadherin-dependent adhesion of COLO 205 cells. This adhesion is associated with polarization and cell-cell membrane compaction, as well as induction of a differentiated gene-expression pattern. Ascertaining the mechanism for this novel Cdx effect may yield insight into the development of mature colonic epithelium.
成熟的柱状肠上皮在胚胎发育后期形成，并在生物体的整个生命过程中得以维持。尽管驱动肠道特异性基因表达的机制已得到充分研究，但促进细胞间连接的形成、柱状形态发生和极化的机制却较少被研究。Cdx同源结构域转录因子（Cdx1和Cdx2）调节肠道特异性基因表达和肠上皮分化。我们在此报告，Cdx表达可诱导人COLO 205癌细胞中的E-钙黏蛋白活性和细胞间黏附。在Cdx1或Cdx2表达后的数天内，可诱导出一种新的同型细胞间黏附表型。这是对Cdx的特异性反应，因为Cdx1突变体未能引发这种效应。此外，表达Cdx的COLO 205细胞显示出增殖能力降低以及分化相关基因的mRNA表达增加。这些细胞的电子显微镜图像显示紧密连接、黏附连接和桥粒连接的诱导，以及柱状形态和顶端微绒毛的出现。对黏附表型的研究确定其依赖于Ca(2+)，并且可被E-钙黏蛋白阻断抗体阻断。然而，E-钙黏蛋白的蛋白水平和细胞内分布未发生改变。Cdx表达恢复了细胞膜黏附并发生紧密连接的能力。我们得出结论，Cdx1或Cdx2的表达足以诱导COLO 205细胞发生E-钙黏蛋白依赖性黏附。这种黏附与极化、细胞间细胞膜紧密连接以及分化基因表达模式的诱导相关。确定这种新型Cdx效应的机制可能有助于深入了解成熟结肠上皮的发育。
