Braga V M, Hajibagheri N, Watt F M
Keratinocyte Laboratory, Imperial Cancer Research Fund, London, England.
Cell Adhes Commun. 1998 Mar;5(2):137-49. doi: 10.3109/15419069809040287.
On initiation of terminal differentiation human epidermal keratinocytes detach from the underlying basement membrane as a result of inactivation and subsequent loss of integrins from the cell surface. Assembly of keratinocytes into multilayered sheets requires functional E- and P-cadherin and when stratification is inhibited in low calcium medium differentiating keratinocytes continue to express functional integrins. Using immunofluorescence microscopy, we found that on addition of calcium ions to keratinocyte monolayers there was colocalisation of the beta 1 integrins and E-cadherin along the lateral membranes except for a zone close to the substratum which exclusively contained integrins. Quantitative immunoelectron microscopy showed that on induction of stable cell-cell contacts the density of beta 1 integrins was the same on the apical and lateral membranes, suggesting that the accumulation of integrins on the lateral membranes observed by immunofluorescence microscopy is due to the increased area of contact between adjacent cells and not to an increase in receptor density. There were no changes in the levels of catenins and their degree of phosphorylation after induction of cell-cell contacts. These observations provide new sights into the mechanism of calcium-dependent intercellular adhesion of keratinocytes.
在终末分化开始时，人类表皮角质形成细胞由于整合素在细胞表面失活并随后丢失，从而与下方的基底膜分离。角质形成细胞组装成多层薄片需要功能性的E-钙黏蛋白和P-钙黏蛋白，并且当在低钙培养基中抑制分层时，分化的角质形成细胞继续表达功能性整合素。利用免疫荧光显微镜，我们发现向角质形成细胞单层中添加钙离子后，β1整合素和E-钙黏蛋白沿侧膜共定位，但靠近基质的区域除外，该区域仅含有整合素。定量免疫电子显微镜显示，在诱导稳定的细胞间接触时，β1整合素在顶端膜和侧膜上的密度相同，这表明免疫荧光显微镜观察到的侧膜上整合素的积累是由于相邻细胞间接触面积增加，而不是受体密度增加。诱导细胞间接触后，连环蛋白的水平及其磷酸化程度没有变化。这些观察结果为角质形成细胞钙依赖性细胞间黏附机制提供了新的见解。
