Stamatoglou S C, Sullivan K H, Johansson S, Bayley P M, Burdett I D, Hughes R C
National Institute for Medical Research, London, UK.
J Cell Sci. 1990 Dec;97 ( Pt 4):595-606. doi: 10.1242/jcs.97.4.595.
We have compared the localization of integrin alpha 5 beta 1 and AGp110 (apical glycoprotein of Mr 110 x 10(3]] in rat liver parenchyma and in primary hepatocyte cultures. Integrin alpha 5 beta 1 is a heterodimeric fibronectin receptor. AGp110 is a newly described monomeric glycoprotein of the apical (bile canalicular) membrane domain of liver parenchyma that binds in an RGD-independent manner to fibronectin and mediates spreading of hepatocytes onto fibronectin-coated substrata. Using Western blotting of fractionated liver membranes and immunocytochemistry of liver sections at light- and electron-microscope levels, we have confirmed that AGp110 is a canalicular glycoprotein and have established that integrin is located in approximately equal proportions in the sinusoidal, lateral and canalicular membrane domains. In the canalicular surface domain both glycoproteins are associated with microvilli. Examination of immunolabelled primary hepatocytes spread on fibronectin-coated substrata by light and laser scanning confocal microscopy revealed colocalization of AGp110, integrin, actin and vinculin in substratum-attached microextensions at the periphery of the basal cell surface. Actin filaments that terminated at these cell processes originated from circular sub-cortical actin fibres. Interference reflection microscopy revealed focal adhesive contacts at the edge of the basal cell periphery at the same location where AGp110 and integrin were observed by immunofluorescence. In vitro, a proportion of the primary hepatocytes seeded onto fibronectin-coated substrata aggregated into colonies of several cells with intercellular contacts between neighbouring cells. Cell-substratum contacts containing integrin, AGp110, actin and vinculin followed the contours of these colonies in the same manner as they delineated the basal periphery of single, substratum-attached cells. We conclude that both integrin and AGp110 contribute to hepatocyte-fibronectin adhesive interactions and that intercellular adhesion and cooperation among hepatocytes in their response to fibronectin matrices leads to colony formation and morphological differentiation of parenchymal cell monolayers in vitro.
我们比较了整合素α5β1和AGp110（分子量为110×10³的顶端糖蛋白）在大鼠肝实质和原代肝细胞培养物中的定位。整合素α5β1是一种异二聚体纤连蛋白受体。AGp110是肝实质顶端（胆小管）膜结构域新描述的单体糖蛋白，它以不依赖RGD的方式与纤连蛋白结合，并介导肝细胞在纤连蛋白包被的基质上的铺展。通过对分离的肝细胞膜进行蛋白质印迹分析以及在光镜和电镜水平对肝切片进行免疫细胞化学分析，我们证实AGp110是一种胆小管糖蛋白，并确定整合素在肝血窦、侧面和胆小管膜结构域中的分布比例大致相等。在胆小管表面结构域，这两种糖蛋白都与微绒毛相关。通过光镜和激光扫描共聚焦显微镜检查铺展在纤连蛋白包被基质上的免疫标记原代肝细胞，发现AGp110、整合素、肌动蛋白和纽蛋白在基底细胞表面周边附着于基质的微突起中共定位。终止于这些细胞突起的肌动蛋白丝起源于环形的皮质下肌动蛋白纤维。干涉反射显微镜显示，在通过免疫荧光观察到AGp110和整合素的相同位置，基底细胞周边边缘存在粘着斑接触。在体外，接种到纤连蛋白包被基质上的一部分原代肝细胞聚集成由几个细胞组成的集落，相邻细胞之间存在细胞间接触。含有整合素、AGp110、肌动蛋白和纽蛋白的细胞与基质接触沿着这些集落的轮廓分布，方式与它们勾勒单个附着于基质的细胞的基底周边相同。我们得出结论，整合素和AGp110都有助于肝细胞与纤连蛋白的粘附相互作用，并且肝细胞在对纤连蛋白基质的反应中的细胞间粘附与合作导致了体外实质细胞单层的集落形成和形态分化。
