Sorokin L M, Pausch F, Frieser M, Kröger S, Ohage E, Deutzmann R
Institute for Experimental Medicine, University of Erlangen-Nürnburg, Schwabachanlage 10, 91045, Erlangen, Germany.
Dev Biol. 1997 Sep 15;189(2):285-300. doi: 10.1006/dbio.1997.8668.
We have previously shown that mouse and bovine endothelial cells express a novel 400-kDa laminin alpha chain complexed to beta1 and gamma1 laminin chains. We describe here purification of this laminin isoform from the conditioned medium of a mouse peripheral lymph node endothelial cell line, SVEC. The laminin alpha chain was isolated from the laminin complex, subjected to Edman digestion, and the amino acid sequences of the resulting peptides were determined. Amino acid sequence revealed 100% identity to the predicted amino acid sequence of the recently reported laminin alpha5 gene. A monoclonal antibody to the laminin alpha5 chain was raised (4G6), allowing investigation of its distribution in embryonic, newborn, and mature mouse tissues. The laminin alpha5 chain was expressed mainly by epithelial, endothelial, and myogenic cells: In both embryonic and mature tissues the laminin alpha5 chain was strongly expressed by epithelial cells, the bronchi of the lungs and the developing kidney tubules being the sites of strongest expression. However, laminin alpha5 was not associated with early stages of epithelial cell development, but rather with epithelial cell maturation. Widespread expression of laminin alpha5 in endothelial cells was apparent only in tissues of mature mice, its appearance correlating approximately with sexual maturity. During embryogenesis and in newborn tissues, laminin alpha5 occurred in basement membranes of larger blood vessels only, excluding a role in angiogenic processes. Smooth muscle and skeletal muscle cells were the only other cell types which showed considerable laminin alpha5 expression, with skeletal muscle exhibiting a developmentally regulated pattern of expression: The laminin alpha5 chain occurred in skeletal muscle fiber basement membranes early in embryogenesis (E13-E15) but decreased with development, remaining strongly expressed only at the neuromuscular junction. The data show that laminin alpha5 expression is associated with epithelial and endothelial cell maturation, implicating a role for this laminin chain in the maintenance of differentiated epithelial and endothelial cell phenotype.
我们之前已经表明，小鼠和牛的内皮细胞表达一种与β1和γ1层粘连蛋白链复合的新型400 kDa层粘连蛋白α链。我们在此描述从一种小鼠外周淋巴结内皮细胞系SVEC的条件培养基中纯化这种层粘连蛋白异构体。从层粘连蛋白复合物中分离出层粘连蛋白α链，进行埃德曼降解，然后测定所得肽段的氨基酸序列。氨基酸序列显示与最近报道的层粘连蛋白α5基因的预测氨基酸序列100%相同。制备了一种针对层粘连蛋白α5链的单克隆抗体（4G6），从而能够研究其在胚胎、新生和成熟小鼠组织中的分布。层粘连蛋白α5链主要由上皮细胞、内皮细胞和成肌细胞表达：在胚胎和成熟组织中，上皮细胞都强烈表达层粘连蛋白α5链，肺支气管和发育中的肾小管是表达最强的部位。然而，层粘连蛋白α5与上皮细胞发育的早期阶段无关，而是与上皮细胞成熟有关。层粘连蛋白α5在内皮细胞中的广泛表达仅在成熟小鼠的组织中明显，其出现时间大约与性成熟相关。在胚胎发育过程中和新生组织中，层粘连蛋白α5仅出现在较大血管的基底膜中，排除其在血管生成过程中的作用。平滑肌和骨骼肌细胞是仅有的其他显示出大量层粘连蛋白α5表达的细胞类型，骨骼肌呈现出发育调控的表达模式：层粘连蛋白α5链在胚胎发育早期（E13 - E15）出现在骨骼肌纤维基底膜中，但随着发育而减少，仅在神经肌肉接头处仍强烈表达。数据表明层粘连蛋白α5的表达与上皮细胞和内皮细胞成熟相关，暗示该层粘连蛋白链在维持分化的上皮细胞和内皮细胞表型中起作用。
