Cloning and characterization of a possible adhesion molecule expressed by hepatic non-parenchymal cells

细胞因细胞外基质的特异性而改变其表型和功能。我们现在报道了一个编码蛋白-激酶家族新成员的基因的克隆和鉴定，该基因可以参与细胞-基质相互作用。用一种抗大鼠肝细胞质膜组分的抗体筛选从储脂细胞(FSC)获得的表达文库，该抗体被认为含有基质受体。该抗体与定位于肝细胞正弦波结构域的蛋白质发生反应。从1.5×10~(-5)噬菌体中分离到11个克隆。11个克隆中有10个来自相同的mRNA，对应着一个未知的蛋白质。最后测定了6456bp的核苷酸序列。该克隆的预测蛋白在N端含有两个拷贝的丝氨酸/苏氨酸蛋白激酶结构域，与已报道的蛋白激酶催化结构域的同源性不到40%。在C末端，它含有一个亮氨酸拉链结构域。该基因在新鲜分离和培养的FSC、内皮细胞和Kupffer细胞中识别7kb的mRNA。相反，该基因在肝细胞中未检测到。在培养的FSC中，该基因的表达呈下降趋势。克隆的cDNAs的功能目前正在研究中。

Cells change their phenotype and functions in response to the specificity of the extracellular matrix. We now report the cloning and characterization of a cDNA encoding a new member of the protein-kinase family, which can be involved in the cell-matrix interaction. The expression cDNA library obtained from a fat-storing cell (FSC) line was screened with an antibody prepared against a plasma membrane fraction of rat hepatocytes, which was supposed to contain the matrix receptor. The antibody reacted with a protein localized on the sinusoidal domain of hepatocytes. It also recognized various proteins synthesized by FSC.From 1.5x10^5 phages, 11 clones were isolated. Ten of the 11 clones derived from the same mRNA corresponding an unkown protein. Finally, we dtermined the nucleotide sequence of 6456bp. The predicted protein of this clone had two copies of serine/threonine protein-kinase domains in N-terminal end, which showed less than 40% homology with catalytic domains of previously reported protein kinases. In the C-terminus, it contained a leucine zipper domain. The cDNA recognized a 7kb mRNA in freshly isolated and cultured FSC,endothelial and Kupffer cells. In contrast, this mRNA was not detected in hepatocytes. The expression of this mRNA appeared to decrease in cultured FSC.The function of the cloned cDNA is currently under investigation.