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

细胞响应细胞外基质的特异性而改变其表型和功能。我们现在报告的cDNA编码的蛋白激酶家族，它可以参与细胞基质相互作用的新成员的克隆和表征。从脂肪储存细胞（FSC）系获得的表达cDNA文库进行了筛选与针对大鼠肝细胞，这是应该包含基质受体的质膜部分制备的抗体。抗体与肝细胞窦状结构域上的蛋白质反应。从1.5 × 10^5个克隆中分离到11个克隆。11个克隆中有10个克隆来源于相同的mRNA，对应一种未知的蛋白质。最后测定了该基因6456 bp的核苷酸序列。该克隆预测的蛋白质在N端含有两个丝氨酸/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低于40%。在C-末端，其含有亮氨酸拉链结构域。该cDNA在新鲜分离和培养的FSC、内皮细胞和枯否细胞中识别7 kb的mRNA。相反，在肝细胞中未检测到该mRNA。该mRNA在培养的FSC中的表达出现下降。克隆的cDNA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.