Rao C N, Castronovo V, Schmitt M C, Wewer U M, Claysmith A P, Liotta L A, Sobel M E
Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland 20892.
Biochemistry. 1989 Sep 5;28(18):7476-86. doi: 10.1021/bi00444a047.
The high-affinity cellular receptor for the basement membrane component laminin is differentially expressed during tumor invasion and metastasis. A cDNA clone encoding the murine laminin receptor was isolated and identified on the basis of sequence homology to the human laminin receptor [Wewer et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 7137-7141]. Primer extension experiments demonstrated that the clone contained the complete 5' sequence of the murine laminin receptor mRNA. RNA blot data demonstrated a single-sized laminin receptor mRNA, approximately 1400 bases long, in human, mouse, and rat. The nascent laminin receptor predicted from the cDNA sequence is 295 amino acids long, with a molecular weight of 33,000, and contains one intradisulfide bridge, a short putative transmembrane domain, and an extracellular carboxy-terminal region which has abundant glutamic acid residues and multiple repeat sequences. The precursor of the laminin receptor is apparently smaller than the 67-kilodalton protein isolated from tissue. The apparent molecular weight on SDS-polyacrylamide gels of the rabbit reticulocyte cell-free translation product of selectively hybridized laminin receptor mRNA is 37,000. Antisera to three different domains of the cDNA-predicted receptor were used to study the relationship between the 37- and 67-kilodalton polypeptides. Antisera to cDNA-deduced synthetic peptides of the receptor immunoprecipitated a 37-kilodalton band both from cell-free translation products and from pulse-labeled cell extracts. On immunoblots of cell extracts, one antisynthetic peptide antiserum recognized only the 67-kilodalton receptor, while another antiserum identified both 37- and 67-kilodalton polypeptides, suggesting a precursor-product relationship between the two polypeptides.
基底膜成分层粘连蛋白的高亲和力细胞受体在肿瘤侵袭和转移过程中存在差异表达。基于与人层粘连蛋白受体的序列同源性，分离并鉴定了一个编码鼠层粘连蛋白受体的cDNA克隆[韦弗等人（1986年），《美国国家科学院院刊》83卷，7137 - 7141页]。引物延伸实验表明该克隆包含鼠层粘连蛋白受体mRNA完整的5'序列。RNA印迹数据显示在人、小鼠和大鼠中存在单一大小的层粘连蛋白受体mRNA，长度约为1400个碱基。从cDNA序列预测的新生层粘连蛋白受体长295个氨基酸，分子量为33,000，含有一个链内二硫键、一个短的假定跨膜结构域以及一个细胞外羧基末端区域，该区域有丰富的谷氨酸残基和多个重复序列。层粘连蛋白受体的前体明显小于从组织中分离出的67千道尔顿蛋白。选择性杂交的层粘连蛋白受体mRNA在兔网织红细胞无细胞翻译产物的SDS - 聚丙烯酰胺凝胶上的表观分子量为37,000。针对cDNA预测受体的三个不同结构域的抗血清用于研究37千道尔顿和67千道尔顿多肽之间的关系。针对受体cDNA推导的合成肽的抗血清从无细胞翻译产物和脉冲标记的细胞提取物中免疫沉淀出一条37千道尔顿的条带。在细胞提取物的免疫印迹上，一种抗合成肽抗血清仅识别67千道尔顿的受体，而另一种抗血清则识别37千道尔顿和67千道尔顿的多肽，这表明这两种多肽之间存在前体 - 产物关系。
