Madsen P, Rasmussen H H, Flint T, Gromov P, Kruse T A, Honoré B, Vorum H, Celis J E
Department of Medical Biochemistry, University of Aarhus, Denmark.
J Biol Chem. 1995 Mar 17;270(11):5823-9. doi: 10.1074/jbc.270.11.5823.
The galectins are a family of beta-galactoside-binding proteins implicated in modulating cell-cell and cell-matrix interactions. Here we report the cloning and expression of a novel member of this family (galectin-7) that correspond to IEF (isoelectric focusing) 17 (12,700 Da; pI, 7.6) in the human keratinocyte protein data base, and that is strikingly down-regulated in SV40 transformed keratinocytes (K14). The cDNA was cloned from a lambda gt11 cDNA expression library using degenerated oligodeoxyribonucleotides back-translated from an IEF 17 peptide sequence. The protein encoded by the galectin-7 clone comigrated with IEF 17 as determined by two-dimensional (two-dimensional gel electrophoresis) analysis of proteins expressed by transiently transfected COS-1 cells, and bound lactose. Alignment of the amino acid sequences with other members of the family showed that the amino acids central to the beta-galactoside interaction are conserved. Galectin-7 was partially externalized to the medium by keratinocytes although it has no typical secretion signal peptide. Immunoblotting as well as immunofluorescence analysis of human tissues with a specific galectin-7 antibody revealed a narrow distribution of the protein which was found mainly in stratified squamous epithelium. The antigen localized to basal keratinocytes, although it was also found, albeit at lower levels, in the suprabasal layers where it concentrated to areas of cell to cell contact. Both, its cellular localization as well as its striking down-regulation in K14 keratinocytes imply a role in cell-cell and/or cell-matrix interactions necessary for normal growth control. The galectin-7 gene was mapped to chromosome 19.
半乳糖凝集素是一族β-半乳糖苷结合蛋白，参与调节细胞间和细胞与基质间的相互作用。在此，我们报告该家族一个新成员（半乳糖凝集素-7）的克隆与表达，它对应于人角质形成细胞蛋白质数据库中的IEF（等电聚焦）17（12,700 Da；pI，7.6），并且在SV40转化的角质形成细胞（K14）中显著下调。使用从IEF 17肽序列反向翻译的简并寡脱氧核苷酸，从λgt11 cDNA表达文库中克隆出该cDNA。通过对瞬时转染的COS-1细胞表达的蛋白质进行二维（二维凝胶电泳）分析确定，半乳糖凝集素-7克隆编码的蛋白质与IEF 17迁移一致，且能结合乳糖。该氨基酸序列与家族其他成员的比对显示，β-半乳糖苷相互作用的核心氨基酸是保守的。尽管半乳糖凝集素-7没有典型的分泌信号肽，但角质形成细胞可将其部分分泌到培养基中。用特异性半乳糖凝集素-七抗体对人体组织进行免疫印迹及免疫荧光分析显示，该蛋白分布狭窄，主要见于复层鳞状上皮。抗原定位于基底角质形成细胞，尽管在上皮上层也有发现，但其水平较低，且集中在细胞间接触区域。其细胞定位以及在K14角质形成细胞中的显著下调，均表明它在正常生长控制所需的细胞间和/或细胞与基质间相互作用中发挥作用。半乳糖凝集素-7基因定位于19号染色体。
