Analysis of cellular functions of cells transfected with sense or antisense β-1,4-galactosyltransferase cDNA

哺乳动物细胞中含有多种β-1半乳糖基转移酶(、-1，4-Galts，β-1，4-Galts)，参与糖蛋白的生物合成。当细胞转化时，它们在蛋白质上表达与肿瘤相关的碳水化合物抗原的高度分支糖链，这对细胞的致瘤性和转移至关重要。在转化过程中，β-1，4-Galts I、III、IV和VI的基因表达水平没有变化，而β-1，4-GalT II的基因表达水平下降，β-1，4-GalT V的基因表达水平上升。为了研究β-1，4-GalT II和V形成的碳水化合物的生物学意义，将它们的基因导入几个细胞系。将β-1，4-GalT II-正义或β-1，4-GalT V-反义基因导入小鼠黑色素瘤F10细胞，通过凝集素印迹分析检测到细胞膜糖蛋白糖基化的改变。将该细胞接种于C57B小鼠体内，检测其成瘤能力。小鼠黑色素瘤F10细胞在动物体内形成肿瘤，而转导β-1，4-GalT II-正义或β-1，4-GalT V-反义基因的F10细胞不能或生长缓慢。这些结果表明，β-1，4-GalTS II和V合成的糖链参与了细胞生长调控机制。有必要进行进一步的研究，以确定哪些碳水化合物结构真正参与了这一生物事件。

Mammalian cells are now shown to contain several β-1、4-galactosyltransferases (β-1,4-GalTs) which are involved in the biosynthesis of glycoprotein. When cells are transformed, they express the highly branched sugar chains with tumor-associated carbohydrate antigens on proteins which are critical to tumorigenicity and metastasis of the cell. During transformation, the gene expression levels of β-1,4-GalTs I, III, IV and VI were not changed while that of β-1,4-GalT II decreased and that of β-1,4-GalT V increased. In order to investigate biological significance of the carbohydrates formed by β-1,4-GalT II and V, their genes were introduced into several cell lines. When β-1,4-GalT II-sense cDNA or β-1,4-GalT V-antisense cDNA was transfected into mouse melanoma F10 cells, altered glycosylation of the membrane glycoproteins was detected by lectin blot analysis. The cells were inoculated into C57B mouse and the ability to form tumors were examined. Mouse melanoma F10 cells formed tumors in the animals while those transfected with β-1,4-Galt II-sense cDNA or β-1,4-GalT V-antisense cDNA failed or developed tumors very slowly. These results indicated that the sugar chains synthesized by β-1,4-GalTs II and V are involved in the growth control mechanism of cells. Further studies are necessary to identify which carbohydrate structures are really engaged in this biological event.