Ogura K, Kohno K, Tai T
Department of Tumor Immunology, Tokyo Metropolitan Institute of Medical Science, Japan.
J Neurochem. 1998 Nov;71(5):1827-36. doi: 10.1046/j.1471-4159.1998.71051827.x.
A rat brain cDNA clone has been isolated, using a eukaryotic cell transient expression system in conjunction with an anti-galactosylceramide (anti-GalCer) monoclonal antibody that induces GalCer expression in COS-7 cells. The protein was designated as GalCer expression factor-1 (GEF-1). A good correlation between GalCer expression and the level of the enzyme activity of UDP-galactose:ceramide galactosyltransferase (CGT) was demonstrated. The cDNA insert encoded a polypeptide of 771 amino acids with a calculated molecular mass of 85,787 Da. The cDNA hybridized to a single mRNA of 3.1 kb in all rat organs examined, including brain, testis, and skeletal muscle. The cDNA product was determined to be a tyrosine-phosphorylated protein with a molecular mass of 110 kDa in transfected COS-7 cells and adult rat brain. COS-7 cells transfected with the cDNA clone showed dramatic morphological changes: The transfected cells appeared to be fibroblast-like cells, whereas the parent COS-7 cells were typical epithelial-like cells. The deduced amino acid sequences revealed a strikingly high homology to a mouse hepatocyte growth factor-regulated tyrosine kinase substrate but no homology to CGT. Taking these results together, it is suggested that GEF-1 may play an important role in regulating GalCer expression in the brain.
利用真核细胞瞬时表达系统，结合一种能在COS-7细胞中诱导半乳糖基神经酰胺（GalCer）表达的抗半乳糖基神经酰胺单克隆抗体，分离出了一个大鼠脑cDNA克隆。该蛋白被命名为GalCer表达因子-1（GEF-1）。研究表明，GalCer表达与UDP-半乳糖：神经酰胺半乳糖基转移酶（CGT）的酶活性水平之间存在良好的相关性。cDNA插入片段编码一个由771个氨基酸组成的多肽，计算分子量为85,787道尔顿。在所有检测的大鼠器官（包括脑、睾丸和骨骼肌）中，该cDNA与一个3.1 kb的单一mRNA杂交。在转染的COS-7细胞和成年大鼠脑中，cDNA产物被确定为一种分子量为110 kDa的酪氨酸磷酸化蛋白。用该cDNA克隆转染的COS-7细胞表现出显著的形态变化：转染细胞看起来像成纤维细胞样细胞，而亲本COS-7细胞是典型的上皮样细胞。推导的氨基酸序列显示与小鼠肝细胞生长因子调节的酪氨酸激酶底物具有极高的同源性，但与CGT没有同源性。综合这些结果，提示GEF-1可能在调节脑中GalCer表达方面发挥重要作用。
