Ogura Kiyoshi, Tai Tadashi
Department of Tumor Immunology, The Tokyo Metropolitan Organization for Medical Research, The Tokyo Metropolitan Institute of Medical Science, Japan.
Neurochem Res. 2002 Aug;27(7-8):779-84. doi: 10.1023/a:1020252823191.
A rat brain cDNA clone has been isolated using a eukaryotic cell transient expression system with anti-galactosylceramide (GalCer) monoclonal antibody (MAb), that induces GalCer expression in COS-7 cells. The protein was designated as GalCer expression factor-1 (GEF-1). The deduced amino acid sequences revealed a strikingly high homology to a mouse hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), but no homology to UDP-galactose: ceramide galactosyltransferase. COS-7 cells transfected with the cDNA clone showed dramatic morphological changes and cell growth suppression. Overexpression of GEF-1 in MDCK (MDCK/GEF-1) cells showed GalCer-derived sulfatide expression as well as morphological changes, but not cell growth suppression. The enzyme activity and the mRNA level of CGT increased significantly in MDCK/GEF-1 cells compared with control cells. Taking these results together, it is suggested that GEF-1 may play an important role in regulating GalCer and sulfatide expression in the epithelial cells as well as in the brain.
利用真核细胞瞬时表达系统和抗半乳糖基神经酰胺（GalCer）单克隆抗体（MAb）分离出了一个大鼠脑cDNA克隆，该抗体可诱导COS-7细胞中GalCer的表达。该蛋白质被命名为GalCer表达因子-1（GEF-1）。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（Hrs）具有极高的同源性，但与UDP-半乳糖：神经酰胺半乳糖基转移酶无同源性。用该cDNA克隆转染的COS-7细胞表现出显著的形态变化和细胞生长抑制。GEF-1在MDCK（MDCK/GEF-1）细胞中的过表达显示出GalCer衍生的硫脂表达以及形态变化，但没有细胞生长抑制。与对照细胞相比，MDCK/GEF-1细胞中CGT的酶活性和mRNA水平显著增加。综合这些结果，提示GEF-1可能在上皮细胞以及脑中调节GalCer和硫脂表达中起重要作用。
