Molecular cloning and characterization of galactosylceramide expression factor-1 (GEF-1).
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.
Ogura
Kiyoshi
K
Department of Tumor Immunology, The Tokyo Metropolitan Organization for Medical Research, The Tokyo Metropolitan Institute of Medical Science, Japan.
Tai
Tadashi
T
D000251:Adenosine Triphosphatases; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D056827:Endosomal Sorting Complexes Required for Transport; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D051381:Rats
D018076:DNA, Complementary; D056827:Endosomal Sorting Complexes Required for Transport; D010750:Phosphoproteins; D000251:Adenosine Triphosphatases; C115505:Hgs protein, rat