Purification and structural characterization of de-N-acetylated form of GD3 ganglioside present in human melanoma tumors.
The presence of gangliosides containing de-N-acetylated sialic acids in human tissues has been so far shown by using mouse monoclonal antibodies specific for the de-N-acetylated forms, but the isolation and chemical characterization of such compounds have not yet been performed. Since indirect evidence suggested that de-N-acetylGD3 ganglioside could be present in human melanoma tumors, we analyzed the gangliosides purified from a 500-g pool of those tumors. The de-N-acetylGD3 that was found to migrate just below GD2 in thin-layer chromatography was isolated from the disialogangliosides by high-pressure liquid chromatography using the specific antibody SGR37 to monitor the elution. The amount of antigen was found to be 320 ng per gram of fresh tumor or 0.1% of total gangliosides. Gas chromatography-mass spectrometry analysis of the antibody-positive ganglioside showed that sialic acids were formed of one molecule of N-acetylneuraminic acid and one molecule of neuraminic acid. Radioactive re-N-acetylation of the antigen yielded a GD3-like ganglioside with the radioactive label on the external sialic acid. The constitutive fatty acids were found to differ markedly from those of GD3 and 9-O-acetylGD3 isolated from the same pool of tumors. The major fatty acids were C16:0 and C18:0 in de-N-acetylGD3, whereas GD3 and its 9-O-acetylated derivative contained a large amount of C24:1. These data show that de-N-acetylGD3 ganglioside is indeed present in human melanoma tumors, and the fatty acid content suggests the existence of a de-N-acetylase mostly active on the molecular species of gangliosides with short-chain fatty acids.
Popa
Iuliana
I
Laboratory of Dermatological Research, University of Lyon-1 and Edouard Herriot Hospital, 69437 Lyon Cx 03, France.
Pons
Alexandre
A
Mariller
Christophe
C
Tai
Tadashi
T
Zanetta
Jean-Pierre
JP
Thomas
Luc
L
Portoukalian
Jacques
J
D000107:Acetylation; D002236:Carbohydrate Conformation; D005732:Gangliosides / Q000737:chemistry* / Q000302:isolation & purification*; D006801:Humans; D007150:Immunohistochemistry; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D008958:Models, Molecular; D019158:N-Acetylneuraminic Acid / Q000302:isolation & purification
D005732:Gangliosides; C026226:ganglioside, GD3; D019158:N-Acetylneuraminic Acid