CHINESE-HAMSTER OVARY CELLS LACKING GM1 AND GD1A SYNTHESIZE GANGLIOSIDES UPON TRANSFECTION WITH HUMAN GM2 SYNTHASE

GM3-positive Chinese hamster ovary cells (CHO-K cells) lack the abilit y to synthesize GM2 and the complex gangliosides GM1 and GD1a from [H- 3]Gal added to the culture medium. However, they acquire the ability t o synthesize GM2 and to synthesize and immunoexpress complex gangliosi des upon transient transfection with a cDNA encoding the human GM3:N-a cetylgalactosaminyl transferase (GM2 synthase). The activities of endo genous GM1- and GD1a-synthases in the parental cell line and in cells transfected with the plasmid with or without the GM2 synthase cDNA wer e essentially identical and comparable in terms of specific activity w ith the endogenous GM3 synthase. Results indicate that glycosyltransfe rases acting on GM2 to produce GM1 and GD1a are constitutively present in CHO-K1 cells, and that the expression of their activities depend o n the supply of the acceptor GM2. In addition, these results lend supp ort to the notion that GM2 synthase is a key regulatory enzyme influen cing the balance between simple and complex gangliosides. (C) 1997 Els evier Science B.V.