An activation-associated ganglioside in rat thymocytes.

During the activation of rat thymocytes elicited by stimulation with 12-O-tetradecanoylphorbol-13-acetate (TPA) and calcium ionophore A23187, the total amount of gangliosides per cell was demonstrated to increase, reaching a maximum level several times higher than that of resting cells at 48 h after activation when measured at 24-h intervals. The amount of the overwhelmingly predominant ganglioside in resting thymocytes, GD1c (NeuGc,NeuGc) (Nohara, K., Suzuki, M., Inagaki, F., and Kaya, K. (1991) J. Biochem. (Tokyo) 110, 274-278), was found to increase further as a result of activation. Furthermore, another ganglioside, which was barely recognizable in resting thymocytes, was found to increase in activated and proliferating thymocytes to a level similar to that of GD1c. This activation-associated ganglioside was isolated and its structure examined. On the basis of the results of compositional analysis, methylation analysis, sialidase hydrolysis followed by detection with cholera toxin B subunit on TLC, and proton NMR spectroscopy, this ganglioside was clarified to be a rare species of GD1b containing two N-glycolylneuraminic acid residues. On the other hand, when the thymocytes were activated using concanavalin A (ConA) as a stimulant, the amount of gangliosides per cell was increased more strikingly than that in thymocytes activated with TPA and A23187. In the ConA-activated thymocytes, many other gangliosides, in addition to GD1c and GD1b-(NeuGc,NeuGc), were demonstrated to appear in large amounts. The cause of this difference in gangliosides between thymocytes activated with a combination of TPA and A23187 and those activated with ConA is also discussed.