Expression of sialyltransferases increases the activity of other Golgi resident glycosyltransferases

SPESSOT WALDO A; CRESPO PILAR M.; DANIOTTI JOSÉ L; MACCIONI HUGO JF

Mar del Plata, Buenos Aires

Congreso; XLIII Reunión Nacional de la Sociedad Argentina de Investigación en Bioquímica y Biología Celular (SAIB); 2007

The activity of the endogenous galactosyltransferase 1 (GalT1) and sialyltransferase 1 (Sial T1) of CHO-K1 cells were increased 1.4 and 2.3 fold, respectively, in a cell clone (ST18) stably expressing sialyltransferase 2 (SialT2). Here we show, by biochemical assays, that this activation was neither due to the appareance of activators (i.e. glycolipid products) nor to evident stabilization of GalT1 and SialT1. Real-time PCR experiments failed to demonstrate transcriptional activation of GalT1 and SialT1 genes. Since SialT2 forms a complex with GalT1 and Sialt1 with participation of their N-terminal domains (Ntd), we looked for the activation of GalT1 and SialT1 in a cell clone that stably express the NtD of SialT2 fused to the GFP. Results showed a poor activity of the Ntd of SialT2 to activate GalT1 and SialT1. Taken together, these results indicate that activation of GalT1 and SialT1 by SialT2 is associated to its lumenal domain, and reinforce the possibility previously advanced of an effect on the topological organization of these enzymes along the Golgi complex (Uliana et al., 2006).