Lectin domains as scaffold to direct O-GalNAc glycan biosynthesis.

VIRGINIA LORENZ; ROMINA B CEJAS; FERNANDO J. IRAZOQUI

Mar del Plata

Congreso; 51 Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2015

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

O-GalNAc glycan biosynthesis occurs mainly in Golgi. Molecular organization and functional regulation of thisprocess are not well understood. We evaluated the effect of lectin domains (β-trefoil fold) of polypeptide GalNActransferases(ppGalNAc-Ts) on catalytic activity of glycosyltransferases involved in the first steps of O-GalNAcglycosylation. The presence of lectin domain of ppGalNAc-T3 (T3lec) or -T4 (T4lec) during ppGalNAc-T2 andppGalNAc-T3 catalytic reaction had a clear inhibitory effect on GalNAc-T activity. In transient transfected CHOldlD cells a catalytically inactive mutant, mimicking a lectin domain, reduced αGalNAc incorporation in relation to amock vector. Also, both lectin domains interacted with the catalytic domain of ppGalNAc-T2 and this interaction wasnot mediated by carbohydrate. Opposite to the previous results, T3lec but not T2lec and T4lec, had a clear activatingeffect of core 1 galactosyltransferase (C1GalT) enzyme activity. We also see an enhancing effect on C1GalT activityin presence of full-length ppGalNAc-T3. We describe for the first time a role for lectin domains that involvedprotein-protein interaction in the regulation of glycosyltransferases activity of O-glycan biosynthesis pathway