Lectin domains as scaffold to direct O-GalNAc glycan biosynthesis

LORENZ, VIRGINIA; CEJAS, RB; IRAZOQUI FJ

Mar del Plata, Argentina

Congreso; SAIB 2015; 2015

Sociedad Argentina de Investigaciones Bioquímicas (SAIB)

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