S-Acylation of Glycolipid-Glycosyltransferases

CHUMPÉN, S; VALDEZ TAUBAS J

Rosario

Congreso; 50 SAIB; 2014

Sociedad Argentina de Investogación en Buiquímica y Biol. Molecular

S-acylation of Glycolipid-Glycosyltransferases Glycosyltransferases (GTs) catalyze the glycosylation of proteins and lipids in the Golgi complex. These are type II transmembrane proteins, with a short N-terminal cytoplasmic domain, a transmembrane domain (TMD), and a catalytic region oriented to the lumen. Sequence analyses revealed the presence of conserved cysteine residues at the cytosolic border of- or within the- transmembrane domain. Cysteines in similar positions are known to be S-acylated (or palmitoylated) in SNAREs and viral fusion proteins but, to date, the lipid modification of mammalian GTs has not been described. Our experiments reveal that the N-Terminal regions of Ganglioside-GTs, SialT1, SialT2 and GalNAcT can be S-acylated in CHO-K1 and HEK293F cells. S-acylation in mammals is mediated by a family of Palmitoyltransferases (PATs), which localize mostly to the Golgi, however, two members of this family, DHHC4 and DHHC6, localize to the ER. Using a GalNacT ER-retention mutant we found that GTs palmitoylation takes place within this organelle, suggesting that these are candidate PATs for GTs. Results suggest that DHHC4 but not DHHC6 is involved in GalNacT and SialT2 S-acylation. Additionally, we found that GTs form DTT-sensitive multimers, mediated by disulfide links between the cysteines that could be target for S-acylation, indicating that GTs palmitoylation could be regulating GTs multimer formation