ST3Gal II and beta4GalNacT-I are S-acylated at N-terminal cysteines involved in homo-dimerization

SABRNA CHUMPEN RAMIREZ; FERNANDO RUGGIERO; JOSE LUIS DANIOTTI; JAVIER VALDEZ TAUBAS

Córdoba

Congreso; LII Reunión Anual de SAIB; 2016

SAIB

ST3Gal II and BETA 4GalNacT-I are S-acylated at N-terminal cysteines involved in homo-dimerizationSabrina Chumpen Ramirez, Fernando M. Ruggiero, José L. Daniotti and Javier Valdez Taubas Depto. Química. Biológica., CIQUIBIC-CONICET, Fac. Cs. Químicas, Univ. Nac. de CórdobaGanglioside glycosyltransferases (GGTs) are type-II membrane proteins that consist in a short N-terminal cytoplasmic tail, a transmembrane domain (TMD), and a luminally oriented C-terminal domain that bears the catalytic domain. We have previously shown that the N-terminal domain (Ntd) of the GGTs ST3Gal V, ST8Sia I and 4GalNacT I are S-acylated at conserved cysteine residues when expressed in CHO-K1 cells. Here, we extended our studies to ST3Gal II, a GT that sialylates glycolipids and glycoproteins, and found that full length ST3Gal II is also S-acylated. S-acylation, commonly known as palmitoylation, is catalyzed by a family of palmitoyltransferases (PATs) that are mostly localized at the Golgi complex but also at the ER and the plasma membrane. Using GT?s ER-retention mutants, we found that S-acylation of 4GalNT I and ST3Gal II takes place at different compartments, suggesting that 4GalNT I and ST3Gal II are not substrates of the same PAT and this may be due to the different localization of the conserved cysteines in these GTs (TMD or cytosolic tail, respectively). We also found that cysteines that are target of S-acylation on Beta 4GalNacT I and ST3Gal II are involved in the formation of homodimers through disulfide bonds. We show an increase of ST3Gal II dimmers in the presence of the PAT inhibitor 2-bromopalmitate, suggesting that S-acylation may be regulating GTs homo-dimerization