Differential O-glycosylation in cortical and medullary thymocytes

摘要

Differentiation of T lymphocytes is characterized by variable expression of CD8/CD4 co-receptor molecules and changes in the glycosylation pattern. In this work, O-glycosylation was analyzed in microsomes from murine thymocytes purified with the PNA and Amaranthus leucocarpus (ALL) lectins, specific for the T antigen (Gal beta 1,3GalNAc1,0Ser/Thr) in cortical and medullary thymocytes, respectively. Three peptides were used as acceptors for UDP-N-acetylgalactosamine: polypeptide N-acetylgalactosaminyl-transferase (GalNAc transferase)- the peptide motif TTSAPTTS was the best glycosylated one. Cortical ALL-PNA+ thymocytes showed two-fold higher GalNAc transferase activity than ALL+PNA- thymocytes: however. capillary electrophoresis showed a higher proportion of di-versus mono-glycosylated peptides for ALL+PNA- than for ALL+PNA+. We compared the GalNAc transferase activity of thymocytes from dexamethasone-treated mice versus control mice. GalNAc transferase activity was six-fold higher in thymocytes from control mice than from dexamethasone-treated mice: the rate of di-glycosylated peptides for dexamethosone-resistant ALL+ was twofold higher than for ALL- thymocytes. Our results confirm an upregulated biosynthesis of O-glycosidically linked glycans on T cell surface glycoproteins, and suggest that the modification of GalNAc transferase activity plays a relevant role during the maturation process of thymic cells. (c) 2006 Elsevier B.V. All rights reserved.