Differential O-glycosylation in cortical and medullary thymocytes.
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 beta1,3GalNAc1,0 Ser/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 two-fold 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.
Alvarez
Georgina
G
Laboratorio de Inmunología, Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, P.O. Box 70159, 04510, Mexico.
Lascurain
Ricardo
R
Hernández-Cruz
Pedro
P
Tetaert
Daniel
D
Degand
Pierre
P
Gorocica
Patricia
P
Espinosa
Blanca
B
Zenteno
Edgar
E
Chávez
Raúl
R
D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D019075:Electrophoresis, Capillary; D006031:Glycosylation; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D008861:Microsomes / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D003907:Dexamethasone