Poly-N-acetyllactosamine alterations of Thy-1 glycoprotein in lymphocyte differentiation.
Developmental changes in murine lymphocyte Thy-1 include both quantitative and qualitative alterations involving N-linked oligosaccharides. Comparison of immature with mature T-cells has shown that the oligosaccharides of Thy-1 are characterized by an increase in the number of sialic acid residues responsible for the acidic pI of peripheral T-cell Thy-1, and a decrease in those oligosaccharides responsible for Mr heterogeneity of thymocyte Thy-1. The research reported here suggests that the basis of the large Mr heterogeneity in Thy-1 of immature T-cells is the presence of repeating N-acetyllactosamine (R'Gal beta 1,4GlcNAc beta 1,3R") units in the oligosaccharide portion of the molecule. Lymphocytes were surface iodinated and 125I-thy-1 was purified by immunoprecipitation and preparative nonequilibrium pH gradient electrophoresis. The minimal Mr of unglycosylated Thy-1 after endoglycosidase F digestion was 15,000-16,000. Digestion of Thy-1 with endo-beta-galactosidase suggested that the complex type N-linked glycans in thymocytes, but not in lymph node T-cells, contained increased levels of polylactosamine. The presence of polylactosamine was confirmed by binding to a Datura stramonium lectin column which retarded and bound approx. 50% of thymocyte Thy-1 and only about 18% of lymph node T-cell Thy-1. Affinity chromatography using anti-i antibody immobilized on agarose beads indicated that the polylactosamine is probably present in a predominantly linear form. Since alterations of polylactosamine structures have been implicated in development and transformation in several systems, the present results suggest an important role for these glycans in immune-cell differentiation.
Morrison
M H
MH
Lynch
R A
RA
Esselman
W J
WJ
D000818:Animals; D000954:Antigens, Surface / Q000302:isolation & purification; D002454:Cell Differentiation; D002846:Chromatography, Affinity; D004586:Electrophoresis; D006023:Glycoproteins / Q000032:analysis*; D006026:Glycoside Hydrolases; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D051379:Mice; D008809:Mice, Inbred C3H; D011134:Polysaccharides / Q000032:analysis*; D013601:T-Lymphocytes / Q000032:analysis / Q000166:cytology* / Q000276:immunology; D018800:Thy-1 Antigens
D000954:Antigens, Surface; D006023:Glycoproteins; D011134:Polysaccharides; D018800:Thy-1 Antigens; C037199:poly-N-acetyllactosamine; D006026:Glycoside Hydrolases; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase