Endothelial alpha 2,6-linked sialic acid inhibits VCAM-1-dependent adhesion under flow conditions.
We have previously shown that costimulation of endothelial cells with IL-1 + IL-4 markedly inhibits VCAM-1-dependent adhesion under flow conditions. We hypothesized that sialic acids on the costimulated cell surfaces may contribute to the inhibition. Northern blot analyses showed that Gal beta 1-4GlcNAc alpha 2, 6-sialyltransferase (ST6N) mRNA was up-regulated in cultured HUVEC by IL-1 or IL-4 alone, but that the expression was enhanced by costimulation, whereas the level of Gal beta 1-4GlcNAc/Gal beta 1-3GalNAc alpha2,3-sialyltransferase (ST3ON) mRNA was unchanged. Removing both alpha 2,6- and alpha 2,3-linked sialic acids from IL-1 + IL-4-costimulated HUVEC by sialidase significantly increased VCAM-1-dependent adhesion, whereas removing alpha 2,3-linked sialic acid alone had no effect; adenovirus-mediated overexpression of ST6N with costimulation almost abolished the adhesion, which was reversible by sialidase. The same treatments of IL-1-stimulated HUVEC had no effect. Lectin blotting showed that VCAM-1 is decorated with alpha 2,6- but not alpha 2,3-linked sialic acids. However, overexpression of alpha 2,6-sialyltransferase did not increase alpha 2,6-linked sialic acid on VCAM-1 but did increase alpha 2,6-linked sialic acids on other proteins that remain to be identified. These results suggest that alpha 2,6-linked sialic acids on a molecule(s) inducible by costimulation with IL-1 + IL-4 but not IL-1 alone down-regulates VCAM-1-dependent adhesion under flow conditions.
Abe
Y
Y
Speros Martel Section of Leukocyte Biology, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
Smith
C W
CW
Katkin
J P
JP
Thurmon
L M
LM
Xu
X
X
Mendoza
L H
LH
Ballantyne
C M
CM
D000256:Adenoviridae / Q000235:genetics; D001665:Binding Sites / Q000276:immunology; D001783:Blood Flow Velocity; D002236:Carbohydrate Conformation; D002448:Cell Adhesion / Q000276:immunology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D005822:Genetic Vectors; D006801:Humans; D015151:Immunoblotting; D037102:Lectins / Q000378:metabolism; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000096:biosynthesis; D012212:Rheology; D012794:Sialic Acids / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D012799:Sialyltransferases / Q000096:biosynthesis / Q000235:genetics; D014407:Tumor Cells, Cultured; D014471:Umbilical Veins; D019010:Vascular Cell Adhesion Molecule-1 / Q000502:physiology*; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase
D037102:Lectins; D012333:RNA, Messenger; D012794:Sialic Acids; D019010:Vascular Cell Adhesion Molecule-1; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase