Glycobiology, Vol 8, 481-487, Copyright © 1998 by Society for Glycobiology
B Vanhove, F Sebille, A Cassard, B Charreau and JP Soulillou
Gal alpha 1,3Gal carbohydrate residues are present in the glycoproteins and
glycolipids of lower mammals, and appear to be involved in the binding
specificity of several membrane receptors. We report here that endothelial
cells stimulated with lipopolysaccharide or inflammatory cytokines modulate
their expression of UPD-Gal: beta-D-Gal alpha 1,3- galactosyltransferase
(alpha 1,3GT), the Golgi enzyme that attaches a galactose in alpha 1,3
configuration to an N-acetyllactosamine acceptor. Upon activation, the
steady state level of mRNA is transiently increased, the modifications
being paralleled by a transcriptional regulation of the gene.
Cell-associated enzyme activity, on the other hand, falls rapidly after
activation, before being up- and downregulated with kinetics that parallel
those of the mRNA, and after 3 days reaches a level representing 40-60% of
the activity in cells before activation. Overall Gal alpha 1,3Gal
expression at the cell surface follows enzyme activity, except that it is
insensitive to the rapid and transient reduction of activity occurring
shortly after activation. This reduced alpha 1,3GT activity in stimulated
EC is correlated with lower stability of the protein, and with a switch in
the expression of the isoform pattern, isoform 1 being predominant in
resting cells whereas after activation it is isoform 2 that predominates.
The two isoforms, however, appear to have similar intrinsic stability, so
that the reduced stability of the enzyme in activated EC probably results
from an induced proteolytic degradation pathway.
ORIGINAL ARTICLES
Transcriptional and posttranscriptional regulation of alpha 1,3- galactosyltransferase in activated endothelial cells results in decreased expression of Gal alpha 1,3Gal
INSERM, Institut National de la Sante et de la Recherche Medicale, Xenotransplantations, Nantes, France.
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