Expression of galectin 4 in the rat small intestine during postnatal development.

We determined the expression of an endogenous lectin, galectin 4, in the rat small intestine during postnatal development. The mRNA levels of galectin 4 did not change significantly between birth and adulthood. In contrast, the protein was present at higher levels after than before weaning, and the potential ligands for galectin 4 were more highly represented in the enterocyte microvilli of weaned than of suckling rats.

Expression and localization of galectin 4 in rat stomach during postnatal development.

Galectins are lectins implicated in cell-cell or cell-matrix adhesion, cell growth, the cell cycle, transcription processes, and apoptosis, and some of them are differentially regulated during pre- or post-natal development. The purpose of the present study was to determine whether the expression of galectin 4 is relevant to developmental processes during postnatal development in the rat stomach. Galectin 4 expression in the rat gastric mucosa, between birth and adulthood, was studied at the protein and mRNA levels by western and northern blotting, respectively.

Regulation of the intestinal glycoprotein glycosylation during postnatal development: role of hormonal and nutritional factors.

This review focuses on the regulation of the glycoprotein glycosylation process in small intestine and colon during postnatal development. Glycoproteins play a prominent part in intestine as mucins secreted by the goblet cells and as molecules of biological interest largely present in the microvillus membrane of the enterocytes (digestive enzymes, transporters). The age-related changes in the intestinal glycosylation control the quality of glycan chains of glycoproteins.

Glucocorticoid-induced maturation of glycoprotein galactosylation and fucosylation processes in the rat small intestine.

We determined the role of glucocorticoids in the maturation of glycoprotein galactosylation and fucosylation processes in the rat small intestine during postnatal development. Treatment of suckling rats with hydrocortisone (HC) increased activities of an O-glycan: galactosyltransferase, and of an alpha-1,2-fucosyltransferase, through transcriptional regulation of the FTB gene. The activities of a fucosyltransferase inhibitor and of the enzymes responsible for the synthesis and degradation of GDP-fucose were unaffected by the treatment, whereas a fall in the activity of alpha-L-fucosidase was observed.

The mitochondria-associated endoplasmic-reticulum subcompartment (MAM fraction) of rat liver contains highly active sphingolipid-specific glycosyltransferases.

Although most glycosphingolipids (GSLs) are thought to be located in the outer leaflet of the plasma membrane, recent evidence indicates that GSLs and their precursor, ceramide, are also associated with intracellular organelles and, particularly, mitochondria. GSL biosynthesis starts with the formation of ceramide in the endoplasmic reticulum (ER), which is transported by controversial mechanisms to the Golgi apparatus, where stepwise addition of monosaccharides on to ceramides takes place. We now report the presence of GSL-biosynthetic enzymes in a subcompartment of the ER previously characterized and termed 'mitochondria-associated membrane' (MAM).

Increasing endogenous ceramide using inhibitors of sphingolipid metabolism maximizes ionizing radiation-induced mitochondrial injury and apoptotic cell killing.

To enhance the killing effects of ionizing radiation, we amplified the endogenous ceramide signal in Jurkat cell cultures using 3 different inhibitors of sphingolipid metabolism: DL-PDMP, D-MAPP and imipramine. Of the various possible drug combinations, only DL-PDMP (20 microM) + imipramine (20 microM) and DL-PDMP (20 microM) + imipramine (20 microM) + D-MAPP (5 microM) induced a major increase in ceramide levels, reaching 240% and 340% of control values, respectively, after incubation for 48 hr. With these models, we demonstrate that endogenously formed ceramide triggers time- and concentration-dependent apoptosis through induction of mitochondrial injury and activation of the caspase pathway.

Polyamine participation in the maturation of glycoprotein fucosylation, but not sialylation, in rat small intestine.

The aim of this study was to determine the role of polyamines in the diet-related maturation of the intestinal glycoprotein glycosylation during postnatal development in the rat. The activity of alpha-2,6-sialyltransferase and the sialylated forms of glycoproteins in the intestinal brush-border membranes were found to decrease considerably after weaning, in parallel with the intestinal level of putrescine. By contrast, the activity of alpha-1,2-fucosyltransferases, the mRNA levels for two alpha-1,2-fucosyltransferase genes, FTA and FTB, and the fucosylated forms of glycoproteins all increased after weaning, in parallel with the levels of spermidine and spermine.

Proteomics analysis of cellular response to oxidative stress. Evidence for in vivo overoxidation of peroxiredoxins at their active site.

The proteomics analysis reported here shows that a major cellular response to oxidative stress is the modification of several peroxiredoxins. An acidic form of the peroxiredoxins appeared to be systematically increased under oxidative stress conditions. Peroxiredoxins are enzymes catalyzing the destruction of peroxides.