Expression and regulation of sialic acid biosynthesis and sialyltransferase genes in the mammary gland

Jovana Maksimovic
Sialic acids are a family of nine-carbon, acidic monosaccharides. In mammals, they are typically located at the non-reducing terminus of oligosaccharide chains, connected either via an α2,3- or α2,6- linkage. Sialic acids can also form α2,8-linked poly-sialic acid chains on gangliosides and glycoproteins. Milk sialylglycoconjugates can protect the gastrointestinal tract of the suckling neonate by competitively binding to invading pathogens and promoting growth of beneficial flora, and their
more » ... ntial role in post-natal brain development is of particular interest in human infant nutrition. Although the concentration and distribution of sialylglycoconjugates has been extensively studied in the milk of various species, the regulation of sialylation in the mammary gland, in the context of lactation, has been limited. Sialic acid can be synthesised in all tissues to satisfy local sialylation requirements, although the final complement of sialylated structures is determined by the sialyltransferase enzymes. Sialyltransferases are a family of Golgi membrane-bound, glycosyltransferases that transfer sialic acid from CMP-sialic acid to carbohydrate acceptor groups of glycoproteins, glycolipids and free oligosaccharides, forming various sialylglycoconjugates. Their expression is primarily controlled at the level of transcription and is expedited through the use of several tissue and development-specific promoters, giving rise to numerous transcripts divergent only in their 5' untranslated regions. Thus far, 20 mammalian sialyltransferases have been cloned. Depending on the type of linkage formed and the type of sugar acceptor, they are segregated into four groups: ST6Gal, ST6GalNAc, ST3Gal and ST8Sia. This study describes the expression of sialic acid biosynthesis and sialyltransferase genes in the lactating eutherian and marsupial mammary gland and the role of lactogenic hormones in their regulation. It also examines the developmental context in which milk iv sialylglycoconjugates may be important. Analysis of mouse mamma [...]
doi:10.4225/03/58901c6014743 fatcat:nclaz6hmp5hihgxfcz56txalba