Regulation of N-glycolylneuraminic acid biosynthesis in developing pig small intestine

Abstract

N -Glycolylneuraminic acid (Neu5Gc), an abundant sialic acid in animal glycoconjugates, is formed by the enzyme CMP-N-acetylneuraminic acid (CMP-Neu5Ac) hydroxylase. The amount of Neu5Gc relative to other sialic acids is highly dependent on the species, tissue and developmental stage. Although the activity of the hydroxylase is a key factor in controlling Neu5Gc incorporation in adult animals, little is known about the regulation of hydroxylase expression and the role of this enzyme in determining changes in Neu5Gc during development. Using pig small intestine as a model system, the appearance of total sialic acid and the regulation of Neu5Gc biosynthesis during development were studied in various regions of this tissue. The amount of total sialic acid and Neu5Gc declined markedly in 2 weeks after birth. Although in subsequent developmental phases there were no positional differences in total sialic acid, a significant proximal-to-distal increase in Neu5Gc was detected. In all cases, a good correlation between the amount of Neu5Gc, the activity of the hydroxylase and the level of hydroxylase mRNA was observed. However, Western-blot analysis revealed considerable accumulation of less active enzyme in the post partum period, which persisted until adulthood. No evidence for cytosolic factors influencing the hydroxylase activity or for the formation of truncated enzyme was found, raising the possibility that other regulatory mechanisms are involved. The relevance of these results in the formation of Neu5Gc as a receptor for certain pig enteric pathogens is also discussed.

Housekeeping promoter 5’pcmah-2 of pig CMP-N-acetylneuraminic acid hydroxylase gene for NeuGc expression

“…Several studies have provided direct or indirect evidence that NeuGc expression is tissue-and age-dependent, and may also be influenced by cell activation and disease status [12,14,15]. In mouse and human, the CMAH mRNA expression has been reported to be regulated during LPS-stimulated mouse B-cell activation and in human stem cells, as observed by RT-PCR [13,18].…”

“…Although the precise transcriptional approaches were presently not made due to its limited information on cis-and trans-elements related to CMAH gene regulation in mouse and human, the mechanism of transcriptional regulation will be interesting in terms of tissue-specific and environmentresponsive expression. In case of pig, the level of CMAH mRNA in the developing jejunum has been correlated with variations in the enzyme activity correlating with the age and positional susceptibility for an enteric disease [15]. Although the transcriptional regulation is fundamentally interested in the relationship between the CMAH mRNA expression and biological phenomena, no any promoter studies were made to date, even in the pcmah promoter.…”

“…Furthermore, the appearance of NeuGc is influenced by various endotoxins and intestinal parasites, in particular, lipopolysaccharide (LPS)-induced mouse B-cell activation, reduces CMAH mRNA expression [12][13][14]. Moreover, the regulation of NeuGc biosynthesis in developing pig small intestine is directly correlated with hydroxylase activity and CMAH mRNA expression [15]. Although these reports indicate that cmah expression is generally regulated by developmental process and infectious conditions, the molecular mechanism(s) for regulation of cmah, directly related to NeuGc biosynthesis, remains unknown in all organisms.…”

Three Main Inducers of Alphacoronavirus Infection of Enterocytes: Sialic Acid, Proteases, and Low pH

“…Binding to pAPN and sialic acid are two independent processes. Interestingly, binding to pAPN is more efficient in the absence of sialic acid [40].…”

“…3. Ribbon drawing of the TGEV PL1pro [40]. The entire structure resembles a hand, with the palm, thumb, and fingers represented in yellow, green, and blue, respectively.…”