Regioisomeric SCFA attachment to hexosamines separates metabolic flux from cytotoxicity and MUC1 suppression.

Chemical biology studies, exemplified by metabolic glycoengineering experiments that employ short chain fatty acid (SCFA)-hexosamine monosaccharide hybrid molecules, often suffer from off-target effects. Here we demonstrate that systematic structure-activity relationship (SAR) studies can deconvolute multiple biological activities of SCFA-hexosamine analogues by demonstrating that triacylated monosaccharides, including both n-butyrate- and acetate-modified ManNAc analogues, had dramatically different activities depending on whether the free hydroxyl group was at the C1 or C6 position. The C1-OH (hemiacetal) analogues enhanced growth inhibition in MDA-MB-231 human breast cancer cells and suppressed expression of MUC1, which are attractive properties for an anticancer agent. By contrast, C6-OH analogues supported high metabolic flux into the sialic acid pathway with negligible growth inhibition or toxicity, which are desirable properties for glycan labeling in healthy cells. Importantly, these SAR were general, applying to other hexosamines ( e.g., GlcNAc) and non-natural sugar "scaffolds" ( e.g., ManNLev). From a practical standpoint, the ability to separate toxicity from flux will facilitate the use of MOE analogues for cancer treatment and glycomics applications, respectively. Mechanistically, these findings overturn the premise that the bioactivities of SCFA-monosaccharide hybrid molecules result from their hydrolysis products ( e.g., n-butyrate, which acts as a histone deacetylase inhibitor, and ManNAc, which activates sialic acid biosynthesis); instead the SAR establish that inherent properties of partially acylated hexosamines supersede the cellular responses supported by either the acyl or monosaccharide moieties.

Gangliogenesis in the enteric nervous system: roles of the polysialylation of the neural cell adhesion molecule and its regulation by bone morphogenetic protein-4.

The neural crest-derived cells that colonize the fetal bowel become patterned into two ganglionated plexuses. The hypothesis that bone morphogenetic proteins (BMPs) promote ganglionation by regulating neural cell adhesion molecule (NCAM) polysialylation was tested. Transcripts encoding the sialyltransferases, ST8Sia IV (PST) and ST8Sia II (STX), which polysialylate NCAM, were detectable in fetal rat gut by E12 but were downregulated postnatally. PSA-NCAM-immunoreactive neuron numbers, but not those of NCAM, were developmentally regulated similarly. Circular smooth muscle was transiently (E16-20) PSA-NCAM-immunoreactive when it is traversed by migrating precursors of submucosal neurons. Neurons developing in vitro from crest-derived cells immunoselected at E12 with antibodies to p75(NTR) expressed NCAM and PSA-NCAM. BMP-4 promoted neuronal NCAM polysialylation and clustering. N-butanoylmannosamine, which blocks NCAM polysialylation, but not N-propanoylmannosamine, which does not, interfered with BMP-4-induced neuronal clustering. Observations suggest that BMP signaling enhances NCAM polysialylation, which allows precursors to migrate and form ganglionic aggregates during the remodeling of the developing ENS.