Synthetic GM1 improves motor and memory dysfunctions in mice with monoallelic or biallelic disruption of GM3 synthase.

This study attempts to answer the question of whether mice with biallelic and monoallelic disruption of the St3gal5 (GM3 synthase) gene might benefit from GM1 replacement therapy. The GM3 produced by this sialyltransferase gives rise to downstream GD3 and the ganglio-series of gangliosides. The latter includes the a-series (GM1 + GD1a), which has proved most essential for neuron survival and function (especially GM1, for which GD1a provides a reserve pool).

Mice deficient in GM1 manifest both motor and non-motor symptoms of Parkinson's disease; successful treatment with synthetic GM1 ganglioside.

Parkinson's disease (PD) is a major neurodegenerative disorder characterized by a variety of non-motor symptoms in addition to the well-recognized motor dysfunctions that have commanded primary interest. We previously described a new PD mouse model based on heterozygous disruption of the B4galnt1 gene leading to partial deficiency of the GM1 family of gangliosides that manifested several nigrostriatal neuropathological features of PD as well as movement impairment. We now show this mouse also suffers three non-motor symptoms characteristic of PD involving the gastrointestinal, sympathetic cardiac, and cerebral cognitive systems.

A Bacterial Expression Platform for Production of Therapeutic Proteins Containing Human-like O-Linked Glycans.

We have developed an Escherichia coli strain for the in vivo production of O-glycosylated proteins. This was achieved using a dual plasmid approach: one encoding a therapeutic protein target, and a second encoding the enzymatic machinery required for O-glycosylation. The latter plasmid encodes human polypeptide N-acetylgalactosaminyl transferase as well as a β1,3-galactosyl transferase and UDP-Glc(NAc)-4-epimerase, both from Campylobacter jejuni, and a disulfide bond isomerase of bacterial or human origin.

Pharmacological Effects on Ceroid Lipofuscin and Neuronal Structure in Cln3 Mouse Brain Cultures.

Juvenile Batten disease (JBD) is an inherited disorder that is characterized by the development of blindness, seizures, and progressive motor, psychiatric, and cognitive impairment. A model of JBD expressing the predominant human mutation (Cln3 ) has been explored. Dissociated brain cultures from Cln3 knock-in mice were compared to wild type (WT) for effects on granules of ceroid lipofuscin (CL) and neuronal structure.

ST6GalNAc-I controls expression of sialyl-Tn antigen in gastrointestinal tissues.

Sialyl-Tn is a simple mucin-type carbohydrate antigen aberrantly expressed in gastrointestinal adenocarcinomas and in the precursor lesion intestinal metaplasia. Sialyl-Tn tumour expression is an independent indicator of poor prognosis. We have previously shown in vitro that ST6GalNAc-I and ST6GalNAc-II sialyltransferases can synthesize sialyl-Tn.

Structural insight into mammalian sialyltransferases.

Mammalian cell surfaces are modified by complex arrays of glycoproteins, glycolipids and polysaccharides, many of which terminate in sialic acid and have central roles in essential processes including cell recognition, adhesion and immunogenicity. Sialylation of glycoconjugates is performed by a set of sequence-related enzymes known as sialyltransferases (STs). Here we present the crystal structure of a mammalian ST, porcine ST3Gal-I, providing a structural basis for understanding the mechanism and specificity of these enzymes and for the design of selective inhibitors.

Expression of active human sialyltransferase ST6GalNAcI in Escherichia coli.

Background: The presence of terminal, surface-exposed sialic acid moieties can greatly enhance the in vivo half-life of glycosylated biopharmaceuticals and improve their therapeutic efficacy. Complete and homogeneous sialylation of glycoproteins can be efficiently performed enzymically in vitro but this process requires large amounts of catalytically active sialyltransferases. Furthermore, standard microbial hosts used for large-scale production of recombinant enzymes can only produce small quantities of glycosyltransferases of animal origin, which lack catalytic activity.

Variants of the beta 1,3-galactosyltransferase CgtB from the bacterium Campylobacter jejuni have distinct acceptor specificities.

The gene clusters encoding the lipooligosaccharide biosynthesis glycosyltransferases from Campylobacter jejuni have previously been divided in eight classes based on their genetic organization. Here, three variants of the beta1,3-galactosyltransferase CgtB from two classes were purified as fusions with the maltose-binding protein (MalE) from Escherichia coli and their acceptor preference was determined. The acceptor preference of each CgtB variant was directly related to the presence or absence of sialic acid in the acceptor, which correlated with the core oligosaccharide structure in vivo.

GlycoPEGylation of recombinant therapeutic proteins produced in Escherichia coli.

Covalent attachment of polyethylene glycol, PEGylation, has been shown to prolong the half-life and enhance the pharmacodynamics of therapeutic proteins. Current methods for PEGylation, which rely on chemical conjugation through reactive groups on amino acids, often generate isoforms in which PEG is attached at sites that interfere with bioactivity. Here, we present a novel strategy for site-directed PEGylation using glycosyltransferases to attach PEG to O-glycans.

Glycosynthase-mediated synthesis of glycosphingolipids.

Glycosphingolipids play crucial roles in virtually every stage of the cell cycle, and their clinical administration has been proposed as a treatment for Alzheimer's, Parkinson's, stroke, and a range of other conditions. However, lack of supply has severely hindered testing of this potential. A novel glycosynthase-based synthetic strategy is demonstrated, involving a mutant of an endoglycoceramidase in which the catalytic nucleophile has been ablated.