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Development of carbohydrate array technology to systematically explore the functional role of glycans in healthy and diseased states

Final Report Summary - EUROGLYCOARRAYS (Development of carbohydrate array technology to systematically explore the functional role of glycans in healthy and diseased states)

Carbohydrates are components of all living cells as part of the glycoconjugates such as glycolipids, glycoproteins and proteoglycans. Every cell has a glycocalyx, a layer of carbohydrates that are involved in intercellular communication and are receptors for carbohydrate binding proteins. The science of ‘glycomics’ tries to understand these protein carbohydrate interactions in the same way in which proteomics maps protein-protein interactions. A major difference between these two disciplines is that carbohydrate sequence and structure is not directly encoded in the genome and hence genetic studies in glycomics give only limited information. The key tools that have emerged in glycomics are carbohydrate arrays, which provide biochemical information on carbohydrate-protein interactions in a high throughput manner that is essential for a comprehensive mapping of glycomics.

Glycoarray technology requires a combination of skills and the objective of the proposal was to bring together an interdisciplinary team of scientists and technologists in Europe for the development and application of ‘Glycoarrays’. Glycoarrays are micro arrays displaying unnatural and natural complex carbohydrate structures, such as those found on cell surfaces and/or attached to proteins and lipids. Such glycoarrays can provide unique tools to identify the many interactions of carbohydrate binding proteins with specific carbohydrate sequences on a cell and organism-wide scale, and thus provide us with a fundamental understanding of these important biological recognition events.

The first challenge in glycoarray technology is the availability of complex carbohydrate probes which can either be obtained by isolation from natural sources or by synthesis. Both approaches were investigated. Natural sources were found to be limited to few structures such as some N-glycans which are abundant in egg proteins. Synthetic processes proved to be more versatile and provide pure material. GPI anchors, glucosamino glycans, N- and O-glycans were synthesised in the programme providing hundreds of probes for attachment to glycoarrays. These carbohydrates were functionalised with a common linkers tailored for attachment to different glycoarray platforms.

Two major glycoarray platforms were developed in this programme – the first platform displayed carbohydrates in microarray format on commercially available glass slides. These slides were highly suitable for studying the binding of labelled proteins with read out by fluorescent spectroscopy, in line with other array platforms that are used commercially for DNA and proteins. A second platform on conducting surfaces such as gold was used for studying glycoenzyme reactions allowing label-free readout by mass spectrometry and surface plasmon resonance spectroscopy.

These array platforms were used to identify a number of carbohydrate-protein interactions in diverse biological areas such as virology, carbohydrate-based cancer biomarkers and congenital disorders of glycosylation (muscular dystrophies). The results of these studies have been published in peer-reviewed journals and provide tools for future developments, such as biomarker discovery and carbohydrate based diagnostics.

In addition to these physical research tools, the network has also developed a number of bioinformatics tools which provide databases for sequence and three dimensional polysaccharide structures.

A combination of the array tools and the bioinformatics databases will be essential to open up the previously specialised and challenging area of glycoscience to the broader scientific community, such that glycoscience and glycomics become integrated as essential parts of postgenomic science and technologies.