Glycophage arrays for the discovery of biomarkers in disease

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DESCRIPTION (provided by applicant): Many biological processes throughout the lifespan of a living organism are governed by discrete sugar structures and their interaction with protein and lipid molecules. Such carbohydrates play essential roles in processes such as cell-cell recognition, adhesion, cell activation and host- pathogen interactions. In humans, variations in the synthesis of complex carbohydrates are known to cause pathologies including cancer, retrovirus infection and disorders of the heart, lung and blood. Substantial information has been learned about carbohydrate function from studies employing traditional analytical tools, yet there remains a demand for high-throughput methods that allow for the characterization and engineering of protein-carbohydrate interactions. High-throughput methods for characterizing carbohydrate/antigen interactions have been lacking for a variety of reasons including the absence of template driven synthesis and the significant structural complexity of glycans. However, even the current toolkit for detecting changes in glycan structure has shown great potential in the discovery of novel biomarkers for diseases such as cancer and HIV. Recently, it was discovered that the Campylobacter jejuni asparagine-linked (N-linked) protein glycosylation system can be functionally transferred into E. coli, conferring the ability to glycosylate proteins. Although the bacterial N-glycan is structurally different from its eukaryotic counterparts, such an accomplishment opens the door for engineered glycosylation reactions that mimic the processing of N-glycans in humans and other higher mammals. Glycobia seeks to apply such "bacterial glycoengineering" for the development of diagnostic and therapeutic agents. Towards this goal, the objective of this particular application is to synthesize a functional microarray of phage-displayed glycans (Aim 1) and use the microarray to detect basic protein-carbohydrate interactions (Aim 2). These studies should lay the necessary foundation for future work in expanding the diversity of phage-displayed glycans and analyzing carbohydrate signatures in complex serum. These studies are significant because they should (i) provide an analytical tool that overcomes the current bottlenecks of glycan microarray synthesis and (ii) enable the future synthesis of novel glycoconjugates for research, industrial and therapeutic applications. Public Health Relevance: Abnormalities in the assembly of complex sugars are known to be associated with a multitude of diseases including cancer, retrovirus infection and disorders of the heart, lung and blood. Carbohydrate-based array systems have emerged as the preferred methodology for analyzing carbohydrate-antigen interactions underlying these disorders, however the future utility of these arrays hinges critically on the ability to generate and recover diverse glycans for immobilization. The focus of these studies is the development of functional microarrays comprised of phage- displayed glycans for probing carbohydrate-antigen interactions.