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ANR funded project

JCJC - SVSE 5 - Physique, chimie du vivant et innovations biotechnologiques (JCJC SVSE 5) 2012
Projet HepLibScreen

Chemo-enzymatic Design of Heparan sulfate oligosaccharide libraries; Evaluation of protein HS binding specificities

Heparan Sulphate (HS) are sulphated polysaccharides ubiquitously present at higher eukaryotes cell surfaces and extracellular matrices. They participate in essential biological processes such as development, inflammatory responses, cell migration, blood coagulation. They are also used by pathogens during cell infection and play an important role in cancer development.
The main function of this unique class of polysaccharides which belong to the glycosaminoglycan family is to interact with proteins. They are anchored to protein cores to form proteoglycans, and their localisation at cell surfaces and matrices places them in an ideal position to mediate interactions between cells and their environment. HS bind to growth factors, cytokines, chemokines, enzymes and consequently mediate their localisation, their activity or their interaction with a specific cell surface receptor.
The structure/function paradigm of HS resides in the intrinsic variability generated during biosynthesis through the concerted action of several modifying enzymes. These modifications and in particular sulphations are tightly regulated during the biosynthesis of HS and depend specifically on the cell type and its environment. Cells are thus able to produce specific HS sequences that will mediate the binding of proteins and in turn modulate biological processes.
While several hundreds proteins have been identified as ligands for Heparan Sulphate, identifying the determinants of the interaction specificity remains very challenging. Indeed the biosynthesis of HS is able to generate several thousands of different modifications motifs. The lack of information is largely due to the high heterogeneity of HS and consecutively the difficulty to purify defined sulphation motifs, test the interactions and characterize the protein-bound oligosaccharidic sequence.
We thus propose to generate isotopically labelled (13C/15N) chemo-enzymatic HS libraries. These libraries will constitute great tools as their labelling allows at the same time to identify their chemical structures and to monitor their interactions with proteins by Nuclear Magnetic Resonance. Two proteins that have been extensively studied in our group and for which the binding to HS is critical for their function, IFN?, a pro-inflammatory cytokine and the chemokine CXCL12a will be tested in interaction with the libraries.
The best-affinity HS will be selected by titration of the proteins to size-defined HS fragments, chromatographic isolation of the protein-HS complexes and NMR characterisation of the bound ligands. We will also use NMR to directly monitor interactions between mixtures of HS fragments and proteins. The oligosaccharides possessing the best affinity for the proteins will be isolated and fully characterised. Atomic resolution models of the best protein-HS complexes will be solved by Nuclear Magnetic Resonance, making full use of 13C/15N labelled ligands in conjunction with labelled or unlabelled protein.
This project should permit to define of the HS motifs preferentially bound by the two proteins studied and also to characterise the structural determinants of the binding. These informations are highly invaluable in order to further study their biological function and also to design HS-based molecules that are able to modulate their function.

Partners

IBS/SAGAG Institut de Biologie Structurale groupe SAGAG

ANR grant: 139 999 euros
Beginning and duration: janvier 2013 - 24 mois

 

ANR Programme: JCJC - SVSE 5 - Physique, chimie du vivant et innovations biotechnologiques (JCJC SVSE 5) 2012

Project ID: ANR-12-JSV5-0006

Project coordinator:
Monsieur cedric LAGURI (Institut de Biologie Structurale groupe SAGAG)
cedric.laguri@nullibs.fr

 

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The project coordinator is the author of this abstract and is therefore responsible for the content of the summary. The ANR disclaims all responsibility in connection with its content.