Rebecca Louise Miller
Blegdamsvej 3, 2200 København N.
Glycosylation is one of the most common post-translational modifications (PTMs) of proteins essential to all eukaryotic systems, where glycans (ie. carbohydrates) are covalently attached to the protein. The biological role of glycosylation in the extracellular matrix is vast, including; trafficking cells in the immune system, cell adhesion, recognizing foreign materials, controlling cell metabolism, to providing cartilage and tendon flexibility. Research and development to harness these extracellular glycomes, even when limited to the simplest forms of glycosylation, have led to the approvals of over 200 biologicals to treat diverse diseases with a global market value of €250 billion and a 10% annual growth. Glycosaminoglycan (GAG) polysaccharides is one example of these carbohydrates, they have relatively simple repeating disaccharide backbones, however, their complexity and structural diversity arises through extensive sulfation of these disaccharides and my group focus predominately on this complex molecule.
Mammalian glycosaminoglycans (GAGs) are sulfated polysaccharides commonly exemplified by their most abundant forms: heparin, heparan sulfate (HS) and chondroitin/dermatan sulfate (CS/DS). GAGs are major components of the extracellular matrix that regulate many diverse functions, such as cell migration, injury, anticoagulation, angiogenesis, inflammation, as well as normal growth and development. GAGs are primarily defined by their disaccharide repeats that are extensively sulfated in distinct patterns along the chain. These sulfation codes are the source of the structural complexity and heterogeneity of GAGs, which dictate the functional properties. Despite the biological importance of GAGs, analysis continues to be challenging. Illustrating this conundrum is the widely used anti-coagulant drug heparin, a highly sulfated heparan sulfate (HS) isolated from animals, which is a heterogenous mixture lacking complete structural characterization. Whilst heparin is successful in preventing and treating thromboembolic events, a great variety of other biological effects are attributed to the heterogeneous heparin, including anti-inflammatory, anti-metastatic, and anti-viral properties. Given that the effects are expected to arise from distinct sulfation codes in GAGs, our knowledge of which codes lead to therapeutic effects is very limited due to the lack of tools to read the sulfation codes in GAGs, where my group works on the development of tools and technologies to define these sulfation code to develop homogenous GAG chains as therapeutics.
The biosynthesis of GAGs involves a large number of glycosyltransferases and over 40 sulfotransferases. Using the KO/KI of genes orchestrating the biosynthesis of GAGs in CHO cells, we have been able to produce cell-derived libraries that display distinct heparin, HS, CS, and DS on the cell surface . Therefore, my groups aims to investigate how the sulfation codes lead to specific biochemical properties. The availability of this GAG library (i) advances the dissection of these sulfation codes into structure-function relationships, (ii) enables the ability to tailor the design of homogenous GAG molecules with the desired biological effects, such as anti-coagulant, anti-inflammatory or anti-viral properties, and (iii) enables the development of analytical tools and technology development, including a variety of mass spectrometry instruments and single molecule imaging modalities of GAG:protein complexes (mass photometry), and (iv) sparks new strategies for molecular dissection of GAG specific roles such as proliferation, adhesion, angiogenesis, and protein gradients (such as TGF-beta, Wnt) involved in growth and development.