The modification of serines/threonines on cytosolic proteins in higher eukaryotes with O-linked N-acetylglucosamine (O-GlcNAc) is an essential, abundant and dynamic post-translational modification. O-GlcNAc has been implicated in a wide range of cellular processes, including transcription, the cell cycle, signal transduction networks and protein folding, and shows interplay with regulatory protein phosphorylation. Despite recent biochemical and structural advances, our understanding of the precise functional implications of O-GlcNAc is still limited and we do not understand how O-GlcNAc transferase (OGT) and O-GlcNAc hydrolase (OGA), single essential genes in metazoa, together build the dynamic O-GlcNAc proteome. Interestingly, O-GlcNAc appears to be particularly abundant in the brain and recent proteomics studies have identified O-GlcNAc on proteins that are involved in the development and progression of neurodegenerative diseases - Tau in Alzheimer's disease, the PrP prion protein in Creutzfeldt-Jakob disease and a-synuclein in Parkinson's disease. Furthermore, mutations in the OGT gene give rise to X-linked mental retardation.

My lab aims to transform our understanding of the mechanisms, regulation and functional implications of the O-GlcNAc modification in the brain and neurodegenerative disease using a multidisciplinary chemical, biochemical, structural, cell biological and genetic approaches. Recently we have been using CRISPR-Cas9 genome editing in stem cells, Drosophila and vertebrate models to explore the effects of OGT catalytic activity on development and disease.

Key publications:

1. S. Pathak, V.S. Borodkin, O. Albarbarawi, D.G. Campbell, A. Ibrahim and D.M.F. van Aalten, "O-GlcNAcylation of TAB1 modulates TAK1-mediated cytokine release", EMBO J. (2012), 31, 1394-1404. PDF  Pubmed
2. M. Schimpl, X. Zheng, V.S. Borodkin, D.E. Blair, A.T. Ferenbach, A.W. Schuettelkopf, I. Navratilova, T. Aristotelous, O. Albarbarawi, D.A. Robinson, M.A. MacNaughtan and D.M.F. van Aalten, "O-GlcNAc transferase invokes nucleotide sugar pyrophosphate participation in catalysis", Nature Chem.Biol. (2012), 8, 969-974. PDF + Commentary PDF  Pubmed
3. N. Selvan, D. Mariappa, H.W.P. van den Toorn, A.J.R. Heck, A.T. Ferenbach and D.M.F. van Aalten, "The early metazoan Trichoplax adhaerens possesses a functional O-GlcNAc system", J.Biol.Chem. (2015), 290, 11969-11982. PDF Pubmed 25778404
4. D. Mariappa, X. Zheng, M. Schimpl, O. Raimi, A.T. Ferenbach, H.A.J. Mueller and D.M.F. van Aalten, "Dual functionality of O-GlcNAc transferase is required for Drosophila development", Open Biol. (2015), 5, 150234. PDF Pubmed 26674417
5. S. Pathak, J. Alonso, M. Schimpl, K. Rafie, D.E. Blair, V.S. Borodkin, A.W. Schuettelkopf, O. Albarbarawi and D.M.F. van Aalten, "The active site of O-GlcNAc transferase imposes constraints on substrate sequence", Nature Struct.Mol.Biol. (2015), 22, 744-750. PDF Pubmed 26237509
6. N. Selvan, R. Williamson, D. Mariappa, D.G. Campbell, R. Gourlay, A.T. Ferenbach, T. Aristotelous, I. Hopkins-Navratilova, M. Trost and Daan M. F. van Aalten, "Native enrichment of the Drosophila O-GlcNAc proteome reveals candidate conveyors of the supersex combs phenotype", Nature Chem.Biol. (2017), in press.

 

Targeting the cell wall of human pathogenic fungi

The cell wall of the opportunistic fungal pathogens Candida albicans and Aspergillus fumigatus is a dynamic and multi-layered structure consisting of the sugar polymers chitin, glucan and (galacto)mannan. 

Despite decades of work, there are huge gaps in our knowledge of the enzymes responsible for cell wall biogenesis. This is particularly pressing given the significant rise of fatal fungal infections in immunocompromised patients, and thus the need for novel, properly genetically and chemically validated, drug targets. In the lab we are probing the “Achilles heel” of cell wall synthesis – the production of the sugar nucleotides UDP-Glc, UDP-GlcNAc and GDP-Man that will cut deep into the essential wall biosynthetic machinery. Using state-of-the-art techniques we genetically, structurally and chemically validate enzymes from these sugar nucleotide biosynthetic pathways as antifungal targets, with a particular focus on fragment-based inhibitor discovery. 

Key publications:

1. R. Hurtado-Guerrero, A.W. Schuettelkopf, I. Mouyna, A.F.M. Ibrahim, S. Shepherd, T. Fontaine, J.P. Latge, and D.M.F. van Aalten, "Molecular mechanisms of yeast cell wall glucan remodeling", J.Biol.Chem. (2009), 284, 8461-8469.
2. C.L. Rush, A.W. Schuettelkopf, R. Hurtado-Guerrero, D.E. Blair, A.F.M. Ibrahim, S. Desvergnes, I.M. Eggleston and D.M.F. van Aalten, "Natural product-guided discovery of a fungal chitinase inhibitor", Chem.Biol. (2010), 17, 1275-1281.
3. W. Fang, T. Du, O.G. Raimi, R. Hurtado-Guerrero, M.D. Urbaniak, A.F.M. Ibrahim, M.A.J. Ferguson, C. Jin and D.M.F. van Aalten, "Genetic and structural validation of Aspergillus fumigatus UDP-N-acetylglucosamine pyrophosphorylase as an antifungal target", Mol.Microbiol. (2013), 89, 479-493. PDF  Pubmed 23750903
4. A. Striebeck, D.A. Robinson, A.W. Schuettelkopf and D.M.F. van Aalten, "Yeast Mnn9 is both a priming glycosyltransferase and an allosteric activator of mannan biosynthesis", Open Biol. (2013), 3, 130022. PDF  Pubmed 24026536
5. H.C. Dorfmueller, A.T. Ferenbach, V.S. Borodkin and D.M.F. van Aalten, "A structural and biochemical model of processive chitin synthesis", J.Biol.Chem. (2014), 289, 23020-23028. PDF Pubmed 24942743
6. W. Fang, D.A. Robinson, O.G. Raimi, D.E. Blair, J.R. Harrison, D.E.A. Lockhart, L.S. Torrie, G.F. Ruda, P.G. Wyatt, I.H. Gilbert and D.M.F. van Aalten, "N-myristoyltransferase is a cell wall target in Aspergillus fumigatus", ACS Chem.Biol. (2015), 10, 1425−1434. PDF Pubmed 25706802