The Laboratory of Chemical Glycobiology

Glycobiology is the study of the structures and roles of carbohydrates in biology. Contrary to popular belief, carbohydrates are not simply energy sources but play many essential roles in cell and organismal biology. Various different types of carbohydrate building blocks are known and these can be linked together in various ways by carbohydrate processing enzymes.  The resulting carbohydrate structures are attached to other molecules found in cells including proteins and lipids. The carbohydrate structures present on the resulting glycoconjugates continue to be uncovered as important factors in health and disease.

The laboratory for chemical glycobiology headed by Dr. Vocadlo is engaged in the study of; (i) carbohydrate processing enzymes that act on glycoconjugates, (ii) the development of chemical tools to both perturb the action of these enzymes as well as to monitor glycoconjugates, (iii) and the use of these chemical tools to gain new understanding as to how these enzymes and glycoconjugates mediate biological processes.  To realize these aims we study the structures of glycoconjugates using various analytical approaches. We also synthesize substrates to study the specificities of carbohydrate processing enzymes and use the methods of physical organic chemistry and biochemistry to understand how they work to process glycoconjugates.  Insights gained through such studies are used to design chemical probes of these enzymes, with a focus on enzyme inhibitors.  These probes are validated in vitro, in cells, and in vivo as appropriate.  A central objective is to create selective probes of carbohydrate processing enzymes that can be used to evaluate the roles of carbohydrate structures of interest in health and disease. 

The O-GlcNAc post-translational modification

The modification of serine and threonine residues of nuclear and cytoplasmic proteins with N-acetylglucosamine residues is known as the O-GlcNAc post-translational modification. This modification is abundant within all multicellular eukaryotes and its levels are maintained by only two enzymes.  A glycosyltransferase known as O-GlcNAc transferase (OGT) acts to install O-GlcNAc at sites of modification. A glycoside hydrolase known as O-GlcNAcase (OGA) acts to remove this modification from proteins. The coordinated action of these enzymes results in the cycling of O-GlcNAc on proteins at a rate that is faster than the turnover of the protein itself.  O-GlcNAc has also been shown in some cases to be reciprocal with serine and threonine phosphorylation, either by modification of the same residue or nearby residues. O-GlcNAc is therefore a dynamic modification that is able to modulate phosphorylation within signaling pathways.  Accordingly, this unique modification has been implicated in stress response and various disease states including neurodegeneration.  O-GlcNAc also plays fundamental roles in biology as was recently uncovered in a collaborative effort between the laboratory and the laboratories of Drs. Sinclair, Honda, and Brock, where it was found that OGT is a member of the polycomb group family of proteins, which are key regulators of gene expression. Owing to the interest in the basic roles of O-GlcNAc we have carried out detailed studies of both OGA and OGT. We have established the catalytic mechanism of OGA and developed the first nanomolar selective inhibitors of this enzyme.  We have gone on to develop highly selective inhibitors of OGA that cross the blood brain barrier to increase O-GlcNAc levels in the central nervous system and have proposed OGA as a potential therapeutic target for the treatment of Alzheimer disease. More recently, we have gained insights into the glycosyltransferase OGT and have developed a new Trojan horse strategy to inhibit the OGT in cells with single digit micromolar potency. We are continuing our research in the area, developing and refining chemical probes to determine their generality, as well as using these powerful reagents to study the basic biological roles of O-GlcNAc. We collaborate extensively with researchers world-wide in order to generate improved probes as well as gain insight into the functions of O-GlcNAc including a long standing collaboration with Dr. Davies at the University of York.

The peptidoglycan confers structural stability to all bacteria.  Bacteria carefully maintain and recycle the peptidoglycan using a large panel of enzymes. These peptidoglycan processing enzymes are the target of many antibiotics including, most notably, the widely used class of antibiotics known as beta-lactams.  Various Gram-negative bacteria, including the harmful opportunistic pathogen known as Pseudomonas aeruginosa, have evolved a remarkable antibiotic resistance mechanism. In these bacteria, fragments of the peptidoglycan are sensed by proteins inside the cell and when certain beta-lactams are present the concentrations of some of these fragments are altered and this can trigger the production of a beta-lactamase known as AmpC.  More disturbing is that bacteria can evolve constant high-level production of AmpC and this leads to inactivation of many frontline beta-lactams; contributing significantly to the failure of antimicrobial therapy in the treatment of various bacterial infections. We have undertaken a program of research to interfere with the sensing of these peptidoglycan fragments as an approach to blocking the development as well as reversing antibiotic resistance. We are studying the enzymes involved in recycling these peptidoglycan fragments and have developed selective inhibitors that target these enzymes over functionally related human enzymes.  We have also developed probes of one class of enzyme that can be used to probe the levels of these enzymes in bacterial cells. Our current aims are to generate improved inhibitors as well as to improve our understanding of the protein that acts to sense the peptidoglycan fragments.  The work is carried out through a long-standing collaboration with Dr. Brian Mark at the University of Manitoba.

Research opportunities

The laboratory is a highly collaborative environment where researchers work in a team to solve challenging problems in chemical glycobiology.  Various other projects are ongoing that are not listed here.  For other ongoing projects and more details of current projects please selected publications accessed though the "Publications" link at the bottom left of this page. Depending on the project, team members have the opportunity to gain exposure to methods ranging from carbohydrate synthesis, protein expression, molecular biology, mechanistic enzymology, capillary electrophoresis, mass spectrometry, tissue culture, and basic animal handling. The laboratory enjoys extensive collaborations both within North Amerca as well as overseas including  long-standing collaborations with with Dr. Boraston  at University of Victoria, Dr. Davies at the Univesrity of York, Dr. Mark at the University of Manitoba, Dr. Stubbs at the University of Western Australia,  and Drs. Sinclair., Brock and Honda.  Researchers are provided with mentoring according to their experience so as to aid their scientific development and enable them to realize their professional goals.  Researchers are encouraged to use creative strategies to progress their projects and, if needed, visit other laboratories in order to learn necessary skills. The laboratory researchers number between 10 to 14 researchers including post-doctoral fellows, PhD candidates, MSc candidates, and one or two undergraduate students. If you are excited about interdisciplinary science, a talented team player, enjoy basic experimental research in chemistry, biochemistry, or cell biology, and are interested in joining the laboratory feel free to contact Dr. Vocadlo by email.

Requests for materials

The laboratory for chemical biology provides clones as well as various available inhibitors to academic researchers.  Please note that Simon Fraser University requires that all materials sent by the laboratory be the subject of a Material Transfer Agreement (MTA).  For requests for materials or for potential collaboration please contact Dr. Vocadlo by email.