It is well known that antibiotic resistance is a critical issue in the battle against microbial pathogens. Less well known is the way forward to new approaches in antibacterial therapy. Just in the last few years bacterial cell surface glycoconjugates, including the lipopolysaccharide component of the outer cell wall and cell surface N- and O-linked glycoproteins of numerous medically relevant Gram-negative bacterial pathogens, have been characterized in molecular detail and found to be essential for virulence and pathogenicity. This proposal aims to further define and exploit the pathways that produce the unusual microbe-specific carbohydrate building blocks that are found in these glycoconjugates, thus providing a novel approach to combat bacterial pathogens. This research focuses specifically on the development and in vitro and in vivo validation of inhibitors to enzymes involved in the conversion of UDP-GlcNAc into UDP-di-N-acetyl-bacillosamine (UDP- diNAcBac) in the N- and O-linked protein glycosylation pathways of C. jejuni and N. gonorrhoeae. Since UDP-diNAcBac is a critical intermediate in the pathways that result in the biosynthesis of the bacterial glycoconjugates, these inhibitors could be employed as selective chemical tools to elucidate the fundamental roles of highly modified saccharides in microbial pathogenesis. The experimental approach of the proposed research involves: 1. Application of a structure-guided fragment-based screening (FBS) strategy for the development of potent UDP-diNAcBac biosynthesis inhibitors;2. Evaluation of optimized inhibitors in assays that probe glycoprotein biosynthesis, cell toxicity and the effects of inhibiting glycoprotein biosynthesis on motility, adherence and invasion in the native organism in vivo in C. jejuni and N. gonorrhoeae;3. Establishment of a C. elegans model for C. jejuni and N. gonorrhoeae infectivity and virulence. If successful, this animal model system will be valuable for to assessing inhibitory activity in a simple host;4. Assessment of the effect of C. jejuni UDP-diNAcBac biosynthesis inhibitors in the chick infectivity model in collaboration with Szymanski at the University of Alberta. This research addresses the central hypothesis that the biosynthetic pathways in pathogenic bacteria that lead to highly modified sugar building blocks, such as di-N-acetyl-bacillosamine, represent an "Achilles'heel" that can be exploited in the battle against infectious diseases. The general principles that we develop in these studies will be applicable to other microbial pathogens that implement prokaryote-specific N- and O-linked glycoproteins as virulence factors. If successful, the research will identify new enzyme targets and strategies in the global crisis of combating infectious diseases in the face of escalating antibiotic resistance.
The usual means that humans have used for half a century to defeat their bacterial foes have faltered, as antibiotic resistance of common microbial pathogens presents a growing threat to public health. Recent research has clarified pathways in the production of cell surface glycoproteins that play key roles for deadly Gram-negative bacteria, enabling their access and attack on human cells. Our proposal will support work to exploit these essential virulence-associated pathways by blocking production of critical building blocks in the glycoconjugate assemblies, thus developing an entirely new set of targets for antimicrobial therapy.
|Morrison, Michael J; Imperiali, Barbara (2014) The renaissance of bacillosamine and its derivatives: pathway characterization and implications in pathogenicity. Biochemistry 53:624-38|
|Morrison, Michael J; Imperiali, Barbara (2013) Biosynthesis of UDP-N,N'-diacetylbacillosamine in Acinetobacter baumannii: Biochemical characterization and correlation to existing pathways. Arch Biochem Biophys 536:72-80|
|Morrison, Michael J; Imperiali, Barbara (2013) Biochemical analysis and structure determination of bacterial acetyltransferases responsible for the biosynthesis of UDP-N,N'-diacetylbacillosamine. J Biol Chem 288:32248-60|