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 that address the serious consequences of resistance development. In the past decade bacterial cell surface glycoconjugates, including the lipopolysaccharide (LPS) component of the outer cell wall and cell surface N- and O-linked glycoproteins of several medically relevant Gram-negative bacteria pathogens, have been characterized in molecular detail and found to be essential for host-dependent virulence and pathogenicity. We propose to employ a high-throughput small-molecule screening strategy to identify potent and selective inhibitors of an essential step in the biosynthesis of di-N-acetylbacillosamine (diNAcBAc), which is a highly modified saccharide that features as an essential building block in the cell-surface glycoconjugates of many Gram-negative pathogens. The current studies target the discovery of small molecule inhibitors of the enzyme PglD, which is an acetyl-CoA-dependent acetyl transferase that carries out the final step in the conversion of UDP-GlcNAc into UDP-diNAcBac in the N-linked protein glycosylation pathway of the enteropathogen Campylobacter jejuni. Phenotypic studies establish that UDP-diNAcBac is an obligatory intermediate in the pathway that ultimately affords bacterial cell-surface N-linked glycoproteins that are involved in host cell adhesion, invasion and colonization. Therefore, smal-molecule inhibitors that result from these studies would be incisive chemical tools for elucidating the fundamental roles of highly modified saccharides in microbial virulence and pathogenesis. Additionally, the probes would represent novel leads in the development of new therapeutic agents and validate a new class of antibiotic target. 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. This research seeks to exploit these essential virulence-associated pathways by developing inhibitors to block production of critical building blocks in glycoconjugate assembly, thus developing new tools to understand the roles of glycoconjugates in microbial pathogens and validate new targets for antimicrobial therapy.