Recognition of specific host epitopes by uropathogenic E. coli (UPEC) is a process essential to initiating infection of the urinary tract and kidneys. This process is most often mediated by carbohydrate-binding proteins (lectins) called adhesins that are assembled at the tips of hairlike extracellular appendages called pili. Recognition of mono- and poly-mannose epitopes on host uroplakins by the adhesin FimH is an essential step in urinary tract infection (UTI), while recognition of galabiose in the kidney by PapG is essential to E. coli pyleonephritis. Expression of UPEC pili occurs from pilus operons, which are identifiable by a series of genes encoding an usher assembly platform, a chaperone to prevent periplasmic assembly, a pilus terminator, a major pilus subunit, tip adapter subunits and, invariably at the end of the operon, an adhesin. While the fim and pap operons are well-studied, there are eight additional UPEC pilus operons, each with its own adhesin. This proposal utilizes human glycan arrays to determine the carbohydrate specificity of these eight adhesins as well as a computational method for extrapolating which host tissues these adhesins may recognize. A parallel aim is to determine the structural basis of this fundamental host-pathogen recognition event for each adhesin using a high-throughput crystallography pipeline. A final key element is the development of cell-based hemagglutination assays for validation of adhesin carbohydrate specificity and its structural basis. Long-term, this work sets the stage for development of antivirulence therapies targeting specific adhesins, similar to the recently-developed set of mannoside drugs targeting FimH to cure urinary tract infection.
Escherichia coli urinary tract infection is the most common infection in the Western world. Only one-fifth of the total number of uropathogenic E. coli host-recognition proteins called adhesins are well studied, yet these proteins may represent essential factors in causing urinary tract and kidney infection. This proposal seeks define the molecular basis of how these understudied adhesins recognize E. coli's human host, setting the stage for development of therapeutic drugs that target this recognition.