Laura Keller

All Publications

• Integration of bioinformatic and chemoproteomic tools for the study of enzyme conservation in closely related bacterial species. Methods in enzymology Keller, L. J., Lakemeyer, M., Bogyo, M. 2022; 664: 1-22

  Abstract

  Activity-based protein profiling (ABPP) is a commonly utilized technique to globally characterize the endogenous activity of multiple enzymes within a related family. While it has been used extensively to identify enzymes that are differentially active across various mammalian tissues, recent efforts have expanded this technique to studying bacteria. As ABPP is applied to diverse sets of bacterial strains found in microbial communities, there is also an increasing need for robust tools for assessing the conservation of enzymes across closely related bacterial species and strains. In this chapter, we detail the integration of gel-based ABPP with basic bioinformatic tools to enable the analysis of enzyme activity, distribution, and homology. We use as an example the family of serine hydrolases identified in the skin commensal bacterium Staphylococcus epidermidis.

  View details for DOI 10.1016/bs.mie.2021.11.017

  View details for PubMedID 35331369

• Chemiluminescent Protease Probe for Rapid, Sensitive, and Inexpensive Detection of Live Mycobacterium tuberculosis. ACS central science Babin, B. M., Fernandez-Cuervo, G., Sheng, J., Green, O., Ordonez, A. A., Turner, M. L., Keller, L. J., Jain, S. K., Shabat, D., Bogyo, M. 2021; 7 (5): 803-814

  Abstract

  Tuberculosis (TB) is a top-ten cause of death worldwide. Successful treatment is often limited by insufficient diagnostic capabilities, especially at the point of care in low-resource settings. The ideal diagnostic must be fast, be cheap, and require minimal clinical resources while providing high sensitivity, selectivity, and the ability to differentiate live from dead bacteria. We describe here the development of a fast, luminescent, and affordable sensor of Hip1 (FLASH) for detecting and monitoring drug susceptibility of Mycobacterium tuberculosis (Mtb). FLASH is a selective chemiluminescent substrate for the Mtb protease Hip1 that, when processed, produces visible light that can be measured with a high signal-to-noise ratio using inexpensive sensors. FLASH is sensitive to fmol of recombinant Hip1 enzyme in vitro and can detect as few as thousands of Mtb cells in culture or in human sputum samples within minutes. The probe is highly selective for Mtb compared to other nontuberculous mycobacteria and can distinguish live from dead cells. Importantly, FLASH can be used to measure antibiotic killing of Mtb in culture with greatly accelerated timelines compared to traditional protocols. Overall, FLASH has the potential to enhance both TB diagnostics and drug resistance monitoring in resource-limited settings.

  View details for DOI 10.1021/acscentsci.0c01345

  View details for PubMedID 34079897

• Identification of covalent inhibitors that disrupt M. tuberculosis growth by targeting multiple serine hydrolases involved in lipid metabolism. Cell chemical biology Babin, B. M., Keller, L. J., Pinto, Y., Li, V. L., Eneim, A. S., Vance, S. E., Terrell, S. M., Bhatt, A. S., Long, J. Z., Bogyo, M. 2021

  Abstract

  The increasing incidence of antibiotic-resistant Mycobacterium tuberculosis infections is a global health threat necessitating the development of new antibiotics. Serine hydrolases (SHs) are a promising class of targets because of their importance for the synthesis of the mycobacterial cell envelope. We screen a library of small molecules containing serine-reactive electrophiles and identify narrow-spectrum inhibitors of M. tuberculosis growth. Using these lead molecules, we perform competitive activity-based protein profiling and identify multiple SH targets, including enzymes with uncharacterized functions. Lipidomic analyses of compound-treated cultures reveal an accumulation of free lipids and a substantial decrease in lipooligosaccharides, linking SH inhibition to defects in cell envelope biogenesis. Mutant analysis reveals a path to resistance via the synthesis of mycocerates, but not through mutations to SH targets. Our results suggest that simultaneous inhibition of multiple SH enzymes is likely to be an effective therapeutic strategy for the treatment of M. tuberculosis infections.

  View details for DOI 10.1016/j.chembiol.2021.08.013

  View details for PubMedID 34599874

• Characterization of Serine Hydrolases Across Clinical Isolates of Commensal Skin Bacteria Staphylococcus epidermidis Using Activity-Based Protein Profiling. ACS infectious diseases Keller, L. J., Lentz, C. S., Chen, Y. E., Metivier, R. J., Weerapana, E. n., Fischbach, M. A., Bogyo, M. n. 2020

  Abstract

  The bacterial genus Staphylococcus comprises diverse species that colonize the skin as commensals but can also cause infection. Previous work identified a family of serine hydrolases termed fluorophoshonate-binding hydrolases (Fphs) in the pathogenic bacteria Staphylococcus aureus, one of which, FphB, functions as a virulence factor. Using a combination of bioinformatics and activity-based protein profiling (ABPP), we identify homologues of these enzymes in the related commensal bacteria Staphylococcus epidermidis. Two of the S. aureus Fph enzymes were not identified in S. epidermidis. Using ABPP, we identified several candidate hydrolases that were not previously identified in S. aureus that may be functionally related to the Fphs. Interestingly, the activity of the Fphs vary across clinical isolates of S. epidermidis. Biochemical characterization of the FphB homologue in S. epidermidis (SeFphB) suggests it is a functional homologue of FphB in S. aureus, but our preliminary studies suggest it may not have a role in colonization in vivo. This potential difference in biological function between the Fphs of closely related staphylococcal species may provide mechanisms for specific inhibition of S. aureus infection without perturbing commensal communities of related bacteria.

  View details for DOI 10.1021/acsinfecdis.0c00095

  View details for PubMedID 32298574

• Activity-based protein profiling in bacteria: Applications for identification of therapeutic targets and characterization of microbial communities. Current opinion in chemical biology Keller, L. J., Babin, B. M., Lakemeyer, M., Bogyo, M. 2019; 54: 45–53

  Abstract

  Activity-based protein profiling (ABPP) is a robust chemoproteomic technique that uses activity-based probes to globally measure endogenous enzymatic activity in complex proteomes. It has been utilized extensively to characterize human disease states and identify druggable targets in diverse disease conditions. ABPP has also recently found applications in microbiology. This includes using activity-based probes (ABPs) for functional studies of pathogenic bacteria as well as complex communities within a microbiome. This review will focus on recent advances in the use of ABPs to profile enzyme activity in disease models, screen for selective inhibitors of key enzymes, and develop imaging tools to better understand the host-bacterial interface.

  View details for DOI 10.1016/j.cbpa.2019.10.007

  View details for PubMedID 31835131

• Fluorescent Triazole Urea Activity-Based Probes for the Single-Cell Phenotypic Characterization of Staphylococcus aureus. Angewandte Chemie (International ed. in English) Chen, L. n., Keller, L. J., Cordasco, E. n., Bogyo, M. n., Lentz, C. S. 2019; 58 (17): 5643–47

  Abstract

  Phenotypically distinct cellular (sub)populations are clinically relevant for the virulence and antibiotic resistance of a bacterial pathogen, but functionally different cells are usually indistinguishable from each other. Herein, we introduce fluorescent activity-based probes as chemical tools for the single-cell phenotypic characterization of enzyme activity levels in Staphylococcus aureus. We screened a 1,2,3-triazole urea library to identify selective inhibitors of fluorophosphonate-binding serine hydrolases and lipases in S. aureus and synthesized target-selective activity-based probes. Molecular imaging and activity-based protein profiling studies with these probes revealed a dynamic network within this enzyme family involving compensatory regulation of specific family members and exposed single-cell phenotypic heterogeneity. We propose the labeling of enzymatic activities by chemical probes as a generalizable method for the phenotyping of bacterial cells at the population and single-cell level.

  View details for PubMedID 30768830