Biology subjects

Levine, S. R.

Publications and source records attributed to Levine, S. R..

3 recordsLinked to original sources

bioRxiv2025

Comprehensive identification of β-lactam antibiotic polypharmacology in Mycobacterium tuberculosis

Infections with Mycobacterium tuberculosis (Mtb) cause tuberculosis (TB), which requires at least six months of treatment with multiple antibiotics. There is emergent interest in using {beta}-lactam antibiotics to improve treatment outcomes for patients. These drugs target cell wall biosynthesis, but a comprehensive list of enzymes inhibited by {beta}-lactams in Mtb is lacking. In the current study, we sought to identify and characterize Mtb enzymes inhibited by {beta}-lactam antibiotics using physiological conditions representative of both acute and chronic TB disease. We used new activity-based probes based on the {beta}-lactam antibiotic meropenem due to its approval by the World Health Organization for TB treatment. Activity-based probes label enzymes based on both substrate specificity and catalytic mechanism, enabling precise identification of drug targets. We identified previously undiscovered targets of meropenem in addition to known cell wall biosynthetic enzymes. We validated {beta}-lactam binding and hydrolysis for six newly identified targets: Rv1723, Rv2257c, Rv0309, DapE (Rv1202), MurI (Rv1338), and LipD (Rv1923). Our results demonstrate that there are at least 30 enzymes in Mtb vulnerable to inhibition by meropenem. This is many more {beta}-lactam targets than historically described, suggesting that efficacy in Mtb is a direct result of polypharmacology.

biochemistry↗

bioRxiv2019

Investigating β-lactam drug targets in Mycobacterium tuberculosis using chemical probes

Tuberculosis is a deadly disease that requires a flexible arsenal of drugs to treat it. Although {beta}-lactam antibiotics are rarely used to treat Mycobacterium tuberculosis (Mtb) infections today, the targets of these drugs are present in the bacterium. Moreover, the cell wall peptidoglycan of Mtb contains an abundance of unusual (3[->]3) cross-links. These cross-links are formed by enzymes called L,D-transpeptidases, which are susceptible to inhibition by the carbapenem class of antibiotics. We developed new small molecule probes to investigate the L,D-transpeptidases and other {beta}-lactam drug targets in Mtb. We synthesized probes based on three classes of antibiotics, a monobactam, cephalosporin, and carbapenem. For the carbapenem, we synthesized a meropenem analogue conjugated to a far-red fluorophore. This probe was particularly useful in identifying active L,D-transpeptidases in protein gel-resolved lysates. Next we analyzed {beta}-lactam targets in lysates from both hypoxic and actively-replicating cultures of Mtb. We identified numerous targets, including transpeptidases, carboxypeptidases, and the {beta}-lactamase BlaC. Overall, we provide evidence that Mtb dynamically regulates the enzymes responsible for maintaining cell wall peptidoglycan and that meropenem is a good inhibitor of those enzymes.

biochemistry↗

bioRxiv2018

Single-cell transcriptomics of the aged mouse brain reveals convergent, divergent and unique aging signatures

The mammalian brain is complex, with multiple cell types performing a variety of diverse functions, but exactly how the brain is affected with aging remains largely unknown. Here we performed a single-cell transcriptomic analysis of young and old mouse brains. We provide a comprehensive dataset of aging-related genes, pathways and ligand-receptor interactions in nearly all brain cell types. Our analysis identified gene signatures that vary in a coordinated manner across cell types and gene sets that are regulated in a cell type specific manner, even at times in opposite directions. Thus, our data reveals that aging, rather than inducing a universal program drives a distinct transcriptional course in each cell population. These data provide an important resource for the aging community and highlight key molecular processes, including ribosomal biogenesis, underlying aging. We believe that this large-scale dataset, which is publicly accessible online (aging-mouse-brain), will facilitate additional discoveries directed towards understanding and modifying the aging process.

neuroscience↗