Alley, D. | bioRxiv Science

bioRxiv2025

Selectivity of the time-dependent M. tuberculosis LeuRS inhibitor ganfeborole is driven by target vulnerability

Ganfeborole (GSK3036656) inhibits the Mycobacterium tuberculosis leucyl-tRNA-synthetase (mtLeuRS) and is in phase 2a clinical trials for the treatment of tuberculosis. Here we show that ganfeborole is a time-dependent inhibitor of mtLeuRS (IC50 1 nM) and generates a post-antibiotic effect of 77 h at 50xMIC (MIC 0.058 M) with M. tuberculosis H37Rv (Mtb), indicating that mtLeuRS is a highly vulnerable drug target and supporting the excellent in vivo efficacy of the drug. Ganfeborole is also a potent time-dependent inhibitor of Escherichia coli LeuRS (ecLeuRS, IC50 2 nM), however no antibacterial activity is observed towards E. coli up to 1 mM ganfeborole despite the observation that less potent ganfeborole analogs have antibacterial activity. To rationalize this observation, we propose that ganfeborole forms a complex with AMP that binds to the ecLeuRS editing site but does not impact aminoacylation. In support, addition of 12.5 M norvaline generates a ganfeborole MIC of 0.4 M since ecLeuRS is unable to hydrolyze norvaline-tRNALeu. Additionally, mutations that reduce the affinity and residence time of ganfeborole-AMP on ecLeuRS result in antibacterial activity. We propose that the activity of ganfeborole towards Mtb is because mtLeuRS is a highly vulnerable target so that only low levels of enzyme need to be inhibited by the ganfeborole-tRNALeu complex in contrast to ecLeuRS, which we previously demonstrated is a low vulnerability target.

biochemistry↗

bioRxiv2024

The L1CAM SAX-7 is an antagonistic modulator of Erk signaling

L1CAMs are immunoglobulin superfamily cell adhesion molecules that ensure proper nervous system development and function. In addition to being associated with the autism and schizophrenia spectrum disorders, mutations in the L1CAM family of genes also underlie distinct developmental syndromes with neurological conditions, such as intellectual disability, spastic paraplegia, hypotonia and congenital hydrocephalus. Studies in both vertebrate and invertebrate model organisms have established conserved neurodevelopmental roles for L1CAMs; these include axon guidance, dendrite morphogenesis, synaptogenesis, and maintenance of neural architecture, among others. In Caenorhabditis elegans, L1CAMs, encoded by the sax-7 gene, are required for coordinated locomotion. We previously uncovered a genetic interaction between sax-7 and components of synaptic vesicle cycle, revealing a non-developmental role for sax-7 in regulating synaptic activity. More recently, we determined that sax-7 also genetically interacts with extracellular signal-related kinase (ERK) signaling in controlling coordinated locomotion. C. elegans ERK, encoded by the mpk-1 gene, is a serine/threonine protein kinase belonging to the mitogen-activated protein kinase (MAPK) family that governs multiple aspects of animal development and cellular homeostasis. Here, we show this genetic interaction between sax-7 and mpk-1 occurs not only in cholinergic neurons for coordinated locomotion, but also extends outside the nervous system, revealing novel roles for SAX-7/L1CAM in non-neuronal processes, including vulval development. Our genetic findings in both the nervous system and developing vulva are consistent with SAX-7/L1CAM acting as an antagonistic modulator of ERK signaling.

genetics↗