Repurposing human kinase inhibitors to create an antibiotic active against drug-resistant Staphylococcus aureus, persisters and biofilms.

New drugs are desperately needed to combat methicillin-resistant Staphylococcus aureus (MRSA) infections. Here, we report screening commercial kinase inhibitors for antibacterial activity and found the anticancer drug sorafenib as major hit that effectively kills MRSA strains. Varying the key structural features led to the identification of a potent analogue, PK150, that showed antibacterial activity against several pathogenic strains at submicromolar concentrations. Furthermore, this antibiotic eliminated challenging persisters as well as established biofilms. PK150 holds promising therapeutic potential as it did not induce in vitro resistance, and shows oral bioavailability and in vivo efficacy. Analysis of the mode of action using chemical proteomics revealed several targets, which included interference with menaquinone biosynthesis by inhibiting demethylmenaquinone methyltransferase and the stimulation of protein secretion by altering the activity of signal peptidase IB. Reduced endogenous menaquinone levels along with enhanced levels of extracellular proteins of PK150-treated bacteria support this target hypothesis. The associated antibiotic effects, especially the lack of resistance development, probably stem from the compound's polypharmacology.

Transcriptomic Profiling Suggests That Promysalin Alters the Metabolic Flux, Motility, and Iron Regulation in Pseudomonas putida KT2440.

Promysalin, a secondary metabolite produced by P. putida RW10S1, is a narrow-spectrum antibiotic that targets P. aeruginosa over other Pseudomonas spp. P. putida KT2440, a nonproducing strain, displays increased swarming motility and decreased pyoverdine production in the presence of exogenous promysalin. Herein, proteomic and transcriptomic experiments were used to provide insight about how promysalin elicits responses in PPKT2440 and rationalize its species selectivity. RNA-sequencing results suggest that promysalin affects PPKT2440 by (1) increasing swarming in a flagella-independent manner; (2) causing cells to behave as if they were experiencing an iron-deficient environment, and (3) shifting metabolism away from glucose conversion to pyruvate via the Entner-Doudoroff pathway. These findings highlight nature's ability to develop small molecules with specific targets, resulting in exquisite selectivity.

PDZ-domain-directed basolateral targeting of the peripheral membrane protein FRMPD2 in epithelial cells.

Multi-PDZ (PSD-95/Discs large/Zonula-occludens-1) domain proteins play a crucial role in the establishment and maintenance of cell polarization. The novel multi-PDZ domain protein FRMPD2 is a potential scaffolding protein consisting of an N-terminal KIND domain, a FERM domain and three PDZ domains. Here we show that FRMPD2 is localized in a polarized fashion in epithelial cells at the basolateral membrane and partially colocalizes with the tight-junction marker protein Zonula-occludens-1. Downregulation of FRMPD2 protein in Caco-2 cells is associated with an impairment of tight junction formation. We find that the FERM domain of FRMPD2 binds phosphatidylinositols and is sufficient for membrane localization. Moreover, we demonstrate that recruitment of FRMPD2 to cell-cell junctions is strictly E-cadherin-dependent, which is in line with our identification of catenin family proteins as binding partners for FRMPD2. We demonstrate that the FERM domain and binding of the PDZ2 domain to the armadillo protein p0071 are required for basolateral restriction of FRMPD2. Moreover, the PDZ2 domain of FRMPD2 is sufficient to partially redirect an apically localized protein to the basolateral membrane. Our results provide novel insights into the molecular function of FRMPD2 and into the targeting mechanism of peripheral membrane proteins in polarized epithelial cells.