Biology subjects

Vocat, A.

Publications and source records attributed to Vocat, A..

4 recordsLinked to original sources

bioRxiv2026

Human prostaglandin reductases dearomatize and inactivate benzothiazinone antitubercular drugs

Macozinone (MCZ, PBTZ169) is a potent clinical stage benzothiazinone antitubercular agent that covalently inhibits the essential mycobacterial flavoenzyme DprE1. In some mammals, MCZ undergoes reductive dearomatization to H2MCZ, a Hydride Meisenheimer Complex, identified as the major circulating metabolite in humans. We demonstrate for the first time that the NADPH-dependent human prostaglandin reductases PTGR1 and PTGR2 catalyze MCZ dearomatization into H2MCZ, resulting in loss of antimycobacterial activity. This reaction represents a heretofore undescribed host-mediated metabolic inactivation pathway for a therapeutic agent. Although H2MCZ may constitute a transient reactive intermediate, ex vivo and cellular data indicate that it does not contribute to DprE1 inhibition in vivo. Pharmacological inhibition of PTGR1 and PTGR2 using diclofenac, indomethacin, dicumarol, or the selective inhibitor PTGR2-IN-1 suppresses H2MCZ formation and partially restores MCZ antimycobacterial activity in vitro. Together, our findings uncover a previously unrecognized noncanonical enzymatic mechanism of drug metabolism involving dearomatization in humans. Targeting prostaglandin reductases may represent a strategy to enhance benzothiazinone exposure and efficacy.

pharmacology and toxicology↗

bioRxiv2021

Discovery and Biosynthesis of Persiathiacins: Unusual Polyglycosylated Thiopeptides Active against Multi-drug resistant Tuberculosis

Thiopeptides are ribosomally biosynthesized and post-translationally modified peptides (RiPPs) that potently inhibit the growth of Gram-positive bacteria by targeting multiple steps in protein biosynthesis. The poor pharmacological properties of thiopeptides, in particular their low aqueous solubility, has hindered their development into clinically useful antibiotics. Antimicrobial activity screens of a library of Actinobacterial extracts led to discovery of the novel polyglycosylated thiopeptides persiathiacins A and B from Actinokineospora sp. UTMC 2475 and Actinokineospora sp. UTMC 2448. Persiathiacin A is active against methicillin-resistant Staphylococcus aureus (MRSA) and several Mycobacterium tuberculosis strains, including drug-resistant and multidrug-resistant clinical isolates, and does not significantly affect the growth of ovarian cancer cells at concentrations up to 400 M. In vitro translation assays showed that, like other thiopeptide antibiotics, persiathiacin A targets protein biosynthesis. Polyglycosylated thiopeptides are extremely rare and nothing is known about their biosynthesis. Sequencing and analysis of the Actinokineospora sp. UTMC 2448 genome enabled identification of the putative persiathiacin biosynthetic gene cluster. A cytochrome P450 encoded by this gene cluster catalyses the hydroxylation of nosiheptide in vitro and in vivo, consistent with the proposal that the cluster directs persiathiacin biosynthesis. Several genes in the cluster encode homologues of enzymes known to catalyse the assembly and attachment of deoxysugars during the biosynthesis of other classes of glycosylated natural products. The discovery of the persiathiacins and their biosynthetic gene cluster thus provides the basis for the development of biosynthetic engineering approaches to the creation of novel (poly)glycosylated thiopeptide derivatives with enhanced pharmacological properties.

microbiology↗

bioRxiv2019

Retrograde Transport of Golgi Enzymes by GOLPH3 Across Maturing Cisternae Regulates Glycan Assembly on Sphingolipids and CellGrowth

Glycans are ubiquitous sugar polymers with major biological functions that are assembled by glyco-enzymes onto cargo molecules during their transport through the Golgi complex. How the Golgi determines glycan assembly is poorly understood. By relying on the Golgi cisternal maturation model and using the glyco-enzyme adaptor and oncoprotein GOLPH3 as a molecular tool, we define the first example of how the Golgi controls glycosylation and associated cell functions. GOLPH3, acting as a component of the cisternal maturation mechanism, selectively binds and recycles a subset of glyco-enzymes of the glycosphingolipid synthetic pathway, hinders their escape to the lysosomes and hence increases their levels through a novel lysosomal degradation-regulated mechanism. This enhances the production of specific growth-inducing glycosphingolipids and reprograms the glycosphingolipid pathway to potentiate mitogenic signaling and cell proliferation. These findings unravel unforeseen organizing principles of Golgi-dependent glycosylation and delineate a paradigm for glycan assembly by the Golgi transport mechanisms. Moreover, they indicate a new role of cisternal maturation as a regulator of glycosylation, and outline a novel mechanism of action for GOLPH3-induced proliferation.

cell biology↗

bioRxiv2018

Structure-based drug design and characterization of sulfonyl-piperazine benzothiazinone inhibitors of DprE1 from Mycobacterium tuberculosis

Macozinone (MCZ) is a tuberculosis (TB) drug candidate that specifically targets the essential flavoenzyme DprE1 thereby blocking synthesis of the cell wall precursor decaprenyl phosphoarabinose (DPA) and provoking lysis of Mycobacterium tuberculosis. As part of the MCZ back-up program we exploited structure-guided drug design to produce a new series of sulfone-containing derivatives, 2-sulphonylpiperazin 8-nitro 6-trifluoromethyl 1,3-benzothiazin-4-one, or sPBTZ. These compounds are less active than MCZ but have a better solubility profile and some derivatives display enhanced stability in microsomal assays. DprE1 was efficiently inhibited by sPBTZ and covalent adducts with the active site cysteine residue (C387) were formed. However, despite the H-bonding potential of the sulfone group no additional bonds were seen in the crystal structure of the sPBTZ-DprE1 complex with compound 11326127 as compared to MCZ. Compound 11626091, the most advanced sPBTZ, displayed good antitubercular activity in the murine model of chronic TB but was less effective than MCZ. Nonetheless, further testing of this MCZ backup compound is warranted as part of combination treatment with other TB drugs.

pharmacology and toxicology↗