Publications by authors named "Giambattista Testolin"

4 Publications

  • Page 1 of 1

Inhibition of Type IV Secretion Activity and Growth of by Cisplatin and Other Platinum Complexes.

Front Cell Infect Microbiol 2020 18;10:602958. Epub 2020 Dec 18.

Max von Pettenkofer Institute of Hygiene and Medical Microbiology, Faculty of Medicine, LMU Munich, Munich, Germany.

Type IV secretion systems are protein secretion machineries that are frequently used by pathogenic bacteria to inject their virulence factors into target cells of their respective hosts. In the case of the human gastric pathogen , the cytotoxin-associated gene (Cag) type IV secretion system is considered a major cause for severe disease, such as gastric cancer, and thus constitutes an attractive target for specific treatment options against infections. Here, we have used a Cag type IV secretion reporter assay for screening a repurposing compound library for inhibitors targeting this system. We found that the antitumor agent cisplatin, a platinum coordination complex that kills target cells by formation of DNA crosslinks, is a potent inhibitor of the Cag type IV secretion system. Strikingly, we found that this inhibitory activity of cisplatin depends on a ligand exchange reaction which incorporates a solvent molecule (dimethylsulfoxide) into the complex, a modification which is known to be deleterious for DNA crosslinking, and for its anticancer activity. We extended our analysis to several analogous platinum complexes containing N-heterocyclic carbene, as well as DMSO or other ligands, and found varying inhibitory activities toward the Cag system which were not congruent with their DNA-binding properties, suggesting that protein interactions may cause the inhibitory effect. Inhibition experiments under varying conditions revealed effects on adherence and bacterial viability as well, and showed that the type IV secretion-inhibitory capacity of platinum complexes can be inactivated by sulfur-containing reagents and in complex bacterial growth media. Taken together, our results demonstrate DNA binding-independent inhibitory effects of cisplatin and other platinum complexes against different processes including type IV secretion.
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http://dx.doi.org/10.3389/fcimb.2020.602958DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7775389PMC
June 2021

Synthetic studies of cystobactamids as antibiotics and bacterial imaging carriers lead to compounds with high efficacy.

Chem Sci 2019 Dec 10;11(5):1316-1334. Epub 2019 Dec 10.

Department of Chemical Biology, Helmholtz Centre for Infection Research Inhoffenstrasse 7 38124 Braunschweig Germany

There is an alarming scarcity of novel chemical matter with bioactivity against multidrug-resistant Gram-negative bacterial pathogens. Cystobactamids, recently discovered natural products from myxobacteria, are an exception to this trend. Their unusual chemical structure, composed of oligomeric -aminobenzoic acid moieties, is associated with a high antibiotic activity through the inhibition of gyrase. In this study, structural determinants of cystobactamid's antibacterial potency were defined at five positions, which were varied using three different synthetic routes to the cystobactamid scaffold. The potency against could be increased ten-fold to an MIC (minimum inhibitory concentration) of 0.06 μg mL, and the previously identified spectrum gap of could be closed compared to the natural products (MIC of 0.5 μg mL). Proteolytic degradation of cystobactamids by the resistance factor AlbD was prevented by an amide-triazole replacement. Conjugation of cystobactamid's N-terminal tetrapeptide to a Bodipy moiety induced the selective localization of the fluorophore for bacterial imaging purposes. Finally, a first proof of concept was obtained in an infection mouse model, where derivative led to the reduction of bacterial loads (cfu, colony-forming units) in muscle, lung and kidneys by five orders of magnitude compared to vehicle-treated mice. These findings qualify cystobactamids as highly promising lead structures against infections caused by Gram-positive and Gram-negative bacterial pathogens.
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http://dx.doi.org/10.1039/c9sc04769gDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8148378PMC
December 2019

Adaptation of a Bacterial Multidrug Resistance System Revealed by the Structure and Function of AlbA.

J Am Chem Soc 2018 12 27;140(48):16641-16649. Epub 2018 Nov 27.

Workgroup Structural Biology of Biosynthetic Enzymes, Helmholtz Institute for Pharmaceutical Research Saarland , Helmholtz Centre for Infection Research, Saarland University , Campus Geb. E8.1 , Saarbrücken 66123 , Germany.

To combat the rise of antimicrobial resistance, the discovery of new antibiotics is paramount. Albicidin and cystobactamid are related natural product antibiotics with potent activity against Gram-positive and, crucially, Gram-negative pathogens. AlbA has been reported to neutralize albicidin by binding it with nanomolar affinity. To understand this potential resistance mechanism, we determined structures of AlbA and its complex with albicidin. The structures revealed AlbA to be comprised of two domains, each unexpectedly resembling the multiantibiotic neutralizing protein TipA. Binding of the long albicidin molecule was shared pseudosymmetrically between the two domains. The structure also revealed an unexpected chemical modification of albicidin, which we demonstrate to be promoted by AlbA, and to reduce albicidin potency; we propose a mechanism for this reaction. Overall, our findings suggest that AlbA arose through internal duplication in an ancient TipA-like gene, leading to a new binding scaffold adapted to the sequestration of long-chain antibiotics.
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http://dx.doi.org/10.1021/jacs.8b08895DOI Listing
December 2018

Discovery and Total Synthesis of Natural Cystobactamid Derivatives with Superior Activity against Gram-Negative Pathogens.

Angew Chem Int Ed Engl 2017 10 29;56(41):12760-12764. Epub 2017 Aug 29.

Abteilung Mikrobielle Naturstoffe, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Helmholtz-Zentrum für Infektionsforschung, Universitätscampus E8 1, 66123, Saarbrücken, Germany.

Antibiotic discovery and development is challenging as chemical scaffolds of synthetic origin often lack the required pharmaceutical properties, and the discovery of novel ones from natural sources is tedious. Herein, we report the discovery of new cystobactamids with a significantly improved antibacterial profile in a detailed screening of myxobacterial producer strains. Some of these new derivatives display antibacterial activities in the low-μg mL range against Gram-negative pathogens, including clinical isolates of Klebsiella oxytoca, Pseudomonas aeruginosa, and fluoroquinolone-resistant Enterobacteriaceae, which were not observed for previously reported cystobactamids. Our findings provide structure-activity relationships and show how pathogen resistance can be overcome by natural scaffold diversity. The most promising derivative 861-2 was prepared by total synthesis, enabling further chemical optimization of this privileged scaffold.
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http://dx.doi.org/10.1002/anie.201705913DOI Listing
October 2017
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