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Rainsford P, Rylandsholm FG, Jakubec M, Silk M, Juskewitz E, Ericson JU, Svendsen JS, Engh RA, Isaksson J. Label-free measurement of antimicrobial peptide interactions with lipid vesicles and nanodiscs using microscale thermophoresis. Sci Rep 2023; 13:12619. [PMID: 37537266 PMCID: PMC10400562 DOI: 10.1038/s41598-023-39785-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 07/31/2023] [Indexed: 08/05/2023] Open
Abstract
One strategy to combat antimicrobial resistance is the discovery of new classes of antibiotics. Most antibiotics will at some point interact with the bacterial membrane to either interfere with its integrity or to cross it. Reliable and efficient tools for determining the dissociation constant for membrane binding (KD) and the partitioning coefficient between the aqueous- and membrane phases (KP) are therefore important tools for discovering and optimizing antimicrobial hits. Here we demonstrate that microscale thermophoresis (MST) can be used for label-free measurement of KD by utilising the intrinsic fluorescence of tryptophan and thereby removing the need for chromophore labelling. As proof of principle, we have used the method to measure the binding of a set of small cyclic AMPs to large unilamellar vesicles (LUVs) and two types of lipid nanodiscs assembled by styrene maleic acid (SMA) and quaternary ammonium SMA (SMA-QA). The measured KD values correlate well with the corresponding measurements using surface plasmon resonance (SPR), also broadly reflecting the tested AMPs' minimal inhibition concentration (MIC) towards S. aureus and E. coli. We conclude that MST is a promising method for fast and cost-efficient detection of peptide-lipid interactions or mapping of sample conditions in preparation for more advanced studies that rely on expensive sample preparation, labelling and/or instrument time.
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Affiliation(s)
- Philip Rainsford
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019, Tromsø, Norway
| | - Fredrik G Rylandsholm
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019, Tromsø, Norway
| | - Martin Jakubec
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019, Tromsø, Norway
| | - Mitchell Silk
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019, Tromsø, Norway
| | - Eric Juskewitz
- Research Group for Host Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT the Arctic University of Norway, 9019, Tromsø, Norway
| | - Johanna U Ericson
- Research Group for Host Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT the Arctic University of Norway, 9019, Tromsø, Norway
| | - John-Sigurd Svendsen
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019, Tromsø, Norway
| | - Richard A Engh
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019, Tromsø, Norway
| | - Johan Isaksson
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019, Tromsø, Norway.
- Natural Products and Medicinal Chemistry, Department of Pharmacy, Faculty of Health Sciences, UiT the Arctic University of Norway, 9037, Tromsø, Norway.
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Juskewitz E, Mishchenko E, Dubey VK, Jenssen M, Jakubec M, Rainsford P, Isaksson J, Andersen JH, Ericson JU. Lulworthinone: In Vitro Mode of Action Investigation of an Antibacterial Dimeric Naphthopyrone Isolated from a Marine Fungus. Mar Drugs 2022; 20:md20050277. [PMID: 35621928 PMCID: PMC9147123 DOI: 10.3390/md20050277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 04/13/2022] [Accepted: 04/16/2022] [Indexed: 01/27/2023] Open
Abstract
Treatment options for infections caused by antimicrobial-resistant bacteria are rendered ineffective, and drug alternatives are needed—either from new chemical classes or drugs with new modes of action. Historically, natural products have been important contributors to drug discovery. In a recent study, the dimeric naphthopyrone lulworthinone produced by an obligate marine fungus in the family Lulworthiaceae was discovered. The observed potent antibacterial activity against Gram-positive bacteria, including several clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates, prompted this follow-up mode of action investigation. This paper aimed to characterize the antibacterial mode of action (MOA) of lulworthinone by combining in vitro assays, NMR experiments and microscopy. The results point to a MOA targeting the bacterial membrane, leading to improper cell division. Treatment with lulworthinone induced an upregulation of genes responding to cell envelope stress in Bacillus subtilis. Analysis of the membrane integrity and membrane potential indicated that lulworthinone targets the bacterial membrane without destroying it. This was supported by NMR experiments using artificial lipid bilayers. Fluorescence microscopy revealed that lulworthinone affects cell morphology and impedes the localization of the cell division protein FtsZ. Surface plasmon resonance and dynamic light scattering assays showed that this activity is linked with the compound‘s ability to form colloidal aggregates. Antibacterial agents acting at cell membranes are of special interest, as the development of bacterial resistance to such compounds is deemed more difficult to occur.
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Affiliation(s)
- Eric Juskewitz
- Research Group for Host Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (E.M.); (V.K.D.)
- Correspondence: (E.J.); (J.U.E.)
| | - Ekaterina Mishchenko
- Research Group for Host Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (E.M.); (V.K.D.)
| | - Vishesh K. Dubey
- Research Group for Host Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (E.M.); (V.K.D.)
| | - Marte Jenssen
- Marbio, The Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (M.J.); (J.H.A.)
| | - Martin Jakubec
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (M.J.); (P.R.); (J.I.)
| | - Philip Rainsford
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (M.J.); (P.R.); (J.I.)
| | - Johan Isaksson
- Department of Chemistry, Faculty of Science and Technology, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (M.J.); (P.R.); (J.I.)
| | - Jeanette H. Andersen
- Marbio, The Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (M.J.); (J.H.A.)
| | - Johanna U. Ericson
- Research Group for Host Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, UiT the Arctic University of Norway, 9019 Tromsø, Norway; (E.M.); (V.K.D.)
- Correspondence: (E.J.); (J.U.E.)
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