Gallinamide A, originally isolated with a modest antimalarial activity, was subsequently reisolated and characterized as a potent, selective, and irreversible inhibitor of the human cysteine protease ...cathepsin L. Molecular docking identified potential modifications to improve binding, which were synthesized as a suite of analogs. Resultingly, this current study produced the most potent gallinamide analog yet tested against cathepsin L (10, K i = 0.0937 ± 0.01 nM and k inact/K i = 8 730 000). From a protein structure and substrate preference perspective, cruzain, an essential Trypanosoma cruzi cysteine protease, is highly homologous. Our investigations revealed that gallinamide and its analogs potently inhibit cruzain and are exquisitely toxic toward T. cruzi in the intracellular amastigote stage. The most active compound, 5, had an IC50 = 5.1 ± 1.4 nM, but was relatively inactive to both the epimastigote (insect stage) and the host cell, and thus represents a new candidate for the treatment of Chagas disease.
Bacteria use small molecules to impose strict regulation over the acquisition, uptake, and sequestration of transition metal ions. Low-abundance nutrient metals, such as Fe(III), need to be ...scavenged from the environment by high-affinity chelating molecules called siderophores. Conversely, metal ions that become toxic at high concentrations need to be sequestered and detoxified. Often, bacteria produce a suite of compounds that bind various metal ions at different affinities in order to maintain homeostasis. Turnerbactin, a triscatecholate siderophore isolated from the intracellular shipworm symbiont Teredinibacter turnerae T7901, is responsible for iron regulation and uptake. Herein, another series of compounds are described that complex with iron, copper, and molybdenum in solution. Teredinibactins belong to a class of metal-binding molecules that utilize a phenolate-thiazoline moiety in the coordination of metal ions. In contrast to other compounds in this class, such as yersiniabactin, the phenyl ring is decorated with a 2,4-dihydroxy-3-halo substitution pattern. UV–vis absorption spectroscopy based titration experiments with CuCl2 show the formation of an intermediate complex at substoichiometric concentrations and conversion to a copper-bound complex at 1:1 molar equiv.
Integrating LC-MS/MS molecular networking and bioassay-guided fractionation enabled the targeted isolation of a new and bioactive cyclic octapeptide, samoamide A (1), from a sample of cf. Symploca ...sp. collected in American Samoa. The structure of 1 was established by detailed 1D and 2D NMR experiments, HRESIMS data, and chemical degradation/chromatographic (e.g., Marfey’s analysis) studies. Pure compound 1 was shown to have in vitro cytotoxic activity against several human cancer cell lines in both traditional cell culture and zone inhibition bioassays. Although there was no particular selectivity between the cell lines tested for samoamide A, the most potent activity was observed against H460 human non-small-cell lung cancer cells (IC50 = 1.1 μM). Molecular modeling studies suggested that one possible mechanism of action for 1 is the inhibition of the enzyme dipeptidyl peptidase (CD26, DPP4) at a reported allosteric binding site, which could lead to many downstream pharmacological effects. However, this interaction was moderate when tested in vitro at up to 10 μM and only resulted in about 16% peptidase inhibition. Combining bioassay screening with the cheminformatics strategy of LC-MS/MS molecular networking as a discovery tool expedited the targeted isolation of a natural product possessing both a novel chemical structure and a desired biological activity.
Teredinibacter turnerae is an intracellular bacterial symbiont in the gills of wood-eating shipworms, where it is proposed to use antibiotics to defend itself and its animal host. Several ...biosynthetic gene clusters are conserved in T. turnerae and their host shipworms around the world, implying that they encode defensive compounds. Here, we describe turnercyclamycins, lipopeptide antibiotics encoded in the genomes of all sequenced T. turnerae strains. Turnercyclamycins are bactericidal against challenging Gram-negative pathogens, including colistin-resistant Acinetobacter baumannii. Phenotypic screening identified the outer membrane as the likely target. Turnercyclamycins and colistin operate by similar cellular, although not necessarily molecular, mechanisms, but turnercyclamycins kill colistin-resistant A. baumannii, potentially filling an urgent clinical need. Thus, by exploring environments that select for the properties we require, we harvested the fruits of evolution to discover compounds with potential to target unmet health needs. Investigating the symbionts of shipworms is a powerful example of this principle.
Display omitted
•Microbial competition in a symbiosis leading to antibiotics•Group of lipopeptide antibiotics that targets drug-resistant Acinetobacter
The symbiotic bacteria associated with marine shipworms are prolific producers of bioactive metabolites. Miller et al. use an ecology-guided approach to isolate the turnercyclamycins, proposed to be important for this association. Turnercyclamycins are described as a group of lipopeptide antibiotics with selective activity against Gram-negative pathogens, including drug-resistant Acinetobacter.
The emergence of antibiotic resistance necessitates not only the identification of new compounds with antimicrobial properties, but also new strategies and combination therapies to circumvent this ...growing problem. Here, we report synergistic activity against methicillin-resistant Staphylococcus aureus (MRSA) of the β-lactam antibiotic oxacillin combined with 7,8-dideoxygriseorhodin C in vitro. Ongoing efforts to identify antibiotics from marine mollusk-associated bacteria resulted in the isolation of 7,8-dideoxygriseorhodin C from a Streptomyces sp. strain cultivated from a marine gastropod tissue homogenate. Despite the long history of 7,8-dideoxygriseorhodin C in the literature, the absolute configuration has never been previously reported. A comparison of measured and calculated ECD spectra resolved the configuration of the spiroketal carbon C6, and 2D ROESY NMR spectroscopy established the absolute configuration as 6s,6aS. The compound is selective against Gram-positive bacteria including MRSA and Enterococcus faecium with an MIC range of 0.125-0.5 μg ml
. Moreover, the compound synergizes with oxacillin against MRSA as observed in the antimicrobial microdilution and time-kill assays. Simultaneous treatment of the compound with oxacillin resulted in an approximately tenfold decrease in MIC with a combination index of <0.5, indicating synergistic anti-MRSA activity.
Abstract Background The high prevalence and severity of methamphetamine (MA) abuse demands greater neurobiological understanding of its etiology. Methods Here, we conducted immunoblotting and in vivo ...microdialysis procedures in Methamphetamine High/Low Drinking (MAH/LDR) mice, as well as in isogenic C57BL/6J mice that varied in their MA-preference/taking, to examine the glutamate underpinnings of MA abuse vulnerability. Neuropharmacological and Homer2 knock-down approaches were also employed in C57BL/6J mice to confirm the role for nucleus accumbens glutamate/Homer2 expression in MA preference/aversion. Results We identified a hyper-glutamatergic state within the nucleus accumbens (NAC) as a biochemical trait corresponding with both genetic and idiopathic vulnerability for high MA-preference and -taking. We also confirmed that subchronic, subtoxic MA experience elicits a hyper-glutamatergic state within the NAC during protracted withdrawal, characterized by elevated mGlu1/5 receptor function and Homer2 receptor-scaffolding protein expression. A high MA-preferring phenotype was recapitulated by elevating endogenous glutamate within the NAC shell of mice and we reversed MA-preference/taking by lowering endogenous glutamate and/or Homer2 expression within this subregion. Conclusions Our data point to an idiopathic, genetic or drug-induced hyper-glutamatergic state within the NAC as a mediator of MA addiction vulnerability.
Background
Alcohol increases the expression of Group 1 metabotropic glutamate receptors (mGluRs) and their associated scaffolding protein Homer2 and stimulates phosphatidylinositol 3‐kinase (PI3K) ...within the nucleus accumbens (NAC). Moreover, functional studies suggest that NAC Group 1 mGluR/Homer2/PI3K signaling may be a potential target for pharmacotherapeutic intervention in alcoholism.
Methods
Immunoblotting was conducted to examine the effects of alcohol consumption under drinking‐in‐the‐dark (DID) procedures on Group 1 mGluR‐associated proteins in C57BL/6J (B6) mice. Follow‐up behavioral studies examined the importance of Group 1 mGluR/Homer2/PI3K signaling within the NAC shell for limited‐access alcohol drinking. Finally, immunoblotting examined whether the NAC expression of Group 1 mGluR‐associated proteins is a genetic correlate of high alcohol drinking using a selectively bred high DID (HDID‐1) mouse line.
Results
Limited‐access alcohol drinking under DID procedures up‐regulated NAC shell Homer2 levels, concomitant with increases in mGluR5 and NR2B. Intra‐NAC shell blockade of mGluR5, Homer2, or PI3K signaling, as well as transgenic disruption of the Homer binding site on mGluR5, decreased alcohol consumption in B6 mice. Moreover, transgenic disruption of the Homer binding site on mGluR5 and Homer2 deletion both prevented the attenuating effect of mGluR5 and PI3K blockade upon intake. Finally, the basal NAC shell protein expression of mGluR1 and Homer2 was increased in offspring of HDID‐1 animals.
Conclusions
Taken together, these data further implicate Group 1 mGluR signaling through Homer2 within the NAC in excessive alcohol consumption.
Bacterial resistance to antibiotics is a crisis.
is among the CDC urgent threat pathogens in part for this reason. Lipopeptides known as turnercyclamycins are produced by symbiotic bacteria that ...normally live in marine mollusks, where they may be involved in shaping their symbiotic niche. Turnercyclamycins killed Gram-negative pathogens including drug-resistant
, but how do the mechanisms of resistance compare to other lipopeptide drugs? Here, we define resistance from a truncation of MlaA, a protein involved in regulating bacterial membrane phospholipids. Intriguingly, this resistance mechanism only affected one turnercyclamycin variant, which differed only in two atoms in the lipid tail of the compounds. We could not obtain significant resistance to the second turnercyclamycin variant, which was also effective in an infection model. This study reveals an unexpected subtlety in resistance to lipopeptide antibiotics, which may be useful in the design and development of antibiotics to combat drug resistance.
Three new pyoluteorin analogues, mindapyrroles A–C (1-3), were purified from Pseudomonas aeruginosa strain 1682U.R.0a.27, a gill-associated bacterium isolated from the tissue homogenate of the giant ...shipworm Kuphus polythalamius. Mindapyrroles B and C inhibit the growth of multiple pathogenic bacteria, with mindapyrrole B (2) showing the most potent antimicrobial activity and widest selectivity index over mammalian cells. Preliminary structure–activity relationship analysis showed that dimerization of the pyoluteorin moiety through a C–C linkage is detrimental to the antimicrobial activity, but addition of an aerugine unit in the methylene bridge is favorable for both the antimicrobial activity and selectivity index.
The bioactivity-guided purification of the culture broth of the shipworm endosymbiont
strain 991H.S.0a.06 yielded a new fatty acid, turneroic acid (
), and two previously described oxylipins (
-
). ...Turneroic acid (
) is an 18-carbon fatty acid decorated by a hydroxy group and an epoxide ring. Compounds
-
inhibited bacterial biofilm formation in
, while only
showed antimicrobial activity against planktonic
.
. Comparison of the bioactivity of
-
with structurally related compounds indicated the importance of the epoxide moiety for selective and potent biofilm inhibition.
PDF
