Leucinostatin Y: A Peptaibiotic Produced by the Entomoparasitic Fungus Purpureocillium lilacinum 40-H-28

Leucinostatins target Plasmodium mitochondria to block malaria transmission

BACKGROUND

Malaria remains a critical disease. Leucinostatins from the fungus Purpureocillium lilacinum inhibited the transmission of Plasmodium falciparum to mosquitoes via contact.

METHODS

Here, we modified the leucinostatin B (LB) C-terminus to make derivatives and examined their inhibition against malaria transmission to mosquitoes. Fluorescence-labeled leucinostatins were incubated with intact gametocytes and were examined under microscopy to detect the targets of leucinostatins. We also analyzed leucinostatins' general cytotoxicity and hemolysis.

RESULTS

The results showed that the derivatives with -H, -CH3, -Atto495, and -Biotin at C-terminus had EC50 of 1.5 nM, 0.2 nM, 4.2 nM, and 42 nM, respectively. Atto495 and biotin are similar in size and much bigger than -CH3 and -H. Based on reverse-phase HPLC elution time, we found that LB-Biotin had much higher hydrophobicity than the others, consistent with its lowest malaria transmission-blocking activity. Fluorescence microscopy showed that LB-Atto495 colocalized with mitochondria inside intact P. falciparum gametocytes. We found that leucinostatin A significantly inhibited the proliferation of human nucleated cells with IC50 around 47 nM and it did not lyse erythrocytes at 100 μM.

CONCLUSIONS

We conclude that the leucinostatins pass through the cytoplasmic membrane without lysing cells and interact with molecules specifically in mitochondria. Therefore, leucinostatins should be ideal inhibitors against mobile parasites, such as ookinetes and sporozoites, during malaria transmission.

Chemical Constituents of the Deep-sea Derived Fungus Purpureocillium lilacinum XIA-9

Two new sphingosine derivatives (1 and 2), two new vicinal diol analogs (3 and 4), one new diol analog (5), one new fatty acid (9), together with 19 known compounds (6-8, 10-24), were isolated from Purpureocillium lilacinum XIA-9. Their structures were determined by detailed analysis of the 1D and 2D NMR, HRESIMS, and optical rotatory data. Fusarubin 3-methyl ether (17) exhibited potent inhibition on RSL3 induced ferroptosis with the EC50 value of 0.1 μM.

Fungi-Derived Bioactive Compounds as Potential Therapeutic Agents for Pancreatic Cancer: A Systematic Review

Pancreatic cancer (PC) is one of the tumors with the lowest 5-year survival rate worldwide due to late diagnosis and lack of effective therapy. Because of this, it is necessary to discover new ways of treatment to increase the quality of life of patients. In this context, the secondary metabolites of several fungi have been shown as a possible therapeutic strategy in several types of cancer, such as colorectal cancer, being able to trigger their action through the induction of apoptosis. The objective was to perform a systematic review process to analyze the studies carried out during the last ten years using secondary metabolites derived from fungi as antitumor treatment against PC. After the search process in three databases (PubMed, SCOPUS, and Web of Science) a total of 199 articles were found, with 27 articles finally being included after screening. The results extracted from this systematic review process made it possible to determine the existence of bioactive compounds extracted from fungi that have been effective in in vitro and in vivo conditions and that may be applicable as a possible therapy to avoid drug resistance in PC, one of the major problems of this disease.

Characterization of a methyltransferase for iterative N-methylation at the leucinostatin termini in Purpureocillium lilacinum

N-methyltransferase (NMT)-catalyzed methylation at the termini of nonribosomal peptides (NRPs) has rarely been reported. Here, we discover a fungal NMT LcsG for the iterative terminal N-methylation of a family of NRPs, leucinostatins. Gene deletion results suggest that LcsG is essential for leucinostatins methylation. Results from in vitro assays and HRESI-MS-MS analysis reveal the methylation sites as NH2, NHCH3 and N(CH3)2 in the C-terminus of various leucinostatins. LcsG catalysis yields new lipopeptides, some of which demonstrate effective antibiotic properties against the human pathogen Cryptococcus neoformans and the plant pathogen Phytophthora infestans. Multiple sequence alignments and site-directed mutagenesis of LcsG indicate the presence of a highly conserved SAM-binding pocket, along with two possible active site residues (D368 and D395). Molecular dynamics simulations show that the targeted N can dock between these two residues. Thus, this study suggests a method for increasing the variety of natural bioactivity of NPRs and a possible catalytic mechanism underlying the N-methylation of NRPs.

Purpureocillium lilacinum SBF054: Endophytic in Phaseolus vulgaris, Glycine max, and Helianthus annuus; Antagonistic to Rhizoctonia solani; and Virulent to Euschistus heros

Microorganisms with multiple ecological functions can be a useful biotechnological resource in integrated pest- and disease-management programs. This work aimed to investigate the potential endophytic and virulent effects of a strain of Purpureocillium lilacinum on organic cultivation in Brazil. Specifically, the strain's ability to establish itself as an endophyte in common bean, soybean, and sunflower plants when inoculated via seed was evaluated. Furthermore, its antifungal activity against phytopathogens and its pathogenicity and virulence against insects of the order Lepidoptera, Coleoptera, and Hemiptera were evaluated. Furthermore, the strain was evaluated for its biochemical and physiological characteristics. For virulence bioassays, the experiments were conducted under a factorial scheme (2 × 3), with the following factors: (a) fungal inoculation and control without inoculum and (b) types of inocula (blastospores, aerial conidia, and metabolites). The treatments were sprayed on insect species at different stages of development. In summary, it was found that the SBF054 strain endophytically colonized the common bean, with partial recovery from the root tissues of soybean and sunflower plants, 30 days after inoculation; suppressed 86% of Rhizoctonia solani mycelial growth in an in vitro assay; and controlled eggs, nymphs, and Euschistus heros adults. These multifunctional abilities are mainly attributed to the strain's mechanisms of producing metabolites, such as organic acids, soluble nutrients, and hydrolytic enzymes.

Revealing the Anticancer Mechanism of Cephaibol A, a Peptaibol Isolated from Acremonium tubakii BMC-58, Triggering Apoptosis via the Mitochondrial Pathway in Human Breast Cancer Cells

Cephaibol A was isolated from a freshwater fungus Acremonium tubakii BMC-58 extract which composed of 16 amino acids and featuring multiple α-aminoisobutyric acid. We investigated the cytotoxicity of cephaibol A on MDA-MB-231 cells to elucidate its potential antitumor activity and mechanism. The study found that cephaibol A concentration-dependently blocked the cell cycle in S phase and inhibited cell proliferation. Meanwhile, cephaibol A could reduce the migration and invasion abilities of MDA-MB-231 cells. Further studies proved that cephaibol A caused mitochondrial dysfunction and increased reactive oxygen species (ROS) accumulation. Mitochondrial membrane potential (ΔΨm) assay suggested that cephaibol A induced apoptosis by affecting Bcl-2, Bax and cytochrome c levels, thus decreasing ΔΨm and activating the caspase cascade reaction. Moreover, cephaibol A significantly inhibited tumor growth and improved survival rates in the MDA-MB-231 cell mice model. These findings established cephaibol A as a potential antitumor agent that inhibited tumor cell proliferation in vitro and in vivo by affecting mitochondrial dysfunction and inducing apoptosis in MDA-MB-231 cells through structural damage.

The Anti-Tubercular Aminolipopeptide Trichoderin A Displays Selective Toxicity against Human Pancreatic Ductal Adenocarcinoma Cells Cultured under Glucose Starvation

Pancreatic ductal adenocarcinoma remains a highly debilitating condition with no effective disease-modifying interventions. In our search for natural products with promising anticancer activity, we identified the aminolipopeptide trichoderin A as a potential candidate. While it was initially isolated as an antitubercular peptide, we provide evidence that it is also selectively toxic against BxPC-3 and PANC-1 human pancreatic ductal adenocarcinoma cells cultured under glucose deprivation. This has critical implications for the pancreatic ductal adenocarcinoma, which is characterized by nutrient deprivation due to its hypovascularized network. We have also successfully simplified the trichoderin A peptide backbone, allowing greater accessibility to the peptide for further biological testing. In addition, we also conducted a preliminary investigation into the role of peptide lipidation at the N-terminus. This showed that analogues with longer fatty acyl chains exhibited superior cytotoxicity than those with shorter acyl chains. Further structural optimization of trichoderin A is anticipated to improve its biological activity, whilst ongoing mechanistic studies to elucidate its intracellular mechanism of action are conducted in parallel.

Cytotoxic hexadepsipeptides and anti-coronaviral 4-hydroxy-2-pyridones from an endophytic Fusarium sp

Three new hexadepsipeptides (1-3), along with beauvericin (4), beauvericin D (5), and four 4-hydroxy-2-pyridone derivatives (6-9) were isolated from the endophytic fungus Fusarium sp. CPCC 400857 that derived from the stem of tea plant. Their structures were determined by extensive 1D and 2D NMR, and HRESIMS analyses. The absolute configuration of hexadepsipeptides were elucidated by the advanced Marfey's method and chiral HPLC analysis. Compounds 4, and 7-9 displayed the cytotoxicity against human pancreatic cancer cell line, AsPC-1 with IC₅₀ values ranging from 3.45 to 29.69 μM, and 7 and 8 also showed the antiviral activity against the coronavirus (HCoV-OC43) with IC₅₀ values of 13.33 and 6.65 μM, respectively.

Gut mycobiota dysbiosis in drug-naïve, first-episode schizophrenia

Bacterial dysbiosis has been demonstrated in patients with schizophrenia (SCH). The aim of the present study was to investigate alterations in mycobiota composition and fungi-bacteria correlation network in drug-naïve, first episode SCH. We recruited 205 SCH patients and 125 healthy controls (HCs), whose gut bacterial and fungal compositions were characterized by 16S and 18S ribosomal RNA gene amplicon sequencing, respectively. Fungal-bacterial relative correlation network analysis was performed using the Spearman's test and distance correlation. We also computed relative networks connectedness, which represents the ratio of significant interactions (edges) and taxa (nodes) in the network. SCH patients showed lower fungal α-diversity compared with that of HCs. Furthermore, we identified 29 differential fungal markers at multiple taxonomies between SCH patients and HCs. SCH patients also showed a significantly lower fungi-to-bacteria α-diversity ratio compared with that of HCs (p = 1.81 × 10^-8). In risk prediction models, we observed that combining bacterial and fungal markers achieved higher accuracy than that of bacterial markers alone (AUC = 0.847 vs AUC = 0.739; p = 0.043). Fungal-bacterial correlation network was denser in HCs than in SCH patients and was characterized by a high number of neighbors (p < 0.05). In addition, an increased abundance of Purpureocillium was associated with more severe psychiatric symptoms and poorer cognitive function in SCH patients (p < 0.05). Our study demonstrated a disrupted and weakened fungi-bacteria network in SCH patients, which might be associated with their clinical manifestations. Future research on fungal-bacterial correlation network is warranted to advance our understanding about the role of mycobiota in the etiology of SCH and to explore novel intervention approaches.

Tolypocladamide H and the Proposed Tolypocladamide NRPS in Tolypocladium Species

The genome of entomopathogenic fungus Tolypocladium inflatum Gams encodes 43 putative biosynthetic gene clusters for specialized metabolites, although genotype-phenotype linkages have been reported only for the cyclosporins and fumonisins. T. inflatum was cultured in defined minimal media, supplemented with or without one of nine different amino acids. Acquisition of LC-MS/MS data for molecular networking and manual analysis facilitated annotation of putative known and unknown metabolites. These data led us to target a family of peptaibols and guided the isolation and purification of tolypocladamide H (1), which showed modest antibacterial activity and toxicity to mammalian cells at micromolar concentrations. HRMS/MS, NMR, and advanced Marfey's analysis were used to assign the structure of 1 as a peptaibol containing 4-[(E)-2-butenyl]-4-methyl-l-threonine (Bmt), a hallmark structural motif of the cyclosporins. LC-MS detection of homologous tolypocladamide metabolites and phylogenomic analyses of peptaibol biosynthetic genes in other cultured Tolypocladium species allowed assignment of a putative tolypocladamide nonribosomal peptide synthetase gene.

Secondary Metabolites of Purpureocilliumlilacinum

Fungi can synthesize a wealth of secondary metabolites, which are widely used in the exploration of lead compounds of pharmaceutical or agricultural importance. Beauveria, Metarhizium, and Cordyceps are the most extensively studied fungi in which a large number of biologically active metabolites have been identified. However, relatively little attention has been paid to Purpureocillium lilacinum. P. lilacinum are soil-habituated fungi that are widely distributed in nature and are very important biocontrol fungi in agriculture, providing good biological control of plant parasitic nematodes and having a significant effect on Aphidoidea, Tetranychus cinnbarinus, and Aleyrodidae. At the same time, it produces secondary metabolites with various biological activities such as anticancer, antimicrobial, and insecticidal. This review attempts to provide a comprehensive overview of the secondary metabolites of P. lilacinum, with emphasis on the chemical diversity and biological activity of these secondary metabolites and the biosynthetic pathways, and gives new insight into the secondary metabolites of medical and entomogenous fungi, which is expected to provide a reference for the development of medicine and agrochemicals in the future.

Rare Glutamic Acid Methyl Ester Peptaibols from Sepedonium ampullosporum Damon KSH 534 Exhibit Promising Antifungal and Anticancer Activity

Fungal species of genus Sepedonium are rich sources of diverse secondary metabolites (e.g., alkaloids, peptaibols), which exhibit variable biological activities. Herein, two new peptaibols, named ampullosporin F (1) and ampullosporin G (2), together with five known compounds, ampullosporin A (3), peptaibolin (4), chrysosporide (5), c(Trp-Ser) (6) and c(Trp-Ala) (7), have been isolated from the culture of Sepedonium ampullosporum Damon strain KSH534. The structures of 1 and 2 were elucidated based on ESI-HRMSⁿ experiments and intense 1D and 2D NMR analyses. The sequence of ampullosporin F (1) was determined to be Ac-Trp¹-Ala²-Aib³-Aib⁴-Leu⁵-Aib⁶-Gln⁷-Aib⁸-Aib⁹-Aib¹⁰-GluOMe¹¹-Leu¹²-Aib¹³-Gln¹⁴-Leuol¹⁵, while ampullosporin G (2) differs from 1 by exchanging the position of Gln⁷ with GluOMe¹¹. Furthermore, the total synthesis of 1 and 2 was carried out on solid-phase to confirm the absolute configuration of all chiral amino acids as L. In addition, ampullosporin F (1) and G (2) showed significant antifungal activity against B. cinerea and P. infestans, but were inactive against S. tritici. Cell viability assays using human prostate (PC-3) and colorectal (HT-29) cancer cells confirmed potent anticancer activities of 1 and 2. Furthermore, a molecular docking study was performed in silico as an attempt to explain the structure-activity correlation of the characteristic ampullosporins (1–3).

The therapeutic potential of mitochondrial toxins

When screening active compounds by phenotypic assays, we often encounter mitochondrial toxins, which are compounds that can affect mitochondrial functions. In normal cells, these toxins may have relatively low toxicity but can nonetheless show measurable effects even at low concentrations. On the other hand, in animals, mitochondrial toxins can exert severe toxicity. Mitochondrial toxins that act as inhibitors of respiratory chain complexes in oxidative phosphorylation (OXPHOS) are typically avoided during drug discovery efforts, as such compounds can directly promote lethal inhibition of pulmonary respiration. However, mitochondrial toxins could in fact have beneficial therapeutic effects. Anti-cancer strategies that target mitochondrial functions, particularly OXPHOS, have received increasing attention in recent years. In this review article we examine the significance of OXPHOS inhibitors as anti-cancer drug candidates and discuss compounds having microbial origins.

Secondary metabolites from hypocrealean entomopathogenic fungi: genomics as a tool to elucidate the encoded parvome

Covering: 2014 up to the third quarter of 2019 Hypocrealean entomopathogenic fungi (HEF) produce a large variety of secondary metabolites (SMs) that are prominent virulence factors or mediate various interactions in the native niches of these organisms. Many of these SMs show insecticidal, immune system modulatory, antimicrobial, cytotoxic and other bioactivities of clinical or agricultural significance. Recent advances in whole genome sequencing technologies and bioinformatics have revealed many biosynthetic gene clusters (BGCs) potentially involved in SM production in HEF. Some of these BGCs are now well characterized, with the structures of the cognate product congeners elucidated, and the proposed biosynthetic functions of key enzymes validated. However, the vast majority of HEF BGCs are still not linked to SM products ("orphan" BGCs), including many clusters that are not expressed (silent) under routine laboratory conditions. Thus, investigations into the encoded parvome (the secondary metabolome predicted from the genome) of HEF allows the discovery of BGCs for known SMs; uncovers novel metabolites based on the BGCs; and catalogues the predicted SM biosynthetic potential of these fungi. Herein, we summarize new developments of the field, and survey the polyketide, nonribosomal peptide, terpenoid and hybrid SM BGCs encoded in the currently available 40 HEF genome sequences. Studying the encoded parvome of HEF will increase our understanding of the multifaceted roles that SMs play in biotic and abiotic interactions and will also reveal biologically active SMs that can be exploited for the discovery of human and veterinary drugs or crop protection agents.

Antiprotozoal Structure-Activity Relationships of Synthetic Leucinostatin Derivatives and Elucidation of their Mode of Action

Leucinostatin A is one of the most potent antiprotozoal compounds ever described, but little was known on structure-activity relationships (SAR). We used Trypanosoma brucei as a protozoal model organism to test synthetically modified derivatives, resulting in simplified but equally active compounds 2 (ZHAWOC6025) and 4 (ZHAWOC6027), which were subsequently modified in all regions of the molecule to gain an in-depth SAR understanding. The antiprotozoal SAR matched SAR in phospholipid liposomes, where membrane integrity, leaking, and dynamics were studied. The mode of action is discussed based on a structure-activity analysis of derivatives in efficacy, ultrastructural studies in T. brucei, and artificial membrane models, mimicking membrane stability and membrane potential. The main site of antiprotozoal action of natural and synthetic leucinostatins lies in the destabilization of the inner mitochondrial membrane, as demonstrated by ultrastructural analysis, electron microscopy and mitochondrial staining. Long-time sublethal exposure of T. brucei (200 passages) and siRNA screening of 12'000 mutants showed no signs of resistance development to the synthetic derivatives.

Organic Antifungal Drugs and Targets of Their Action

In recent decades, there has been a significant increase in the number of fungal diseases. This is due to a wide spectrum of action, immunosuppressants and other group drugs. In terms of frequency, rapid spread and globality, fungal infections are approaching acute respiratory infections. Antimycotics are medicinal substances endorsed with fungicidal or fungistatic properties. For the treatment of fungal diseases, several groups of compounds are used that differ in their origin (natural or synthetic), molecular targets and mechanism of action, antifungal effect (fungicidal or fungistatic), indications for use (local or systemic infections), and methods of administration (parenteral, oral, outdoor). Several efforts have been made by various medicinal chemists around the world for the development of antifungal drugs with high efficacy with the least toxicity and maximum selectivity in the area of antifungal chemotherapy. The pharmacokinetic properties of the new antimycotics are also important: the ability to penetrate biological barriers, be absorbed and distributed in tissues and organs, get accumulated in tissues affected by micromycetes, undergo drug metabolism in the intestinal microflora and human organs, and in the kinetics of excretion from the body. There are several ways to search for new effective antimycotics: - Obtaining new derivatives of the already used classes of antimycotics with improved activity properties. - Screening of new chemical classes of synthetic antimycotic compounds. - Screening of natural compounds. - Identification of new unique molecular targets in the fungal cell. - Development of new compositions and dosage forms with effective delivery vehicles. The methods of informatics, bioinformatics, genomics and proteomics were extensively investigated for the development of new antimycotics. These techniques were employed in finding and identification of new molecular proteins in a fungal cell; in the determination of the selectivity of drugprotein interactions, evaluation of drug-drug interactions and synergism of drugs; determination of the structure-activity relationship (SAR) studies; determination of the molecular design of the most active, selective and safer drugs for the humans, animals and plants. In medical applications, the methods of information analysis and pharmacogenomics allow taking into account the individual phenotype of the patient, the level of expression of the targets of antifungal drugs when choosing antifungal agents and their dosage. This review article incorporates some of the most significant studies covering the basic structures and approaches for the synthesis of antifungal drugs and the directions for their further development.

Action mechanisms and biocontrol of Purpureocillium lilacinum against green mould caused by Penicillium digitatum in orange fruit

AIMS

The present study evaluated, for the first time, the inhibitory effects of the filtrate of Purpureocillium lilacinum against Penicillium digitatum.

METHODS AND RESULTS

No direct contact between P. lilacinum and P. digitatum was observed during the dual culture test and the inhibition zone was 6·1 mm. The filtrate of P. lilacinum completely inhibited P. digitatum growth and spore germination at the concentration of 64%. The filtrate increased the permeability of the cell membrane and the content of MDA in P. digitatum. The ergosterol content in P. digitatum was strongly inhibited at 32% by 81·1%. The green mould incidence and severity in filtrate-treated fruit at 64% were 71·7 and 80·7% lower than in the control, respectively. The filtrate enhanced the activity of PAL, PPO and POD enzymes in orange fruit. The POD and PAL gene expression levels were significantly upregulated in the fruit treated with the filtrate.

CONCLUSIONS

This study indicated that the antifungal mechanism of P. lilacinum filtrate against P. digitatum is mainly by the damage of the fungal cell membrane and its components.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work provides the pioneer evidence on the application of P. lilacinum filtrate as a novel biocontrol agent for orange green mould.

Leucinostatins from Ophiocordyceps spp. and Purpureocillium spp. Demonstrate Selective Antiproliferative Effects in Cells Representing the Luminal Androgen Receptor Subtype of Triple Negative Breast Cancer

The structures of four leucinostatin analogues (1-4) from Ophiocordyceps spp. and Purpureocillium spp. were determined together with six known leucinostatins [leucinostatins B (5), A (6), B2 (7), A2 (8), F (9), and D (10)]. The structures of the metabolites were established using a combination of analytical methods including HRESIMS and MS/MS experiments, 1D and 2D NMR spectroscopy, chiral HPLC, and advanced Marfey's analysis of the acid hydrolysate, as well as additional empirical and chemical methods. Compounds 1-10 were evaluated for their biological effects on triple negative breast cancer (TNBC) cells. Leucinostatins 1-10 showed selective cytostatic activities in MDA-MB-453 and SUM185PE cells representing the luminal androgen receptor subtype of TNBC. This selective activity motivated further investigation into the mechanism of action of leucinostatin B (5). The results demonstrate that this peptidic fungal metabolite rapidly inhibits mTORC1 signaling in leucinostatin-sensitive TNBC cell lines, but not in leucinostatin-resistant cells. Leucinostatins have been shown to repress mitochondrial respiration through inhibition of the ATP synthase, and we demonstrated that both the mTORC1 signaling and LAR-selective activities of 5 were recapitulated by oligomycin. Thus, inhibition of the ATP synthase with either leucinostatin B or oligomycin is sufficient to selectively impede mTORC1 signaling and inhibit the growth of LAR-subtype cells.

New Peptaibiotics and a Cyclodepsipeptide from Ijuhya vitellina: Isolation, Identification, Cytotoxic and Nematicidal Activities

Fungal associations with nematodes have attracted scientific attention because of the need to develop new biocontrol agents. In this context, Ijuhya vitellina, an antagonistic fungus previously isolated from the plant parasitic cyst nematode Heterodera filipjevi, was selected to carry out an in-depth metabolomic study for its active metabolites. Herein, three new nonapeptide peptaibols with leucinostatin based sequences were isolated and identified by 1, 2D NMR, and HR-ESI-MS-MS. The absolute configuration was assigned based on Marfay’s analysis and Mosher ester formation. The new leucinostatins manifested moderate nematicidal effect against the plant pathogenic nematode Pratylenchus penetrans with LD₉₀ values ranging from 5 to 7 µg/mL. Furthermore, a cyclodepsipeptide, named arthrichitin D, with five amino acid residues attached to a 3-hydroxy-2,4-dimethylhexadeca-4,6-dienoic fatty acid chain was discovered and showed weak nematicidal effect against Caenorhabditis elegans. Chaetoglobosin B and its 19-O-acetyl derivative were also obtained as minor metabolites, and the activity of chaetoglobosin B on the actin cytoskeleton of mammalian cells was assessed.

A diastereoselective approach to amino alcohols and application for divergent synthesis of dolastatin 10

A diastereoselective approach to obtain amino alcohols through SmI₂-induced radical addition and divergent synthesis of dolastatin 10 are described.