Neuroleptic Properties of the Ion-Channel-Forming Peptaibol Zervamicin: Locomotor Activity and Behavioral Effects

Haloalkalitolerant Fungi from Sediments of the Big Tambukan Saline Lake (Northern Caucasus): Diversity and Antimicrobial Potential

We have performed a characterization of cultivated haloalkalitolerant fungi from the sediments of Big Tambukan Lake in order to assess their biodiversity and antimicrobial activity. This saline, slightly alkaline lake is known as a source of therapeutic sulfide mud used in sanatoria of the Caucasian Mineral Waters, Russia. Though data on bacteria and algae observed in this lake are available in the literature, data on fungi adapted to the conditions of the lake are lacking. The diversity of haloalkalitolerant fungi was low and represented by ascomycetes of the genera Acremonium, Alternaria, Aspergillus, Chordomyces, Emericellopsis, Fusarium, Gibellulopsis, Myriodontium, Penicillium, and Pseudeurotium. Most of the fungi were characterized by moderate alkaline resistance, and they tolerated NaCl concentrations up to 10% w/v. The analysis of the antimicrobial activity of fungi showed that 87.5% of all strains were active against Bacillus subtilis, and 39.6% were also determined to be effective against Escherichia coli. The majority of the strains were also active against Aspergillus niger and Candida albicans, about 66.7% and 62.5%, respectively. These studies indicate, for the first time, the presence of polyextremotolerant fungi in the sediments of Big Tambukan Lake, which probably reflects their involvement in the formation of therapeutic muds.

The Emericellipsins A-E from an Alkalophilic Fungus Emericellopsis alkalina Show Potent Activity against Multidrug-Resistant Pathogenic Fungi

Novel antimicrobial peptides with antifungal and cytotoxic activity were derived from the alkalophilic fungus Emericellopsis alkalina VKPM F1428. We previously reported that this strain produced emericellipsin A (EmiA), which has strong antifungal and cytotoxic properties. Further analyses of the metabolites obtained under a special alkaline medium resulted in the isolation of four new homologous (Emi B-E). In this work, we report the complete primary structure and detailed biological activity for the newly synthesized nonribosomal antimicrobial peptides called emericellipsins B-E. The inhibitory activity of themajor compound, EmiA, against drug-resistant pathogenic fungi was similar to that of amphotericin B (AmpB). At the same time, EmiA had no hemolytic activity towards human erythrocytes. In addition, EmiA demonstrated low cytotoxic activity towards the normal HPF line, but possessed cancer selectivity to the K-562 and HCT-116 cell lines. Emericillipsins from the alkalophilic fungus Emericellopsis alkaline are promising treatment alternatives to licensed antifungal drugs for invasive mycosis therapy, especially for multidrug-resistant aspergillosis and cryptococcosis.

Firing activity of locus coeruleus noradrenergic neurons decreases in necdin-deficient mice, an animal model of Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is a neurodevelopmental disorder characterized by multiple respiratory, cognitive, endocrine, and behavioral symptoms, such as central apnea, intellectual disabilities, exaggerated stress responses, and temper tantrums. The locus coeruleus noradrenergic system (LC-NE) modulates a diverse range of behaviors, including arousal, learning, pain modulation, and stress-induced negative affective states, which are possibly correlated with the pathogenesis of PWS phenotypes. Therefore, we evaluated the LC-NE neuronal activity of necdin-deficient mice, an animal model of PWS.

METHODS

Heterozygous necdin-deficient mice (B6.Cg-Ndntm1ky) were bred from wild-type (WT) females to generate WT (+m/+p) and heterozygotes (+m/-p) animals, which were examined of LC-NE neuronal activity, developmental reflexes, and plethysmography.

RESULTS

On slice electrophysiology, LC-NE neurons of Ndntm1ky mice with necdin deficiency showed significantly decreased spontaneous activities and impaired excitability, which was mediated by enhanced A-type voltage-dependent potassium currents. Ndntm1ky mice also exhibited the neonatal phenotypes of PWS, such as hypotonia and blunt respiratory responses to hypercapnia.

CONCLUSIONS

LC-NE neuronal firing activity decreased in necdin-deficient mice, suggesting that LC, the primary source of norepinephrine in the central nervous system, is possibly involved in PWS pathogenesis.

14-Residue peptaibol velutibol A from Trichoderma velutinum: its structural and cytotoxic evaluation

Velutibol A (1), a new 14-residue peptaibol was isolated from the Himalayan cold habitat fungus Trichoderma velutinum. The structural characterization was carried out by 1D and 2D NMR studies, and tandem mass studies, and Marfey's method aided in determining the stereochemistry of the amino acids. The CD analysis revealed folding of the peptide in a 3₁₀-helical conformation. The intramolecular H-bonding was determined by an NMR-VT experiment. Cytotoxic evaluation was carried out against a panel of cancer cell lines. The cell cycle assay was carried out on human myeloid leukaemia (HL-60) cells and revealed the formation of apoptotic bodies and DNA damage in a dose-dependent manner. Three other peptaibols namely velutibol B (2), velutibol C (3), and velutibol D (4) were also isolated in trace amounts from the psychotropic fungus and characterized through tandem mass spectroscopy and Marfey's analysis.

Velutibol A (1), a new 14-residue peptaibol isolated from the Himalayan cold habitat fungus Trichoderma velutinum.

A Novel Lipopeptaibol Emericellipsin A with Antimicrobial and Antitumor Activity Produced by the Extremophilic Fungus Emericellopsis alkalina

Soil fungi are known to contain a rich variety of defense metabolites that allow them to compete with other organisms (fungi, bacteria, nematodes, and insects) and help them occupy more preferential areas at the expense of effective antagonism. These compounds possess antibiotic activity towards a wide range of other microbes, particularly fungi that belong to different taxonomical units. These compounds include peptaibols, which are non-ribosomal synthesized polypeptides containing non-standard amino acid residues (alpha-aminoisobutyric acid mandatory) and some posttranslational modifications. We isolated a novel antibiotic peptide from the culture medium of Emericellopsis alkalina, an alkalophilic strain. This peptide, called emericellipsin A, exhibited a strong antifungal effect against the yeast Candida albicans, the mold fungus Aspergillus niger, and human pathogen clinical isolates. It also exhibited antimicrobial activity against some Gram-positive and Gram-negative bacteria. Additionally, emericellipsin A showed a significant cytotoxic effect and was highly active against Hep G2 and HeLa tumor cell lines. We used NMR spectroscopy to reveal that this peptaibol is nine amino acid residues long and contains non-standard amino acids. The mode of molecular action of emericellipsin A is most likely associated with its effects on the membranes of cells. Emericellipsin A is rather short peptaibol and could be useful for the development of antifungal, antibacterial, or anti-tumor remedies.

Unprecedented 17-residue peptaibiotics produced by marine-derived Trichoderma atroviride

In the course of investigations on marine-derived toxigenic fungi, five strains of Trichoderma atroviride were studied for their production of peptaibiotics. While these five strains were found to produce classical 19-residue peptaibols, three of them exhibited unusual peptidic sodium-adduct [M + 2 Na](2+) ion peaks at m/z between 824 and 854. The sequencing of these peptides led to two series of unprecedented 17-residue peptaibiotics based on the model Ac-XXX-Ala-Ala-XXX-XXX-Gln-Aib-Aib-Aib-Ala/Ser-Lxx-Aib-Pro-XXX-Aib-Lxx-[C(129) ]. The C-terminus of these new peptides was common to all of them, and its elemental formula C5 H9 N2 O2 was established by HR-MS. It could correspond to the cyclized form of N(δ) -hydroxyornithine which has already been observed at the C-terminus of various peptidic siderophores. The comparison of the sequences of 17- and 19-residue peptides showed similarities for positions 1-16. This observation seems to indicate a common biosynthesis pathway. Both new 17-residue peptaibiotics and 19-residue peptaibols exhibited weak in vitro cytotoxicities against KB cells.

Acrebol, a novel toxic peptaibol produced by an Acremonium exuviarum indoor isolate

AIMS

To identify a toxin and its producer isolated from woody material in a building where the occupants experienced serious ill health symptoms.

METHODS AND RESULTS

Hyphal extracts of an indoor fungus, identified as the cycloheximide-tolerant species Acremonium exuviarum, inhibited motility of boar spermatozoa (EC(50) 5 +/- 2 microg of crude solids ml(-1)) and caused cytolysis of murine neuroblastoma cells (MNA) and feline fetal lung cells (FL). The responsible substances were purified and identified as two structurally similar, heat-stable, novel, toxic peptaibols, 1726 Da and 1740 Da, respectively, with amino acid sequences of Acetyl-Phe-Iva/Val-Gln-Aib-Ile-Thr-Leu-Aib-Pro-Aib-Gln-Pro-Aib-(X-X-X)-SerOH and Acetyl-Phe-Iva/Val-Gln-Aib-Ile-Thr-Leu-Val-Pro-Aib-Gln-Pro-Aib-(X-X-X)-SerOH. Purified acrebol inhibited motility of boar sperm, depleted ATP half-content in 1 day (EC(50) of 0.1 microg ml(-1), 60 nmol l(-1)) depolarised the mitochondria after 2 days, but did not affect the cellular content in NADH. This indicates mitochondrial toxicity. Plate-grown biomass of A. exuviarum BMB4 contained 0.1-1% (w/w) of acrebol, depending on the culture medium.

CONCLUSIONS

Acrebol paralysed the energy generation of mammalian cells suggesting that mitochondria were its target of action.

SIGNIFICANCE AND IMPACT OF THE STUDY

Acremonium exuviarum, as an indoor fungus, is potentially hazardous to health because of the toxic peptaibols that it produces.

Membrane permeabilization of a mammalian neuroendocrine cell type (PC12) by the channel-forming peptides zervamicin, alamethicin, and gramicidin

Zervamicin IIB (ZER) is a 16-mer peptaibol that produces voltage-dependent conductances in artificial membranes, a property considered responsible for its antimicrobial activity to mainly Gram-positive microorganisms. In addition, ZER appears to inhibit the locomotor activity of the mouse (see elsewhere in this Issue), probably by affecting the brain. To examine whether the electrophysiological properties of the neuronal cells of the central neural system might be possibly influenced by the pore forming ZER, the present study was undertaken as a first attempt to unravel the molecular mechanism of this biological activity. To this end, membrane permeabilization of the neuron-like rat pheochromocytoma cell (PC12) by the channel-forming ZER was studied with the whole-cell patch-clamp technique, and compared with the permeabilizations of the well-known voltage-gated peptaibol alamethicin F50/5 (ALA) and the cation channel-forming peptide-antibiotic gramicidin D (GRAM). While 1 muM GRAM addition to PC12 cells kept at a membrane potential V(m)=0 mV causes an undelayed gradual increase of a leak conductance with a negative reversal potential of ca. -24 mV, ZER and ALA are ineffective at that concentration and potential. However, if ZER and ALA are added in 5-10 microM concentrations while V(m) is kept at -60 mV, they cause a sudden and strong permeabilization of the PC12 cell membrane after a delay of 1-2 min, usually leading to disintegrating morphology changes of the patched cell but not of the surrounding cells of the culture at that time scale. The zero reversal potential of the established conductance is consistent with the known aselectivity of the channels formed. This sudden permeabilization does not occur within 10-20 min at V(m)=0 mV, in accordance with the known voltage dependency of ZER and ALA channel formation in artificial lipid membranes. The permeabilizing action of these peptaibols on the culture as a whole is further supported by K(+)-release measurements from a PC12 suspension with a K(+)-selective electrode. Further analysis suggested that the permeabilizing action is associated with extra- or intracellular calcium effects, because barium inhibited the permeabilizing effects of ZER and ALA. We conclude, for the membrane of the mammalian neuron-like PC12 cell, that the permeabilizing effects of the peptides ZER and ALA are different from those of GRAM, consistent with earlier studies of these peptides in other (artificial) membrane systems. They are increased by cis-positive membrane potentials in the physiological range and may include calcium entry into the PC12 cell.