In silico prospection of receptors associated with the biological activity of U1-SCTRX-lg1a: an antimicrobial peptide isolated from the venom of Loxosceles gaucho.

The emergence of antibiotic-resistant pathogens generates impairment to human health. U1-SCTRX-lg1a is a peptide isolated from a phospholipase D extracted from the spider venom of Loxosceles gaucho with antimicrobial activity against Gram-negative bacteria (between 1.15 and 4.6 µM). The aim of this study was to suggest potential receptors associated with the antimicrobial activity of U1-SCTRX-lg1a using in silico bioinformatics tools. The search for potential targets of U1-SCRTX-lg1a was performed using the PharmMapper server. Molecular docking between U1-SCRTX-lg1a and the receptor was performed using PatchDock software. The prediction of ligand sites for each receptor was conducted using the PDBSum server. Chimera 1.6 software was used to perform molecular dynamics simulations only for the best dock score receptor. In addition, U1-SCRTX-lg1a and native ligand interactions were compared using AutoDock Vina software. Finally, predicted interactions were compared with the ligand site previously described in the literature. The bioprospecting of U1-SCRTX-lg1a resulted in the identification of three hundred (300) diverse targets (Table S1), forty-nine (49) of which were intracellular proteins originating from Gram-negative microorganisms (Table S2). Docking results indicate Scores (10,702 to 6066), Areas (1498.70 to 728.40) and ACEs (417.90 to - 152.8) values. Among these, NAD + NH3-dependent synthetase (PDB ID: 1wxi) showed a dock score of 9742, area of 1223.6 and ACE of 38.38 in addition to presenting a Normalized Fit score of 8812 on PharmMapper server. Analysis of the interaction of ligands and receptors suggests that the peptide derived from brown spider venom can interact with residues SER48 and THR160. Furthermore, the C terminus (- 7.0 score) has greater affinity for the receptor than the N terminus (- 7.7 score). The molecular dynamics assay shown that free energy value for the protein complex of - 214,890.21 kJ/mol, whereas with rigid docking, this value was - 29.952.8 sugerindo that after the molecular dynamics simulation, the complex exhibits a more favorable energy value compared to the previous state. The in silico bioprospecting of receptors suggests that U1-SCRTX-lg1a may interfere with NAD + production in Escherichia coli, a Gram-negative bacterium, altering the homeostasis of the microorganism and impairing growth. Supplementary Information: The online version contains supplementary material available at 10.1007/s40203-024-00190-8.

Mygalin, an Acanthoscurria gomesiana spider-derived synthetic, modulates haloperidol-induced cataleptic state in mice.

BACKGROUND: Haloperidol (HAL) is an antipsychotic used in the treatment of schizophrenia. However, adverse effects are observed in the extrapyramidal tracts due to its systemic action. Natural compounds are among the treatment alternatives widely available in Brazilian biodiversity. Mygalin (MY), a polyamine that was synthesized from a natural molecule present in the hemolymph of the Acanthoscurria gomesian spider, may present an interesting approach. AIMS: This study aimed to evaluate the effect of MY in mice subjected to HAL-induced catalepsy. METHODS: Male Swiss mice were used. Catalepsy was induced by intraperitoneal administration of HAL (0.5 mg/kg - 1 mL/Kg) diluted in physiological saline. To assess the MY effects on catalepsy, mice were assigned to 4 groups: (1) physiological saline (NaCl 0.9 %); (2) MY at 0.002 mg/Kg; (3) MY at 0.02 mg/Kg; (4) MY at 0.2 mg/Kg. MY or saline was administered intraperitoneally (IP) 10 min b HAL before saline. Catalepsy was evaluated using the bar test at 15, 30, 60, 90, and 120 min after the IP administration of HAL. RESULTS: The latency time in the bar test 15, 30, 60, and 90 min increased (p < 0.05) after IP administration of HAL compared to the control group. Catalepsy was attenuated 15, 30, 90, and 120 min (p < 0.05) after the IP-administration of MY at 0.2 mg/Kg; while MY at 0.02 mg/Kg attenuated catalepsy 15 min after the HAL treatment. Our findings showed that MY attenuates the HAL-induced cataleptic state in mice.

In Silico and In Vitro Approach for Evaluation of the Anti-Inflammatory and Antioxidant Potential of Mygalin.

There is a great interest in describing new molecules to be used as therapeutic targets in various diseases, particularly those that play a role in inflammatory responses and infection control. Mygalin is a synthetic analogue of spermidine, and previous studies have demonstrated its bactericidal effect against Escherichia coli, as well as its ability to modulate the inflammatory response of macrophages against lipopolysaccharide (LPS). However, the mechanisms through which mygalin regulates this inflammatory response remain poorly characterized. A set of platforms using molecular docking analysis was employed to analyze various properties of mygalin, including toxicity, biodistribution, absorption, and the prediction of its anti-inflammatory properties. In in vitro assays, we evaluated the potential of mygalin to interact with products of the inflammatory response, such as reactive oxygen species (ROS) and antioxidant activity, using the BMDM cell. The in silico analyses indicated that mygalin is not toxic, and can interact with proteins from the kinase group, and enzymes and receptors in eukaryotic cells. Molecular docking analysis showed interactions with key amino acid residues of COX-2, iNOS and 5-LOX enzymes. In vitro, assays demonstrated a significant reduction in the expression of iNOS and COX-2 induced by LPS, along with a decrease in the oxidative stress caused by the treatment with PMA, all without altering cell viability. Mygalin exhibited robust antioxidant activity in DPPH assays, regardless of the dose used, and inhibited heat-induced hemolysis. These studies suggest that mygalin holds promise for further investigation as a new molecule with anti-inflammatory and antioxidant properties.

Molecular hybridization strategy for tuning bioactive peptide function.

The physicochemical and structural properties of antimicrobial peptides (AMPs) determine their mechanism of action and biological function. However, the development of AMPs as therapeutic drugs has been traditionally limited by their toxicity for human cells. Tuning the physicochemical properties of such molecules may abolish toxicity and yield synthetic molecules displaying optimal safety profiles and enhanced antimicrobial activity. Here, natural peptides were modified to improve their activity by the hybridization of sequences from two different active peptide sequences. Hybrid AMPs (hAMPs) were generated by combining the amphipathic faces of the highly toxic peptide VmCT1, derived from scorpion venom, with parts of four other naturally occurring peptides having high antimicrobial activity and low toxicity against human cells. This strategy led to the design of seven synthetic bioactive variants, all of which preserved their structure and presented increased antimicrobial activity (3.1-128 µmol L-1). Five of the peptides (three being hAMPs) presented high antiplasmodial at 0.8 µmol L-1, and virtually no undesired toxic effects against red blood cells. In sum, we demonstrate that peptide hybridization is an effective strategy for redirecting biological activity to generate novel bioactive molecules with desired properties.

In silico bioprospecting of receptors for Doderlin: an antimicrobial peptide isolated from Lactobacillus acidophilus.

The emergence of resistant bacteria strains against traditional antibiotics and treatments increases each year. Doderlin is a cationic and amphiphilic peptide active against gram-positive, negative and yeast stains. The aim of the present work was prospect potentials receptors associated of antimicrobial activity of Doderlin using in silico bioinformatics tools. To search for potential targets of Doderlin, PharmMapper software was used. Molecular docking between Doderlin and the receptor was performed by PatchDock. Additional interaction and ligand site prediction for each receptor was performed by I-TASSER software. Those PDB Id, 1XDJ (score: 11,746), 1JMH (score: 11,046), 1YR3 (score: 10,578), 1NG3 (score: 10,082) showed highest dock score. Doderlin was found to predicted/real sites co-localize with 1XDJ and 1JMH, enzymes accountable for nitrogenic bases synthesis. The resulting receptor bioprospecting is highly correlated and suggests that Doderlin might act by interfering with DNA metabolism/production of bacteria, altering microorganism homeostasis and growth impairment. Supplementary Information: The online version contains supplementary material available at 10.1007/s40203-023-00149-1.

Acanthoscurria gomesiana spider-derived synthetic mygalin in the dorsal raphe nucleus modulates acute and chronic pain.

Mygalin, a diacylspermidine that is naturally found in the hemolymph of the spider Acanthoscurria gomesiana, is of interest for development as a potential analgesic. Previous studies have shown that acylpolyamines modulate glutamatergic receptors with the potential to alter pain pathways. This study aimed to evaluate the effects of mygalin on acute and chronic pain in rodents. For evaluation of acute pain, Wistar rats were subjected to tail-flick and hot-plate nociceptive tests. For the evaluation of chronic neuropathic pain, a partial ligation of the sciatic nerve was performed and, 21 days later, animals were examined in hot-plate, tail-flick, acetone, and von Frey tests. Either Mygalin or vehicle was microinjected in the dorsal raphe nucleus (DRN) before the tests. Another group was pretreated with selective antagonists of glutamate receptors (LY 235959, MK-801, CNQX, and NBQX). Mygalin decreases nociceptive thresholds on both acute and chronic neuropathic pain models in all the tests performed. The lowest dose of mygalin yielded the most effective nociception, showing an increase of 63% of the nociceptive threshold of animals with neuropathic chronic pain. In conclusion, mygalin microinjection in the DRN results in antinociceptive effect in models of neuropathic pain, suggesting that acylpolyamines and their derivatives, such as this diacylspermidine, could be pursued for the treatment of neuropathic pain and development of selective analgesics.

Insights into Antimicrobial Peptides from Limacus flavus Mucus.

Antimicrobial peptides have been a major research subject since the rise of antimicrobial resistance as a major public health problem. These molecules are considered a potential therapeutic source of antibiotics with broad-spectrum activity against microorganisms. Two antimicrobial peptides were isolated from the mucus of the Limacus flavus slug. The mucus was obtained by thermal shock, lyophilized and extracted with acetic acid. The supernatant was prefractionated in Sep-Pak and shortly thereafter fractionated by reverse-phase high-performance liquid chromatography. The manually obtained fractions were used in antimicrobial and cytotoxic assays and finally subjected to mass spectrometry (MS/MS). Characterization was performed by bioinformatics analysis with the tool Peaks®X + and by comparison with the NCBI and UniProt-SwissProt databases. Additionally, the physicochemical parameters of the samples were evaluated with online programs. Two fractions comtained antimicrobial peptides with the ability to inhibit Micrococcus luteus A270; both samples, LFMP-001 and LFMP-002, were hydrophilic molecules consisting of fewer than 20 residues. Comparison of the SDS-PAGE and Peaks®X + data showed that both had Mw < 3 kDa. In summary, this study presents data on the isolation and characterization of antimicrobial peptides from a slug and shows their potential against gram-positive bacteria.

Protein Components of the Arthrodial Membrane Gland in a Neotropical Harvestman (Arachnida, Opiliones).

The content of arthrodial membrane glands in arthropods has seldom been studied. Here, we have analyzed the proteins of the arthrodial membrane gland of the trochanter-coxa articulation of the fourth pair of legs in the harvestman Mischonyx cuspidatus via reverse-phase high-performance liquid chromatography (RP-HPLC), polyacrylamide gel electrophoresis (PAGE), and nanoscale liquid chromatography coupled to mass spectrometry (nLC-MS/MS) analysis. Most of the fractions studied are hydrophobic, being proteins with molecular weights of ∼28, 62, and ∼198 kDa. These proteins seem to be homologous to proteins involved in product secretion, cytoskeleton, protein binding, cellular metabolism, and antimicrobial action among others. Lubricant function is also possible based on the literature. We were able to identify 147 proteins in the inner region, 91 proteins from the outer dorsal region, and 36 proteins from the outer ventral region. Some proteins are present only in one of these regions and some are shared by one or more regions. Our work provides, to the best of our knowledge, the first proteome characterization of the content of an arthrodial membrane gland in arachnids. Dataset Identifier: ftp://massive.ucsd.edu/MSV000087195/.

Acylpolyamine Mygalin as a TLR4 Antagonist Based on Molecular Docking and In Vitro Analyses.

Toll-like receptors (TLRs) are transmembrane proteins that are key regulators of innate and adaptive immune responses, particularly TLR4, and they have been identified as potential drug targets for the treatment of disease. Several low-molecular-weight compounds are being considered as new drug targets for various applications, including as immune modulators. Mygalin, a 417 Da synthetic bis-acylpolyamine, is an analog of spermidine that has microbicidal activity. In this study, we investigated the effect of mygalin on the innate immune response based on a virtual screening (VS) and molecular docking analysis. Bone marrow-derived macrophages and the cell lines J774A.1 and RAW 264.7 stimulated with lipopolysaccharide (LPS) were used to confirm the data obtained in silico. Virtual screening and molecular docking suggested that mygalin binds to TLR4 via the protein myeloid differentiation factor 2 (MD-2) and LPS. Macrophages stimulated by mygalin plus LPS showed suppressed gene expression of tumor necrosis factor (TNF-α), interleukine 6 (IL-6), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as inhibition of signaling protein p65 of the nuclear factor κB (NF-κB), resulting in decreased production of nitric oxide (NO) and TNF-α. These results indicate that mygalin has anti-inflammatory potential, being an attractive option to be explored. In addition, we reinforce the importance of virtual screening analysis to assist in the discovery of new drugs.

Two Tachykinin-Related Peptides with Antimicrobial Activity Isolated from Triatoma infestans Hemolymph.

Antimicrobial peptides and proteins (AMPs) are molecules that can interact with microbial cells and lead to membrane disruption or intracellular molecule interactions and death. Several molecules with antimicrobial effects also present other biological activities. One such protein group representing the duplicity of activities is the tachykinin family. Tachykinins (TKs) form a family of neuropeptides in vertebrates with a consensus C-terminal region (F-X-G-Y-R-NH2). Invertebrate TKs and TK-related peptides (TKRPs) are subfamilies found in invertebrates that present high homology with TKs and have similar biological effects. Several of these molecules have already been described but reports of TKRP in Hemiptera species are limited. By analyzing the Triatoma infestans hemolymph by reversed-phase high-performance liquid chromatography, biological assays, and mass spectrometry, two antimicrobial molecules were isolated and identified as TKRPs, which we named as TRP1-TINF and TRP2-TINF (tachykinin-related peptides I and II from T. infestans). TRP1-TINF is a random secondary structure peptide with 9 amino acid residues. It is susceptible to aminopeptidases degradation and is active mainly against Micrococcus luteus (32 µM). TRP2-TINF is a 10-amino acid peptide with a 310 helix secondary structure and is susceptible to carboxypeptidases degradation. It has major antimicrobial activity against both Pseudomonas aeruginosa and Escherichia coli (45 µM). Neither molecule is toxic to human erythrocytes and both present minor toxicity toward Vero cells at a concentration of 1000 µM. As the first description of TKRPs with antimicrobial activity in T. infestans, this work contributes to the wider comprehension of the insects' physiology and describes pharmacological relevant molecules.

Chemical characterization of the lipids in femoral gland secretions of wild male tegu lizards, Salvator merianae (Squamata, Teiidae) in comparison with captive-bred males.

Although chemical interactions play an essential role in lizard social behavior, the chemical composition of the femoral gland secretions that many lizards use for communication is known for only a few species, mainly European Lacertids. The tegu lizard, Salvator merianae, is the only species of the Teiidae family for which there is available information on lipids in femoral secretions, but only for captive bred males from Argentina. Here, based on mass spectra obtained by GC-MS, we found 69 lipophilic compounds in femoral gland secretions of wild males S. merianae from Brazil, including cholesterol and high amounts of saturated fatty acids (mainly hexadecanoic and octadecanoic). We found contrasting differences between wild and captive-bred males, which lack cholesterol but present high amount of 9,12-octadecadienoic acid. These within-species differences between wild and captive lizards strongly suggest the important influence of different diets on the chemical composition of the femoral gland secretion and suggest caution when interpreting results from captive animals, even in the same species.

Hemoglobin Reassembly of Antimicrobial Fragments from the Midgut of Triatoma infestans.

Hemoglobin is one of the most important molecules of the human body. Beyond its physiological activity, hemoglobins are able to inhibit the growth of several microorganisms. Since 1999, studies have reported that antimicrobial peptides can be produced by blood-feeding insects through hemoglobin digestion, and it has been reported that Triatoma infestans can generate an antimicrobial fragment from human fibrinopeptide. Thus T. infestans intestinal content was analyzed through Reverse Phase High-Performance Liquid Chromatography (RP-HPLC), the eluted fractions were tested against Micrococcus luteus, Escherichia coli and Staphylococcus aureus, and the active fractions submitted to mass spectrometry. The data obtained were compared to hemoglobin databases to verify the presence of hemoglobin-derived fragments. Ten fractions eluted from chromatography presented antimicrobial activity, and when analyzed through mass spectrometry revealed the presence of 8 murine hemoglobin α-chain fragments and 24 fragments from murine hemoglobin ß fragments. Through the compilation of the fragments is possible to obtain over 67% coverage of both sequences. Part of the amino acid sequences corresponds to the sequences already identified on other intestinal contents of arthropods, and are highly conserved between the blood of other wild animals that are the most common intermediate hosts of Chagas' disease in Brazil and some of the main natural blood source for triatomines.

Patagonin-CRISP: Antimicrobial Activity and Source of Antimicrobial Molecules in Duvernoy's Gland Secretion (Philodryas patagoniensis Snake).

Snake venom contains a variety of toxins with a range of biological activity, among these toxins cysteine-rich secreted proteins (CRISPs) can be found. The proteins of this family have masses of 20-30 kDa and display homologous amino acid sequences containing 16 cysteine residues, forming eight disulfide bonds. Some of these proteins have been explored, characterized, and described in terms of their activity; however, little is known about their range of activities. A search for new antimicrobial molecules is ongoing, as the number of microbial strains resistant to available antibiotics is increasing. We identified antimicrobial activity in the secretion of Duvernoy's gland of the rear-fanged Philodryas patagoniensis. Fractions of this venom were subjected to reverse-phase high performance liquid chromatography and analyzed to determine their antimicrobial activity with a liquid broth inhibition assay. One of the fractions presented activity against a Gram-negative bacterium and a filamentous fungus. This fraction was analyzed with LC-MS/MS, and a protein of 24,848.8 Da was identified. Database searches allowed us to identify it as a CRISP due to the presence of some unique fragments in the molecule. We called it patagonin-CRISP, as the same protein in the venom of P. patagoniensis had previously been characterized as having a different biological activity. Patagonin-CRISP presented activity at very low concentrations and showed no cytotoxic activity. This is the first time that antimicrobial activity has been identified for P. patagoniensis venom or for a CRISP family protein.

Serrulin: A Glycine-Rich Bioactive Peptide from the Hemolymph of the Yellow Tityus serrulatus Scorpion.

Antimicrobial peptides (AMPs) are small molecules, which have a potential use as antibiotic or pharmacological tools. In chelicerate organisms, such as scorpions, these molecules constitute an alternative defense system against microorganisms. The aim of this work was to identify AMPs in the hemolymph of the Tityus serrulatus scorpion. Fractions of plasma and hemocytes were subjected to high-performance liquid chromatography (HPLC) and then analyzed to determine their activity in inhibiting microbial growth. One of the fractions from the hemocytes presents antimicrobial activity against microorganisms, such as Gram-negative and Gram-positive bacteria, fungi, and yeast. These fractions were analyzed by mass spectrometry, and a fragment of 3564 Da. was identified. The peptide was called serrulin, because it is derived from the species T. serrulatus. A comparison of the amino acid sequence of serrulin with databases shows that it has a similarity to the glycine-rich peptides described in Cupienius salai and Acanthoscurria gomesiana (spiders). Furthermore, serrulin has no hemolytic activity against human erythrocytes. While the presence of AMPs in T. serrulatus venom has been described in other works, this is the first work to characterize the presence of these molecules in the hemolymph (hemocytes) of this species and show its potential use as an alternative to conventional antibiotics against different species of microorganisms.

The effect of lysine substitutions in the biological activities of the scorpion venom peptide VmCT1.

Antimicrobial peptides (AMPs) are biologically active molecules with a broad-spectrum activity against a myriad of microorganisms. Aside from their antimicrobial functions, AMPs present physicochemical and structural properties that allow them to exert activity against other kind of cells, such as cancer cells. VmCT1 is a potent cationic amphipathic AMP from the venom of the scorpion Vaejovis mexicanus. In this study, we designed lysine-substituted VmCT1 analogs for verifying the influence of changes in the net positive charge on biological activities. The increase in the net positive charge caused by lysine substitutions in the hydrophilic portion, led to higher antimicrobial activity values (0.1-6.3 µmol L-1) than VmCT1 (0.8-50 µmol L-1) and higher activity against mammary cancer cells MCF-7 (6.3-12.5 µmol L-1) than VmCT1 (12.5 µmol L-1). Contrarily, when lysine-substitutions were made at the hydrophobic portion of the helical projection, the activity values decreased. However, the lysine-substitution at the center of the hydrophobic face led to the generation of an analog with antiplasmodial activity at the same concentration presented by VmCT1 (0.8 µmol L-1). In this study, we demonstrated that it is possible to modulate biological activities and cytotoxicity of VmCT1 peptides by increasing their net positive charge using lysine residues, thus creating alternatives for standard-of-care therapeutics against different types of microorganisms and MCF-7 human breast cancer cells.

Repurposing the scorpion venom peptide VmCT1 into an active peptide against Gram-negative ESKAPE pathogens.

VmCT1 is a cationic antimicrobial peptide (AMP) from the venom of the scorpion Vaejovis mexicanus. VmCT1 and analogs were designed with single substitutions for verifying the influence of changes in physicochemical features described as important for AMPs antimicrobial and hemolytic activities, as well as their effect on VmCT1 analogs resistance against proteases action. The increase of the net positive charge by the introduction of an arginine residue in positions of the hydrophilic face of the helical structure affected directly the antimicrobial activity. Arg-substituted analogs presented activity against Gram-negative bacteria from the ESKAPE list of pathogens that were not observed for VmCT1. Additionally, peptides with higher net positive charge presented increased antimicrobial activity with values ranging from 0.39 to 12.5 µmol L-1 against Gram-positive and Gram-negative bacteria and fungi. The phenylalanine substitution by glycine (position 1), and the valine substitution by a proline residue (position 8) led to analogs with lower hemolytic activity (at concentrations 50 and 100 µmol L-1, respectively). These results revealed that it is possible to modulate the biological activities of VmCT1 derivatives by designing single substituted-analogs as prospective therapeutics against bacteria and fungi.

Longipin: An Amyloid Antimicrobial Peptide from the Harvestman Acutisoma longipes (Arachnida: Opiliones) with Preferential Affinity for Anionic Vesicles.

In contrast to vertebrate immune systems, invertebrates lack an adaptive response and rely solely on innate immunity in which antimicrobial peptides (AMPs) play an essential role. Most of them are membrane active molecules that are typically unstructured in solution and adopt secondary/tertiary structures upon binding to phospholipid bilayers. This work presents the first characterization of a constitutive AMP from the hemolymph of an Opiliones order animal: the harvestman Acutisoma longipes. This peptide was named longipin. It presents 18 aminoacid residues (SGYLPGKEYVYKYKGKVF) and a positive net charge at neutral pH. No similarity with other AMPs was observed. However, high sequence similarity with heme-lipoproteins from ticks suggested that longipin might be a protein fragment. The synthetic peptide showed enhanced antifungal activity against Candida guilliermondii and C. tropicalis yeasts (MIC: 3.8-7.5 µM) and did not interfered with VERO cells line viability at all concentrations tested (200-0.1 µM). This selectivity against microbial cells is related to the highest affinity of longipin for anionic charged vesicles (POPG:POPC) compared to zwitterionic ones (POPC), once microbial plasma membrane are generally more negatively charged compared to mammalian cells membrane. Dye leakage from carboxyfluorescein-loaded POPG:POPC vesicles suggested that longipin is a membrane active antimicrobial peptide and FT-IR spectroscopy showed that the peptide chain is mainly unstructured in solution or in the presence of POPC vesicles. However, upon binding to POPG:POPC vesicles, the FT-IR spectrum showed bands related to ß-sheet and amyloid-like fibril conformations in agreement with thioflavin-T binding assays, indicating that longipin is an amyloid antimicrobial peptide.

Evidence of an Antimicrobial Peptide Signature Encrypted in HECT E3 Ubiquitin Ligases.

The ubiquitin-proteasome pathway (UPP) is a hallmark of the eukaryotic cell. In jawed vertebrates, it has been co-opted by the adaptive immune system, where proteasomal degradation produces endogenous peptides for major histocompatibility complex class I antigen presentation. However, proteolytic products are also necessary for the phylogenetically widespread innate immune system, as they often play a role as host defense peptides (HDPs), pivotal effectors against pathogens. Here, we report the identification of the arachnid HDP oligoventin, which shares homology to a core member of the UPP, E3 ubiquitin ligases. Oligoventin has broad antimicrobial activity and shows strong synergy with lysozymes. Using computational and phylogenetic approaches, we show high conservation of the oligoventin signature in HECT E3s. In silico simulation of HECT E3s self-proteolysis provides evidence that HDPs can be generated by fine-tuned 26S proteasomal degradation, and therefore are consistent with the hypothesis that oligoventin is a cryptic peptide released by the proteolytic processing of an Nedd4 E3 precursor protein. Finally, we compare the production of HDPs and endogenous antigens from orthologous HECT E3s by proteasomal degradation as a means of analyzing the UPP coupling to metazoan immunity. Our results highlight the functional plasticity of the UPP in innate and adaptive immune systems as a possibly recurrent mechanism to generate functionally diverse peptides.

Antimicrobial activity of the toxin VdTX-I from the spider Vitalius dubius (Araneae, Theraphosidae).

BACKGROUND: Currently there is an urgent need to develop new classes of antimicrobial agents with different mechanisms of action from conventionally antibiotics used for the control of pathogenic microorganisms. The acylpolyamine called VdTX-I was isolated from the venom of the tarantula Vitalius dubius, and first described with activity as an antagonist of nicotinic cholinergic receptors. The main objective of this study was to investigate the antimicrobial activity found in the venom of the spider, with emphasis on the toxin VdTX-I. METHODS: Antimicrobial assays were performed in 96 well plates culture against 14 micro-organisms (fungi, yeasts and bacteria), which were tested concentrations from 0.19 to 100 µM of VdTX-I. After qualitative analysis, dose-response curve assays were performed in bacterial kill curve using MTT reagent and hemolytic assay. RESULTS: The antimicrobial activity of the VdTX-I toxin was observed in 12 tested species of Candida, Trichosporiun, Staphylococcus and Micrococcus. The toxicity had a dose-response at 3.12 µM - 100 µM in Candida albicans, Candida guillermondii, Micrococcus luteus and Escherichia coli. VdTX-I took about 5 min to inhibit bacterial growth, which was faster than streptomycin. The toxin showed no hemolytic activity between 0.19 and 100 µM. At 2.5 µg/mL of toxin it was observed no growth inhibition against a mammalian cell lineage. CONCLUSIONS: The VdTX-I toxin has a significant antimicrobial activity, with broad spectrum, and is experimentally inert to mammalian blood cells. GENERAL SIGNIFICANCE: This paper explores the antimicrobial potential of the spider toxin VdTX-I, which can provide a new model to design new antimicrobial drugs.

Mygalin: a new anticonvulsant polyamine in acute seizure model and neuroethological schedule.

Polyamines are compounds that interact with ionotropic receptors, mainly modulating the NMDA receptor, which is strictly related to many neurologic diseases such as epilepsy. Consequently, polyamines rise as potential neuropharmacological tools in the prospection of new therapeutic drugs. In this paper, we report on the biological activity of synthetic polyamine Mygalin, which was tested as an anticonvulsant in model of chemically induced seizures. Male Wistar rats were injected with vehicle, diazepam, MK-801 or Mygalin at different doses followed by Pentylenetetrazole or N-Methyl-D-Aspartate administration. Mygalin presented protection against seizures induced by both NMDA injections and PTZ administration by 83.3% and 16.6%, respectively. Moreover, it prolonged the onset of tonic-clonic seizures induced by PTZ. Furthermore, it was tested in neuroethological schedule evaluating possible side-effects and it presented mild changes in Open Field, Rotarod and Morris Water Maze tests when compared to available anticonvulsant drugs. The mechanism underlying the anticonvulsant effect of Mygalin is noteworthy of further investigation, nevertheless, based on these findings, we hypothesize that it may be wholly or in part due to a possible NMDA receptor antagonism. Altogether, the results demonstrate that Mygalin has an anticonvulsant activity that may be an important tool in the study of prospection of therapeutics in epilepsy neuropharmacology.