Characterization of Tachyplesin peptides and their cyclized analogues to improve antimicrobial and anticancer properties

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Tachyplesin I, II and III are host defense peptides from horseshoe crab species with antimicrobial and anticancer activities. They have an amphipathic β-hairpin structure, are highly positively-charged and differ by only one or two amino acid residues. In this study, we compared the structure and activity of the three tachyplesin peptides alongside their backbone cyclized analogues. We assessed the peptide structures using nuclear magnetic resonance (NMR) spectroscopy, then compared the activity against bacteria (both in the planktonic and biofilm forms) and a panel of cancerous cells. The importance of peptide-lipid interactions was examined using surface plasmon resonance and fluorescence spectroscopy methodologies. Our studies showed that tachyplesin peptides and their cyclic analogues were most potent against Gram-negative bacteria and melanoma cell lines, and showed a preference for binding to negatively-charged lipid membranes. Backbone cyclization did not improve potency, but improved peptide stability in human serum and reduced toxicity toward human red blood cells. Peptide-lipid binding affinity, orientation within the membrane, and ability to disrupt lipid bilayers differed between the cyclized peptide and the parent counterpart. We show that tachyplesin peptides and cyclized analogues have similarly potent antimicrobial and anticancer properties, but that backbone cyclization improves their stability and therapeutic potential.This project was funded by a National Health Medical Research Council (NHMRC) project grant (APP1084965). F.V. was supported by the UQ Research Scholarship, S.T.H. is an Australian Research Council (ARC) Future Fellow (FT150100398), D.J.C. is an ARC Australian Laureate Fellow (FL150100146). Marie Skłodowska-Curie Research and Innovation Staff Exchange grant (RISE; call: H2020-MSCA-RISE-2014, grant agreement 644167) funded secondments of S.A.D. and of A.S.V. to the University of Queensland. The Translational Research Institute is supported by a grant from the Australian Government.info:eu-repo/semantics/publishedVersio

Mechanisms of bacterial membrane permeabilization by crotalicidin Ctn and its fragment Ctn 15–34, antimicrobial peptides from rattlesnake venom

© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.Crotalicidin (Ctn), a cathelicidin-related peptide from the venom of a South American rattlesnake, possesses potent antimicrobial, antitumor, and antifungal properties. Previously, we have shown that its C-terminal fragment, Ctn(15-34), retains the antimicrobial and antitumor activities but is less toxic to healthy cells and has improved serum stability. Here, we investigated the mechanisms of action of Ctn and Ctn(15-34) against Gram-negative bacteria. Both peptides were bactericidal, killing ∼90% of Escherichia coli and Pseudomonas aeruginosa cells within 90-120 and 5-30 min, respectively. Studies of ζ potential at the bacterial cell membrane suggested that both peptides accumulate at and neutralize negative charges on the bacterial surface. Flow cytometry experiments confirmed that both peptides permeabilize the bacterial cell membrane but suggested slightly different mechanisms of action. Ctn(15-34) permeabilized the membrane immediately upon addition to the cells, whereas Ctn had a lag phase before inducing membrane damage and exhibited more complex cell-killing activity, probably because of two different modes of membrane permeabilization. Using surface plasmon resonance and leakage assays with model vesicles, we confirmed that Ctn(15-34) binds to and disrupts lipid membranes and also observed that Ctn(15-34) has a preference for vesicles that mimic bacterial or tumor cell membranes. Atomic force microscopy visualized the effect of these peptides on bacterial cells, and confocal microscopy confirmed their localization on the bacterial surface. Our studies shed light onto the antimicrobial mechanisms of Ctn and Ctn(15-34), suggesting Ctn(15-34) as a promising lead for development as an antibacterial/antitumor agent.This work was supported by Spanish Ministry of Economy and Competitiveness (MINECO) Grants SAF2011-24899 and AGL2014-52395-C2, by Fundação para a Ciência e a Tecnologia (FCT, Portugal) Grants PTDC/QEQ-MED/4412/2014, and by EU Marie Skłodowska-Curie Research and Innovation Staff Exchange (RISE) program Grant 644167, 2015–2019.info:eu-repo/semantics/publishedVersio

Identification of survival-promoting OSIP108 peptide variants and their internalization in human cells

The plant-derived decapeptide OSIP108 increases tolerance of yeast and human cells to apoptosis-inducing agents, such as copper and cisplatin. We performed a whole amino acid scan of OSIP108 and conducted structure-activity relationship studies on the induction of cisplatin tolerance (CT) in yeast. The use of cisplatin as apoptosis-inducing trigger in this study should be considered as a tool to better understand the survival-promoting nature of OSIP108 and not for purposes related to anti-cancer treatment. We found that charged residues (Arg, His, Lys, Glu or Asp) or a Pro on positions 4–7 improved OSIP108 activity by 10% or more. The variant OSIP108[G7P] induced the most pronounced tolerance to toxic concentrations of copper and cisplatin in yeast and/or HepG2 cells. Both OSIP108 and OSIP108[G7P] were shown to internalize equally into HeLa cells, but at a higher rate than the inactive OSIP108[E10A], suggesting that the peptides can internalize into cells and that OSIP108 activity is dependent on subsequent intracellular interactions. In conclusion, our studies demonstrated that tolerance/survival-promoting properties of OSIP108 can be significantly improved by single amino acid substitutions, and that these properties are dependent on (an) intracellular target(s), yet to be determined

Cyclotides as templates in drug design

© 2009 Elsevier Ltd. All rights reservedCyclotides are remarkably stable proteins from plants that have a range of pharmaceutical and agricultural applications based on both their various bioactivities and their potential for use as stable protein-engineering templates. This article discusses literature on pharmaceutically relevant activities of cyclotides, including anti-HIV, antimicrobial and cytotoxic activities, and evaluates their potential therapeutic applications. Their applications as templates for the design of antiangiogenic agents for the treatment of cancer and as anti-infective agents are also described. Toxic effects of cyclotides, whose native function is as insecticidal agents, can be removed by simple mutagenesis, thus rationalizing the apparent conundrum of proposing insecticidal agents as leads for human therapeutics.Studies in our laboratory on cyclotides are supported by grants from the Australian Research Council (DP0880105) and the National Health and Medical Research Council (NHMRC). D.J.C. is an NHMRC Professorial Fellow. S.T.H. is a Marie Curie Postdoctoral Fellowawarded by EuropeanCommission (PIOF-GA-2008-220318)

Antimicrobial peptides provide wider coverage for targeting drug-resistant bacterial pathogens

We need new treatment options to control bacterial infections. Bacteria use several strategies to resist drug treatment, including modification of the drug target, and adaptation to a different lifestyle, such as intracellular niches within host cells. Drugs that act on diverse targets are less likely to induce resistance in bacteria, than current antibiotics acting on a single molecular target. Antimicrobial peptides have been explored as a new class of antibiotics because they selectively kill bacteria via a mechanism that involves recognition of the negatively charged microbial surface. Furthermore, antimicrobial peptides with cell-penetrating properties can cross host cell membranes and target bacteria in the cytosol or sequestered in vesicles. Therefore, bacteria in intracellular niches are less capable of evading treatment and the likelihood of establishing drug resistance is further reduced. This review highlights the potential of antimicrobial peptides as alternative therapeutics to target bacterial pathogens in both extracellular and intracellular environments, and to avoid acquired drug-resistance.</p

Cyclic analogues of horseshoe crab peptide Tachyplesin I with anticancer and cell penetrating properties

Tachyplesin-I (TI) is a host defense peptide from the horseshoe crab Tachypleus tridentatus that has outstanding potential as an anticancer therapeutic lead. Backbone cyclized TI (cTI) has similar anticancer properties to TI but has higher stability and lower hemolytic activity. We designed and synthesized cTI analogues to further improve anticancer potential and investigated structure-activity relationships based on peptide-membrane interactions, cellular uptake, and anticancer activity. The membrane-binding affinity and cytotoxic activity of cTI were found to be highly dependent on peptide hydrophobicity and charge. We describe two analogues with increased selectivity toward melanoma cells and one analogue with the ability to enter cells with high efficacy and low toxicity. Overall, the structure-activity relationship study shows that cTI can be developed as a membrane-active antimelanoma lead, or be employed as a cell penetrating peptide scaffold that can target and enter cells without damaging their integrity

Structural and functional analysis of human liver-expressed antimicrobial peptide 2

© 2010 WILEY-VCHHuman liver-expressed antimicrobial peptide 2 (LEAP-2) is a cationic antimicrobial peptide (CAMP) believed to have a protective role against bacterial infection. Little is known about the structure–activity relationships of LEAP-2 or its mechanism of ction. In this study we describe the structure of LEAP-2, analyze its interaction with model membranes, and relate them to the antimicrobial activity of the peptide. The structure of LEAP-2, determined by NMR spectroscopy, reveals a compact central core with disorder at the N and C termini. The core comprises a β-hairpin and a 3ıо- helix that are braced by disulfide bonds between Cys17–28 and Cys23–33 and further stabilized by a network of hydrogen bonds. Membrane-affinity studies show that LEAP-2 membrane binding is governed by electrostatic attractions, which are sensitive to ionic strength. Truncation studies show that the C-terminal region of LEAP-2 is irrelevant for membrane binding, whereas the N-terminal (hydrophobic domain) and core regions (cationic domain) are essential. Bacterial-growth-inhibition assays reveal that the antimicrobial activity of LEAP-2 correlates with membrane affinity. Interestingly, the native and reduced forms of LEAP-2 have similar membrane affinity and antimicrobial activities ; this suggests that disulfide bonds are not essential for the bactericidal activity. This study reveals that LEAP-2 has a novel fold for a CAMP and suggests that although LEAP-2 exhibits antimicrobial activity under low-salt conditions, there is likely to be another physiological role for the peptide.Work in our laboratory on LEAP-2 is supported by a grant (456073) from the National Health and Medical Research Council (NHMRC) to R.J.C. and D.J.C.. S.T.H. is a Marie Curie International Outgoing Fellow within the 7th European Community Framework Program. D.J.C. is a NHMRC Principal Research Fellow. R.J.C. is a NHMRC Biomedical Career Development Award Fello

The toxicity of prion protein fragment PrP(106-126) is not mediated by membrane permeabilization as shown by a M112W substitution

© 2009 American Chemical Society - The final version of record is available at http://pubs.acs.org/journal/bichawPrion diseases result from a post-translational modification of the physiological prion protein (PrPC) into a scrapie isoform (PrPSc). The PrP(106-126) fragment is conserved among various abnormal variants and shows PrPSc pathogenic properties. It has been proposed that the PrP(106-126) fragment may exhibit its toxic effects through membrane pore formation. Our previous studies showed that PrP(106-126) does not interact with membranes under physiological conditions. In the present study, PrP(106-126) affinity for membranes was increased by modifying PrP(106-126) with a M112W substitution, and pore formation was further evaluated. However, while the peptide exhibited an increased local concentration in the membrane, this did not lead to the induction of membrane permeabilization, as verified by fluorescence methodologies and surface plasmon resonance. These results further support the idea that PrP(106-126) toxicity is not a consequence of peptide-membrane interaction and pore formation.Fundação para a Ciência e Tecnologia (Portugal) is acknowledged for Grant SFRH/BD/14337/2003 to S.T.H. IUBMB is acknowledged for financial support to S.T.H. for a short-term visit to the MIA laboratory at Monash University, Victoria, Australia. The support of the Australian Research Council and the Potter Foundation is gratefully acknowledged

Energy-independent translocation of cell-penetrating peptides occurs without formation of pores. A biophysical study with pep-1.

Pep-1 is a cell-penetrating peptide (CPP) with the ability to translocate across biological membranes and introduce active proteins inside cells. The uptake mechanism used by this CPP is, as yet, unknown in detail. Previous results show that such a mechanism is endocytosis-independent and suggests that physical-chemical interactions between the peptide and lipid bilayers govern the translocation mechanism. Formation of a transmembrane pore has been proposed but this issue has always remained controversial. In this work the secondary structure of pep-1 in the absence/presence of lipidic bilayers was determined by CD and ATR-FTIR spectroscopies and the occurrence of pore formation was evaluated through electrophysiological measurements with planar lipid membranes and by confocal microscopy using giant unilamellar vesicles. Despite pep-1 hydrophobic domain tendency for amphipathic alpha-helix conformation in the presence of lipidic bilayers, there was no evidence for membrane pores in the presence of pep-1. Furthermore, alterations in membrane permeability only occurred for high peptide/lipid ratios, which induced the complete membrane disintegration. Such observations indicate that electrostatic interactions are of first importance in the pep-1-membrane interactions and show that pores are not formed. A peptide-lipid structure is probably formed during peptide partition, which favours peptide translocation.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Safer in vitro drug screening models for melioidosis therapy development

Melioidosis is a neglected tropical disease caused by the Gram-negative soil bacterium\ua0Burkholderia pseudomallei.\ua0Current antibiotic regimens used to treat melioidosis are prolonged and expensive, and often ineffective because of intrinsic and acquired antimicrobial resistance. Efforts to develop new treatments for melioidosis are limited by the risks associated with handling pathogenic\ua0B. pseudomallei, which restricts research to facilities with biosafety level three containment. Closely related nonpathogenic\ua0Burkholderia\ua0can be investigated under less stringent biosafety level two containment, and we hypothesized that they could be used as model organisms for developing therapies that would also be effective against\ua0B. pseudomallei. We used microbroth dilution assays to compare drug susceptibility profiles of three\ua0B. pseudomallei\ua0strains and five nonpathogenic\ua0Burkholderia\ua0strains.\ua0Burkholderia humptydooensis,\ua0Burkholderia thailandensis, and\ua0Burkholderia territorii\ua0had similar susceptibility profiles to pathogenic\ua0B. pseudomallei\ua0that support their potential as safer in vitro models for developing new melioidosis therapies