Showing papers by "J. Michael Conlon published in 2011"
TL;DR: The low potency of many frog skin antimicrobial peptides is consistent with the hypothesis that cutaneous symbiotic bacteria may provide the major system of defense against pathogenic microorganisms in the environment with antimicrobial Peptide assuming a supplementary role in some species.
Abstract: Cationic peptides that adopt an amphipathic α-helical conformation in a membrane-mimetic environment are synthesized in the skins of many frog species. These peptides often display cytolytic activities against bacteria and fungi consistent with the idea that they play a role in the host’s system of defense against pathogenic microorganisms, but their importance in the survival strategy of the animal is not clearly understood. Despite the common misconception that antimicrobial peptides are synthesized in the skins of all anurans, the species distribution is sporadic, suggesting that their production may confer some evolutionary advantage to the organism but is not necessary for survival. The low potency of many frog skin antimicrobial peptides is consistent with the hypothesis that cutaneous symbiotic bacteria may provide the major system of defense against pathogenic microorganisms in the environment with antimicrobial peptides assuming a supplementary role in some species.
156 citations
TL;DR: The low potency of many frog skin antimicrobial peptides is consistent with the hypothesis that cutaneous symbiotic bacteria may provide the major system of defense against pathogenic microorganisms in the environment with antimicrobial Peptide assuming a supplementary role in some species.
Abstract: Cationic peptides with the propensity to adopt an amphipathic α-helical conformation in a membrane-mimetic environment are synthesized in the skins of many species of anurans (frogs and toads). These peptides frequently display cytolytic activities against a range of pathogenic bacteria and fungi consistent with the idea that they play a role in the host's system of innate immunity. However, the importance of the peptides in the survival strategy of the animal is not clearly understood. It is a common misconception that antimicrobial peptides are synthesized in the skins of all anurans. In fact, the species distribution is sporadic suggesting that their production may confer some evolutionary advantage to the organism but is not necessary for survival. Although growth inhibitory activity against the chytrid fungus Batrachochytrium dendrobatidis, responsible for anuran population declines worldwide, has been demonstrated in vitro, the ability of frog skin antimicrobial peptides to protect the animal in the wild appears to be limited and there is no clear correlation between their production by a species and its resistance to fatal chytridiomycosis. The low potency of many frog skin antimicrobial peptides is consistent with the hypothesis that cutaneous symbiotic bacteria may provide the major system of defense against pathogenic microorganisms in the environment with antimicrobial peptides assuming a supplementary role in some species.
142 citations
TL;DR: Using a combination of reversed-phase HPLC and electrospray mass spectrometry, peptidomic analysis of norepinephrine-stimulated skin secretions of the American bullfrog Lithobates catesbeianus Shaw, 1802 led to the identification and characterization of five newly described peptides.
35 citations
TL;DR: Comparison of the primary structures of these peptides suggest that western population of X. muelleri is more closely related to X. borealis than toX.muelleri consistent with its proposed designation as a separate species.
32 citations
TL;DR: Dicarba-brevinin-1BYa showed a two-fold increase in potency against reference strains of Escherichia coli, Staphylococcus aureus, and Candidaalbicans compared with the native peptide and displayed potent bactericidal activity against clinical isolates of methicillin-resistant S. aureUS (MRSA) and multidrug-resistant Acinetobacter baumannii.
Abstract: Brevinin-1BYa (FLPILASLAAKFGPKLFCLVTKKC), first isolated from skin secretions of the frog Rana boylii, displays broad-spectrum antimicrobial activity and potent haemolytic activity. This study investigates the effects on conformation and biological activity of replacement of the intramolecular disulphide bridge in the peptide by a non-reducible dicarba bond. Dicarba-brevinin-1BYa was prepared by microwave irradiation of [Agl18,Agl24]-brevinin-1BYa (Agl = allylglycine) in the presence of a second generation Grubbs’ catalyst. Circular dichroism spectroscopy in 50% trifluoroethanol-water indicated that the degree of α-helicity of the dicarba derivative (22%) was less than that of brevinin-1BYa (27%) but comparable to that of the acyclic derivative [Ser18,Ser24]-brevinin-1BYa (23%). Dicarba-brevinin-1BYa showed a two-fold increase in potency against reference strains of Escherichia coli, Staphylococcus aureus, and Candida
albicans compared with the native peptide and displayed potent bactericidal activity against clinical isolates of methicillin-resistant S. aureus (MRSA) and multidrug-resistant Acinetobacter baumannii (MIC in the range 1–8 μM). Compared with brevinin-1BYa and [Ser18,Ser24]-brevinin-1BYa, the dicarba derivative was associated with increased cytotoxicity against human erythrocytes (2.5-fold), MDA-MB-231 breast carcinoma cells (1.3-fold) and HepG2 hepatoma-derived cells (1.5-fold).
32 citations
TL;DR: Although no clear correlation exists between production of dermal antimicrobial peptides by a species and its resistance to fatal chytridiomycosis, the diversity of these peptides in R. pretiosa may be pivotal in defending the species against environmental pathogens such as B. dendrobatidis.
Abstract: Population declines due to chytridiomycosis among frogs belonging to the Amerana (Rana boylii) species group from western North America have been particularly severe. Norepinephrine-stimulated skin secretions from the Oregon spotted frog Rana pretiosa Baird and Girard, 1853 were collected from individuals that had been previously infected with the causative agent Batrachochytrium dendrobatidis but had proved resistant to developing chytridiomycosis. These secretions contained a more diverse array of antimicrobial peptides than found in other species from the Amerana group and 14 peptides were isolated in pure form. Determination of their primary structures identified the peptides as esculentin-2PRa and -2PRb; ranatuerin-2PRa, -2PRb, -2PRc, -2PRd, and -2PRe; brevinin-1PRa, -1PRb, -1PRc, and -1PRd; and temporin-PRa, -PRb, and -PRc. The strongly cationic ranatuerin-2PRd and the esculentin-2 peptides, which have not been identified in the secretions of other Amerana species except for the closely related R. luteiventris, showed the highest growth inhibitory potency against microorganisms. The strongly hydrophobic brevinin-1PRd was the most cytotoxic to erythrocytes. Although no clear correlation exists between production of dermal antimicrobial peptides by a species and its resistance to fatal chytridiomycosis, the diversity of these peptides in R. pretiosa may be pivotal in defending the species against environmental pathogens such as B. dendrobatidis.
30 citations
TL;DR: The most abundant antimicrobial peptide in the secretions, CPF-C1 (GFGSLLGKALRLG ANVL) inhibited the growth of the Gram-negative bacteria Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa suggesting potential for development into an anti-infective agent for use against these emerging antibiotic-resistant pathogens.
Abstract: Five peptides with antimicrobial activity were isolated from norepinephrine-stimulated skin secretions of the tetraploid frog Xenopus clivii Peracca, 1898 (Pipidae). Characterization of the peptides demonstrated that they are structurally similar to magainins (2 peptides), caerulein-precursor fragments, CPF (2 peptides), and xenopsin-precursor fragments, XPF (1 peptide) that have been previously isolated from other species of the genus Xenopus. The magainins and the XPF peptide were active only against the Gram-negative microorganism Escherichia coli whereas the CPF peptides were also active against the Gram-positive Staphylococcus aureus. The most abundant antimicrobial peptide in the secretions, CPF-C1 (GFGSLLGKALRLG ANVL.NH2) inhibited the growth of the Gram-negative bacteria Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa (MIC ≤ 25 μM) suggesting potential for development into an anti-infective agent for use against these emerging antibiotic-resistant pathogens.
27 citations
TL;DR: While their precise biological role is unclear, the caerulein- and xenopsin-related peptides may constitute a component of the animal's chemical defenses against predators.
27 citations
TL;DR: Cladistic analysis based upon the primary structures of brevinin-1 peptides indicates a close phylogenetic relationship between L. chiricahuensis, L. onca, and L. yavapaiensis.
27 citations
TL;DR: Treatment and prevention of acne and periodontal disease are identified as areas in which frog skin antimicrobial peptides might find future applications.
Abstract: Frog skin constitutes a rich source of peptides with broad spectrum antimicrobial activity against strains of antibiotic-resistant bacteria and fungi and several hundred such peptides from diverse species have been described However, their therapeutic potential remains to be realized and no anti-infective peptide based upon their structures has yet been adopted in clinical practice This review assesses potential clinical applications of nine antimicrobial peptides isolated from frog skin (alyteserin-1c, ascaphin-8, brevinin-1BYa, brevinin-2PRa, brevinin-2-related peptide, brevinin-2- related peptide-ERa, kassinatuerin-1, pseudin-2, and temporin-DRa) The multidrug-resistant microorganisms targeted include the Gram-negative bacteria Acinetobacter baumannii, Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa, the Gram-positive bacterium Staphylococcus aureus, and the opportunistic yeast pathogens Candida spp Although the naturally occurring peptides show varying degrees of cytotoxicity towards mammalian cells such as erythrocytes, analogs have been developed that retain high antimicrobial potency but are nonhemolytic Treatment and prevention of acne and periodontal disease are identified as areas in which frog skin antimicrobial peptides might find future applications
26 citations
TL;DR: In this paper, a putative genome duplication event within the Silurana lineage has given rise to the tetraploid frog S. paratropicalis and a second polyploidization within the Xenopus lineage has produced the octoploid frog X. andrei.
TL;DR: The results suggest that the endogenous peptides PACAP and VIP might be implicated in the central control of cardiac baroreflex functions in trout.
TL;DR: It is concluded that multiple pathways involving at least the alpha adrenergic and leukotriene synthesis pathway are involved in mediating the vasoconstrictive actions of BK in vascular smooth muscle of the little skate.
TL;DR: The present study is the first report to describe the molecular cloning of the cDNA encoding a japonicin-2 family peptide, and nucleotide and deduced amino acid sequence analyses revealed that the hypothetical precursor protein is organized similarly to those of typical amphibian AMP precursors, with a highly conserved signal peptide and a relatively well conserved intervening sequence.
Abstract: Using a combination of reverse-transcription polymerase chain reaction and the 5'- and/or 3'-rapid amplification of cDNA ends, we cloned, from a Japanese brown frog (Rana japonica) skin total RNA preparation, cDNAs encoding biosynthetic precursors for the antimicrobial peptides (AMPs) japonicin-1Ja (FFPIGVFCKIFKTC), japonicin-2Ja (FGLPMLSILPKALCILLKRKC), and temporin-1Ja (ILPLVGNLLNDLL.NH2). These peptides were previously isolated from an extract of R. japonica skin. The present study is the first report to describe the molecular cloning of the cDNA encoding a japonicin-2 family peptide. The nucleotide and deduced amino acid sequence analyses revealed that the hypothetical precursor protein of japonicin-2Ja, as well as japonicin-1Ja and temporin-1Ja, is organized similarly to those of typical amphibian AMP precursors, with a highly conserved signal peptide, a relatively well conserved intervening sequence, and a hypervariable AMP mature region. Antimicrobial assays for synthetic replicates of cyclic and linear japonicin-2Ja revealed that the intramolecular disulfide bond is necessary for activity. A semi-quantitative analysis by real-time RTPCR using TaqMan probes revealed that the relative values of preprojaponicin-2Ja mRNA expression levels in the skin, skeletal muscle of hind leg, kidney, testis, small intestine, and stomach total RNA sample specimens in adult R. japonica were 6.5×10(5), 9.6, 2.0, 1.6, 1.6, and 1.0, respectively. The presence of preprojaponicin-2Ja mRNAs in the cytoplasm of glandular cells in R. japonica dorsal skin glands was demonstrated by means of in situ hybridization using digoxigenin-labeled cRNA probes for the precursor.