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Gut Microbes 2010Recently, our laboratory demonstrated that Paneth cell defensins, innate antimicrobial peptides that contribute to mucosal host defense, are able to regulate the... (Review)
Review
Recently, our laboratory demonstrated that Paneth cell defensins, innate antimicrobial peptides that contribute to mucosal host defense, are able to regulate the composition of the intestinal bacterial microbiome. Using complementary mouse models of defensin deficiency (MMP7(-/-)) and surplus (HD5(+/+)), we noted defensin-dependent reciprocal shifts in the dominant bacterial species of the small intestine, without changes in total bacterial numbers. In addition, mice that expressed HD5 showed a significant loss of segemented filamentous bacteria (SFB), resulting in reduced numbers of Th17 cells in the lamina propria. This data showed a novel role for PC defensins in intestinal homeostasis, by regulation of the small intestinal microbiome. The microbiome plays an essential role in mediating host physiology, metabolism and immune response. The ability of PC defensins to regulate the composition of the biome suggests a much broader importance of these innate immune effectors than previously considered. In this addendum, the role of PC defensins in the regulation of the intestinal microbiome is reviewed, and discussed in the context of recent evidence that highlights the important role of PCs and defensins in the pathophysiology of inflammatory bowel disease.
Topics: Animals; Bacteria; Bacterial Load; Biodiversity; Defensins; Humans; Immunity, Mucosal; Intestine, Small; Metagenome; Mice; Mice, Knockout; Paneth Cells
PubMed: 21468224
DOI: 10.4161/gmic.1.6.14076 -
Journal of Virology Jun 2016Defensins are innate immune effector peptides expressed at mucosal surfaces throughout the human body and are potently antiviral in vitro The role of defensins in viral... (Review)
Review
Defensins are innate immune effector peptides expressed at mucosal surfaces throughout the human body and are potently antiviral in vitro The role of defensins in viral pathogenesis in vivo is poorly understood; however, recent studies have revealed that defensin-virus interactions in vivo are complicated and distinct from their proposed antiviral mechanisms in vitro These findings highlight the need for additional research that connects defensin neutralization of viruses in cell culture to in vivo antiviral mechanisms.
Topics: Animals; Antiviral Agents; Defensins; Humans; Immunomodulation; Mucous Membrane; Virus Diseases; Viruses; alpha-Defensins
PubMed: 27009960
DOI: 10.1128/JVI.00904-15 -
Acta Tropica Mar 2022Cecropins and defensins are the main classes of antimicrobial peptides in the mosquito innate immune system, acting against bacteria, fungi and protozoa. There is a...
Cecropins and defensins are the main classes of antimicrobial peptides in the mosquito innate immune system, acting against bacteria, fungi and protozoa. There is a knowledge gap concerning these peptide genes in anopheline mosquitoes from the Brazilian Amazon. Thus, this work aimed to describe molecular techniques for detecting the genes encoding the antimicrobial peptides cecropin A (CecA) and defensin in Anopheles darlingi mosquitoes and to perform molecular phylogeny of the sequenced genes using the maximum likelihood method and Bayesian inference with other species from different geographic areas. Our results show, for the first time, a molecular biology method for detecting CecA and defensin in Anopheles darlingi that allows for the use of these molecular markers for phylogenetic analysis in anopheline species, separating the species into single and monophyletic clades.
Topics: Animals; Anopheles; Antimicrobial Peptides; Bayes Theorem; Cecropins; Defensins; Phylogeny
PubMed: 34921765
DOI: 10.1016/j.actatropica.2021.106285 -
Analytical Chemistry Jan 2009Defensins are highly basic cationic peptides that are important components of the innate and adaptive immune response pathways. In addition, these peptides are involved...
Defensins are highly basic cationic peptides that are important components of the innate and adaptive immune response pathways. In addition, these peptides are involved in CD8+ T cell response to HIV-1, increased pulmonary infection risk among cystic fibrosis patients, upregulated levels of HNP-5 for patients with ulcerative colitis and Crohn's disease, and monitoring HNP-3 levels as a tumor classification scheme for cutaneous T cell lymphomas, and have promise in the pharmaceutical field as a new class of antibiotics. Here we present a parallel assay for the alpha (HNP1-3) and beta (HBD1-2) classes of defensins in saliva that are naturally observed in the concentration range of 1 ng/mL to 10 microg/mL. The method utilizes solid phase extraction of saliva samples combined with liquid chromatography-tandem mass spectrometry to identify and quantitate defensin targets. The approach involves limited sample manipulation and is easily amenable to automation. The saliva samples analyzed are derived from a large cohort study focused on examining the role of polymorphisms in genes of innate and adaptive immunity in modulating the response to vaccination for two gastrointestinal tract infections: typhoid and cholera. The alpha-defensin levels observed range from 1 to 10 microg/mL and correlate well with known active concentrations against a wide variety of pathogens. The observed concentration range for beta-defensins was between the detection limit and 33 ng/mL and had a sensitivity level that was comparable to immunoassay-based detection. This method is easily adapted for use in a clinical immunology setting and can be modified for other biological matrixes. This assay will facilitate examination of the production, secretion, and regulation of defensin peptides in a direct fashion to coordinate levels of these compounds with gender, age, response to vaccination, gene copy number, and oral health.
Topics: Amino Acid Sequence; Chromatography, Liquid; Cohort Studies; Defensins; Humans; Immunity, Cellular; Molecular Sequence Data; Saliva; Solid Phase Extraction; Tandem Mass Spectrometry; alpha-Defensins; beta-Defensins
PubMed: 19072583
DOI: 10.1021/ac801609r -
Journal of Internal Medicine Sep 2003Antibacterial peptides are the effector molecules of innate immunity. Generally they contain 15-45 amino acid residues and the net charge is positive. The cecropin type... (Review)
Review
Antibacterial peptides are the effector molecules of innate immunity. Generally they contain 15-45 amino acid residues and the net charge is positive. The cecropin type of linear peptides without cysteine were found first in insects, whilst the defensin type with three disulphide bridges were found in rabbit granulocytes. Now a database stores more than 800 sequences of antibacterial peptides and proteins from the animal and plant kingdoms. Generally, each species has 15-40 peptides made from genes, which code for only one precursor. The dominating targets are bacterial membranes and the killing reaction must be faster than the growth rate of the bacteria. Some antibacterial peptides are clearly multifunctional and an attempt to predict this property from the hydrophobicity of all amino acid side chains are given. Gene structures and biosynthesis are known both in the fruit fly Drosophila and several mammals. Humans need two classes of defensins and the cathelicidin-derived linear peptide LL-37. Clinical cases show that deficiencies in these peptides give severe symptoms. Examples given are morbus Kostmann and atopic allergy. Several antibacterial peptides are being developed as drugs.
Topics: Animals; Animals, Domestic; Antimicrobial Cationic Peptides; Anura; Bacterial Infections; Blood Proteins; Cloning, Molecular; DNA, Complementary; Defensins; Drosophila melanogaster; Humans; Immunity, Innate; Insect Hormones; Mice; Up-Regulation
PubMed: 12930229
DOI: 10.1046/j.1365-2796.2003.01228.x -
Molecules (Basel, Switzerland) Jul 2017Cyclic peptides are receiving significant attention thanks to their antimicrobial activity and high serum stability, which is useful to develop and design novel... (Review)
Review
Cyclic peptides are receiving significant attention thanks to their antimicrobial activity and high serum stability, which is useful to develop and design novel antimicrobial agents. Antimicrobial peptides appear to be key components of innate defences against bacteria, viruses, and fungi. Among the others, defensins possess a strong microbicidial activity. Defensins are cationic and amphipathic peptides with six cysteine residues connected by three disulfide bonds found in plants, insects, and mammals; they are divided in three families: α-, β-, and θ-defensins. α-Defensins are contained in the primary granules of human neutrophils; β-defensins are expressed in human epithelia; and θ-defensins are pseudo-cyclic defensins not found in humans, but in rhesus macaques. The structural diversities among the three families are reflected in a different antimicrobial action as well as in serum stability. The engineering of these peptides is an exciting opportunity to obtain more functional antimicrobial molecules highlighting their potential as therapeutic agents. The present review reports the most recent advances in the field of cyclic peptides with a specific regard to defensin analogs.
Topics: Animals; Anti-Bacterial Agents; Anti-Infective Agents; Bacteria; Defensins; Humans; Macaca mulatta; Neutrophils; Peptides, Cyclic; Viruses; beta-Defensins
PubMed: 28726740
DOI: 10.3390/molecules22071217 -
Peptides Feb 2022Immunomodulatory peptides are a complex class of bioactive peptides that encompasses substances with different mechanisms of action. Immunomodulatory peptides could also... (Review)
Review
Immunomodulatory peptides are a complex class of bioactive peptides that encompasses substances with different mechanisms of action. Immunomodulatory peptides could also be used in vaccines as adjuvants which would be extremely desirable, especially in response to pandemics. Thus, immunomodulatory peptides in food of plant origin could be regarded both as valuable suplements of novel functional food preparation and/or as precursors or possible active ingredients for drugs design for treatment variety of conditions arising from impaired function of immune system. Given variety of mechanisms, different tests are required to assess effects of immunomodulatory peptides. Some of those effects show good correlation with in vivo results but others, less so. Certain plant peptides, such as defensins, show both immunomodulatory and antimicrobial effect, which makes them interesting candidates for preparation of functional food and feed, as well as templates for design of synthetic peptides.
Topics: Defensins; Drug Discovery; Functional Food; Humans; Immunomodulation; Peptides; Plant Proteins
PubMed: 34856531
DOI: 10.1016/j.peptides.2021.170696 -
BMC Genomics Apr 2017β-defensins are small, cationic, antimicrobial peptides found in species across the plant and animal kingdoms. In addition to microbiocidal activity, roles in immunity... (Comparative Study)
Comparative Study
BACKGROUND
β-defensins are small, cationic, antimicrobial peptides found in species across the plant and animal kingdoms. In addition to microbiocidal activity, roles in immunity as well as reproduction have more recently been documented. β-defensin genes in Ovis aries (domestic sheep) have been poorly annotated, having been identified only by automatic gene prediction algorithms. The objective of this study was to use a comparative genomics approach to identify and characterise the β-defensin gene repertoire in sheep using the bovine genome as the primary reference.
RESULTS
All 57 currently predicted bovine β-defensin genes were used to find orthologous sequences in the most recent version of the sheep genome (OAR v4.0). Forty three genes were found to have close genomic matches (>70% similarity) between sheep and cattle. The orthologous genes were located in four clusters across the genome, with 4 genes on chromosome 2, 19 genes on chromosome 13, 5 genes on chromosome 20 and 15 genes on chromosome 26. Conserved gene order for the β-defensin genes was apparent in the two smaller clusters, although gene order was reversed on chromosome 2, suggesting an inversion between sheep and cattle. Complete conservation of gene order was also observed for chromosome 13 β-defensin orthologs. More structural differences were apparent between chromosome 26 genes and the orthologous region in the bovine reference genome, which is known to be copy-number variable. In this cluster, the Defensin-beta 1 (DEFB1) gene matched to eleven Bovine Neutrophil beta-Defensin (BNBD) genes on chromosome 27 with almost uniform similarity, as well as to tracheal, enteric and lingual anti-microbial peptides (TAP, EAP and LAP), suggesting that annotation of the bovine reference sequence is still incomplete. qPCR was used to profile the expression of 34 β-defensin genes, representing each of the four clusters, in the ram reproductive tract. Distinct site-specific and differential expression profiles were detected across the reproductive tract of mature rams with preferential β-defensin gene expression in the epididymis, recapitulating observations for orthologous genes in other species.
CONCLUSIONS
This is the first comprehensive analysis of β-defensin genes encoded by the ovine reference sequence, and the first report of an expanded repertoire of β-defensin genes in this species. The preferential expression of these genes in the epididymis suggests a role in fertility, possibly providing immunoprotection for sperm within the female reproductive tract.
Topics: Amino Acid Sequence; Animals; Chromosome Mapping; Gene Expression; Male; Multigene Family; Phylogeny; Sequence Analysis, DNA; Sheep, Domestic; Testis; beta-Defensins
PubMed: 28376793
DOI: 10.1186/s12864-017-3666-x -
PloS One 2020Plant defensins possess diverse biological functions that include antifungal and antibacterial activities and α-amylase and trypsin inhibitory properties. Two...
Plant defensins possess diverse biological functions that include antifungal and antibacterial activities and α-amylase and trypsin inhibitory properties. Two mutations, G9R and V39R, were confirmed to increase the antifungal activity of Raphanus sativus antifungal protein 2 (RsAFP2). Accelerated Molecular Dynamics (aMD) were carried out to examine the conformational changes present in these RsAFP2 mutants, and its two closest homologs compared to the wild-type protein. Specifically, the root mean square fluctuation values for the eight cysteine amino acids involved in the four disulfide bonds were low in the V39R mutant compared to the wild-type. Additionally, analysis of the free energy change revealed that G9R and V39R mutations exert a neutral and stabilizing effect on RsAFP2 conformation, and this is supported by the observed lower total energy of mutants compared to the wild-type, suggesting that enhanced stability of the mutants. However, MD simulations to a longer time scale would aid in capturing more conformational state of the wild-type and mutants defensin protein. Furthermore, the aMD simulations on fungal mimic membranes with RsAFP2 and its mutants and homologs showed that the mutant proteins caused higher deformation and water diffusion than the native RsAFP2, especially the V39R mutant. The mutant variants seem to interact by specifically targeting the POPC and POPI lipids amongst others. This work highlights the stabilizing effect of mutations at the 9th and 39th positions of RsAFP2 and their increased membrane deformation activity.
Topics: Amino Acid Sequence; Defensins; Deuterium; Molecular Dynamics Simulation; Molecular Sequence Data; Mutation; Sequence Alignment; Sequence Homology, Amino Acid
PubMed: 33253167
DOI: 10.1371/journal.pone.0241679 -
Infection and Immunity Jun 2014Mammalian α-defensins are approximately 4- to 5-kDa broad-spectrum antimicrobial peptides and abundant granule constituents of neutrophils and small intestinal Paneth...
Mammalian α-defensins are approximately 4- to 5-kDa broad-spectrum antimicrobial peptides and abundant granule constituents of neutrophils and small intestinal Paneth cells. The bactericidal activities of amphipathic α-defensins depend in part on electropositive charge and on hydrophobic amino acids that enable membrane disruption by interactions with phospholipid acyl chains. Alignment of α-defensin primary structures identified conserved hydrophobic residues in the loop formed by the Cys(III)-Cys(V) disulfide bond, and we have studied their role by testing the effects of mutagenesis on bactericidal activities. Mouse α-defensin 4 (Crp-4) and rhesus myeloid α-defensin 4 (RMAD-4) were selected for these studies, because they are highly bactericidal in vitro and have the same overall electropositive charge. Elimination of hydrophobicity by site-directed mutagenesis at those positions in Crp-4 attenuated bactericidal activity markedly. In contrast to native Crp-4, the (I23/F25/L26/G)-Crp-4 variant lacked bactericidal activity against Salmonella enterica serovar Typhimurium and did not permeabilize Escherichia coli ML35 cells as a result of removing aliphatic side chains by Gly substitutions. Ala replacements in (I23/F25/L26/A)-Crp-4 restored activity, evidence that hydrophobicity contributed by Ala methyl R-groups was sufficient for activity. In macaques, neutrophil α-defensin RMAD-6 is identical to RMAD-4, except for a F28S difference, and (F28S)-RMAD-4 mutagenesis attenuated RMAD-4 bactericidal activity and E. coli permeabilization. Interestingly, (R31/32D)-Crp-4 lacks activity in these assays despite the presence of the Ile23, Phe25, and Leu26 hydrophobic patch. We infer that electrostatic interactions between cationic α-defensin residues and negative charge on bacteria precede interactions between critical hydrophobic residue positions that mediate membrane disruption and bacterial cell killing.
Topics: Amino Acid Substitution; Animals; Bacteria; Cell Membrane Permeability; Cells, Cultured; Hydrophobic and Hydrophilic Interactions; Macaca mulatta; Mice; Mutagenesis, Site-Directed; Recombinant Proteins; alpha-Defensins
PubMed: 24614658
DOI: 10.1128/IAI.01414-13