Defensins

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Naturally occurring antimicrobial cationic polypeptides play a major role in innate and adaptive immunity. These polypeptides are found to be either linear and unstructured or structured through disulfide bonds. Among the structured antimicrobial polypeptides, defensins comprise a family of cysteine-rich cationic polypeptides that contribute significantly to host defense against the invasion of microorganisms in animals, humans, insects and plants. Their wide-spread occurrence in various tissues of these diverse organisms, and their importance in innate and adaptive immunity have led to their identification, isolation and characterization. Much has also been published regarding their antimicrobial, antiviral and chemoattractive properties, and their molecular and cellular interactions.

Defensins

Federal government websites often end in. The site is secure. Endogenous antimicrobial peptides are widely distributed among vertebrates. They represent elements of a robust, ancestral animal immune system that predates the advent of lymphocytes and immunoglobulins. Secreted and cell-associated antimicrobial peptides enable their hosts to resist incursions by potential pathogens. From a pathogen's perspective, these peptides present a series of barriers to evade or overcome. In humans and other mammals , defensins and cathelicidins are the principal antimicrobial peptides of neutrophils and epithelial cells. Many mucosal surfaces are bathed by antimicrobial proteins, including lysozyme, lactoferrin, secretory leukoprotease inhibitor SLPI , and secretory phospholipase A2. Although the small intestinal Paneth cells of mice express at least 6 Ouellette et al. The generally conserved or invariant residues found in both subfamilies have been boxed. HBD-2, originally recovered from psoriatic skin Harder et al. In the epidermis, it is present in very low amounts unless induced by interleukin-1 IL-1 Liu et al. The HBD-3 gene was found by genomic searching Jia et al.

Mechanism of mammalian cell defensins mediated by peptide defensins. Hayashi, R.

Beta defensins are a family of vertebrate defensins. The beta defensins are antimicrobial peptides implicated in the resistance of epithelial surfaces to microbial colonization. Defensins are kDa, cationic, microbicidal peptides active against many Gram-negative and Gram-positive bacteria, fungi, and enveloped viruses, [1] containing three pairs of intramolecular disulfide bonds. On the basis of their size and pattern of disulfide bonding, mammalian defensins are classified into alpha , beta and theta categories. Every mammalian species explored thus far has beta-defensins. In cows, as many as 13 beta-defensins exist in neutrophils.

Nevertheless, big defensins underwent several independent gene loss events during animal evolution, being only retained in a limited number of phylogenetically distant invertebrates. Here, we explore the evolutionary history of this fascinating HDP family and investigate its patchy distribution in extant metazoans. We highlight the presence of big defensins in various classes of lophotrochozoans, as well as in a few arthropods and basal chordates amphioxus , mostly adapted to life in marine environments. Bivalve mollusks often display an expanded repertoire of big defensin sequences, which appear to be the product of independent lineage-specific gene tandem duplications, followed by a rapid molecular diversification of newly acquired gene copies. Moreover, big defensins follow different patterns of gene expression within a given species and respond differently to microbial challenges, suggesting functional divergence. Consistently, current structural data show that big defensin sequence diversity affects the 3D structure and biophysical properties of these polypeptides. Finally, we discuss the potential of big defensins as markers for animal health and for the nature-based design of novel therapeutics active at high salt concentrations.

Defensins

Defensins are a major family of host defense peptides expressed predominantly in neutrophils and epithelial cells. Their broad antimicrobial activities and multifaceted immunomodulatory functions have been extensively studied, cementing their role in innate immunity as a core host-protective component against bacterial, viral and fungal infections. This mini review summarizes the latest findings on the potential pathogenic properties of defensins against the backdrop of their protective roles in antiviral and antibacterial immunity.

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Schulz-Knappe P Forssmann W. Hoover, D. Therefore, it is of great research value for biomedical investigators to use defensins and their derived peptides as a basis to develop and test new therapeutics to treat both infectious and autoimmune diseases. Malcolm, J. Solomon, S. Internal factors that affect intestinal development include hormone homeostasis, nutrient metabolism, growth factors, and immune effectors. It should be noted that further confirmation of the potential therapeutic benefits of hBD1 is still lacking in transgenic animal studies and in vivo studies in primates. The reduced expression of cathelicidins first occurs in the crypts and lower villi and reaches the tip of the villi some days later. The second major task for the innate immune system is to activate an appropriate adaptive immune response against the invading organism. Neurath, M. Crohns Colitis 10 , — For example, by molecular dynamics simulations and by functional studies, it was found that hBD2 interacts with the CoVreceptor binding domain RBD and obstructs viral entrance of ACE2-expressing cells. Genomics 43 , — The structure, function and evolution of a complete human chromosome 8.

Naturally occurring antimicrobial cationic polypeptides play a major role in innate and adaptive immunity.

Ghosh, S. Biosynthesis of granule proteins in normal human bone marrow cells: Gelatinase is a marker of terminal neutrophil differentiation. Festschrift to highlight the career of Abba J. Intratumoral expression of mature human neutrophil peptide-1 mediates antitumor immunity in mice. Ryan, L. Multifunctionality may be a common attribute of other proteins involved in host defense. A cyclic antimicrobial peptide produced in primate leukocytes by the ligation of two truncated alpha-defensins. Awang, T. HNP1 also inhibits phagosomal escape and intracellular multiplication of Listeria monocytogenes and Mycobacterium tuberculosis in macrophages 86 , 87 , suggesting that the defensin, although not being expressed by macrophages, contributes to their antimicrobial function. Defensins are a major family of host defense peptides expressed predominantly in neutrophils and epithelial cells. Ji, J. An artificial human theta-defensin, [40] retrocyclin , was created by 'fixing' the pseudogene , and it was shown to be effective against HIV [41] and other viruses, including herpes simplex virus and influenza A. The C-terminal domain of SLPI residues 55— shows homology to the second domain of chelonianin, a basic protease inhibitor from Red Sea turtle, and is responsible for the molecule's prominent antiprotease activity Masuda et al. Canas, J.