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Methods in Molecular Biology (Clifton,... 2017Computational prediction and design of membrane protein-protein interactions facilitate biomedical engineering and biotechnological applications. Due to their...
Computational prediction and design of membrane protein-protein interactions facilitate biomedical engineering and biotechnological applications. Due to their antimicrobial activity, human defensins play an important role in the innate immune system. Human defensins are attractive pharmaceutical targets due to their small size, broad activity spectrum, reduced immunogenicity, and resistance to proteolysis. Protein engineering based modification of defensins can improve their pharmaceutical properties. Here we present an approach to computationally probe defensins' oligomerization states in the membrane. First, we develop a novel docking and rescoring algorithm. Then, on the basis of the 3D structure of Sapecin, an insect defensin, and a model of its antimicrobial ion-channel, we optimize the parameters of our empirical scoring function. Finally, we apply our docking program and scoring function to the hBD-2 (human β-defensin-2) molecule and obtain structures of four possible oligomers. These results can be used in higher level simulations.
Topics: Defensins; Humans; Membrane Proteins; Models, Molecular; Molecular Docking Simulation; Molecular Dynamics Simulation; Protein Binding; Protein Conformation; Protein Multimerization
PubMed: 27914061
DOI: 10.1007/978-1-4939-6637-0_18 -
Plant Physiology Jan 2023Grain cadmium (Cd) is translocated from source to sink tissues exclusively via phloem, though the phloem Cd unloading transporter has not been identified yet. Here, we...
Grain cadmium (Cd) is translocated from source to sink tissues exclusively via phloem, though the phloem Cd unloading transporter has not been identified yet. Here, we isolated and functionally characterized a defensin-like gene DEFENSIN 8 (DEF8) highly expressed in rice (Oryza sativa) grains and induced by Cd exposure in seedling roots. Histochemical analysis and subcellular localization detected DEF8 expression preferentially in pericycle cells and phloem of seedling roots, as well as in phloem of grain vasculatures. Further analysis demonstrated that DEF8 is secreted into extracellular spaces possibly by vesicle trafficking. DEF8 bound to Cd in vitro, and Cd efflux from protoplasts as well as loading into xylem vessels decreased in the def8 mutant seedlings compared with the wild type. At maturity, significantly less Cd accumulation was observed in the mutant grains. These results suggest that DEF8 is a dual function protein that facilitates Cd loading into xylem and unloading from phloem, thus mediating Cd translocation from roots to shoots and further allocation to grains, representing a phloem Cd unloading regulator. Moreover, essential mineral nutrient accumulation as well as important agronomic traits were not affected in the def8 mutants, suggesting DEF8 is an ideal target for breeding low grain Cd rice.
Topics: Cadmium; Oryza; Phloem; Plant Breeding; Edible Grain; Seedlings; Plant Roots; Defensins
PubMed: 36087013
DOI: 10.1093/plphys/kiac423 -
Journal of Virology Apr 2022Fecal-oral pathogens encounter constitutively expressed enteric alpha-defensins in the intestine during replication and transmission. Alpha-defensins can be potently...
Fecal-oral pathogens encounter constitutively expressed enteric alpha-defensins in the intestine during replication and transmission. Alpha-defensins can be potently antiviral and antibacterial; however, their primary sequences, the number of isoforms, and their activity against specific microorganisms often vary greatly between species, reflecting adaptation to species-specific pathogens. Therefore, alpha-defensins might influence not only microbial evolution and tissue tropism within a host but also species tropism and zoonotic potential. To investigate these concepts, we generated a panel of enteric and myeloid alpha-defensins from humans, rhesus macaques, and mice and tested their activity against group A rotaviruses, an important enteric viral pathogen of humans and animals. Rotaviral adaptation to the rhesus macaque correlated with resistance to rhesus enteric, but not myeloid, alpha-defensins and sensitivity to human alpha-defensins. While mouse rotaviral infection was increased in the presence of mouse enteric alpha-defensins, two prominent genotypes of human rotaviruses were differentially sensitive to human enteric alpha-defensins. Furthermore, the effects of cross-species alpha-defensins on human and mouse rotaviruses did not follow an obvious pattern. Thus, exposure to alpha-defensins may have shaped the evolution of some, but not all, rotaviruses. We then used a genetic approach to identify the viral attachment and penetration protein, VP4, as a determinant of alpha-defensin sensitivity. Our results provide a foundation for future studies of the VP4-dependent mechanism of defensin neutralization, highlight the species-specific activities of alpha-defensins, and focus future efforts on a broader range of rotaviruses that differ in VP4 to uncover the potential for enteric alpha-defensins to influence species tropism. Rotavirus is a leading cause of severe diarrhea in young children. Like other fecal-oral pathogens, rotaviruses encounter abundant, constitutively expressed defensins in the small intestine. These peptides are a vital part of the vertebrate innate immune system. By investigating the impact that defensins from multiple species have on the infectivity of different strains of rotavirus, we show that some rotaviral infections can be inhibited by defensins. We also found that some, but not all, rotaviruses may have evolved resistance to defensins in the intestine of their host species, and some even appropriate defensins to increase their infectivity. Because rotaviruses infect a broad range of animals and rotaviral infections are highly prevalent in children, identifying immune defenses against infection and how they vary across species and among viral genotypes is important for our understanding of the evolution, transmission, and zoonotic potential of these viruses as well as the improvement of vaccines.
Topics: Animals; Humans; Intestine, Small; Macaca mulatta; Mice; Rotavirus; Rotavirus Infections; Viral Structural Proteins; alpha-Defensins
PubMed: 35285683
DOI: 10.1128/jvi.02053-21 -
Plant Physiology Jan 2023
Topics: Humans; Cadmium; Oryza; Phloem; Metals, Heavy; Seeds; Defensins; Soil Pollutants
PubMed: 36222568
DOI: 10.1093/plphys/kiac475 -
Biomedicine & Pharmacotherapy =... Nov 2022Diabetic wound, one of the most common serious complications of diabetic patients, is an important factor in disability and death. Much of the research on the... (Review)
Review
Diabetic wound, one of the most common serious complications of diabetic patients, is an important factor in disability and death. Much of the research on the pathophysiology of diabetic wound healing has long focused on mechanisms mediated by hyperglycemia, chronic inflammation, microcirculatory and macrocirculatory dysfunction. However, recent evidence suggests that defensins may play a crucial role in the development and perpetuation of diabetic wound healing. The available findings suggest that defensins exert a beneficial influence on diabetic wound healing through antimicrobial, immunomodulatory, angiogenic, tissue regenerator effects, and insulin resistance improvement. Therefore, summarizing the existing research progress on defensins in the diabetic wound may present a promising strategy for diabetic patients.
Topics: Humans; Microcirculation; Wound Healing; Anti-Infective Agents; Diabetes Mellitus; Defensins
PubMed: 36099789
DOI: 10.1016/j.biopha.2022.113694 -
Journal of UOEH 2020The distinction between bacterial infectious and noninfectious arthritis is typically challenging in the early stages; however, it is critical for treatment decision...
The distinction between bacterial infectious and noninfectious arthritis is typically challenging in the early stages; however, it is critical for treatment decision making. Here, we investigated the diagnostic relevance of alpha- and beta-defensin levels in serum and synovial fluid as biomarkers of joint infection in patients presenting with fever and arthritis. The study included 12 patients who presented with fever (≥37°C) and arthritis (pain in the knee or hip joint). The diagnostic criteria for periprosthetic joint infection proposed by the Musculoskeletal Infection Society were used to detect joint infection and categorize the patients into infection and non-infection groups. Alpha-defensin-1 and beta-defensin-3 levels in serum and synovial fluid were measured using enzyme-linked immunosorbent assay. No significant between-group difference was observed with respect to serum alpha-defensin-1 levels; however, synovial fluid alpha-defensin-1 levels were significantly higher in the infection group (33.6 ± 26.2 ng/ml) than in the non-infection group (0.9 ± 0.4 ng/ml). No significant between-group differences were observed with respect to serum or synovial fluid beta-defensin-3 levels. Furthermore, synovial fluid alpha-defensin-1 levels were increased in patients without prosthesis in the infection group. In conclusion, in patients with fever and arthritis, synovial fluid alpha-defensin-1 levels were significantly higher in patients with infectious arthritis than in those with noninfectious arthritis. Therefore, synovial fluid alpha-defensin-1 levels is a useful diagnostic marker for joint infection.
Topics: Arthritis; Biomarkers; Humans; Synovial Fluid; alpha-Defensins
PubMed: 32507840
DOI: 10.7888/juoeh.42.167 -
Current Protein & Peptide Science 2017Defensins are a superfamily of antimicrobial peptides, present in vertebrates, invertebrates, fungi and plants, suggesting that they appeared prior to the divergence in... (Review)
Review
Defensins are a superfamily of antimicrobial peptides, present in vertebrates, invertebrates, fungi and plants, suggesting that they appeared prior to the divergence in eukaryotes. The destitution of toxicity to mammalian cells of plant defensins has led to a new research ground, i.e., their potential medical use against human infectious diseases. Isolating defensins from natural sources, like plant tissues, can be time-consuming, labor intensive and usually present low yields. Strategies for large-scale production of purified active defensins have been employed using heterologous expression systems (HES) for defensin production, usually based in E. coli system. Like any other technology, HES present limitations and drawbacks demanding a careful experimental design prior the system selection. This review is proposed to discuss some of the major concerns when choosing to heterologously express plant defensins, with special attention on bacterial expression systems.
Topics: Anti-Infective Agents; Cloning, Molecular; Databases, Genetic; Defensins; Escherichia coli; Gene Expression; Genetic Vectors; Inclusion Bodies; Pichia; Plant Proteins; Plants; Protein Folding; Recombinant Proteins; Reverse Genetics
PubMed: 27356942
DOI: 10.2174/1389203717666160625070414 -
Accounts of Chemical Research Apr 2017Human α-defensin 6 (HD6) is a 32-residue cysteine-rich peptide that contributes to innate immunity by protecting the host at mucosal sites. This peptide is produced in... (Review)
Review
Human α-defensin 6 (HD6) is a 32-residue cysteine-rich peptide that contributes to innate immunity by protecting the host at mucosal sites. This peptide is produced in small intestinal Paneth cells, stored as an 81-residue precursor peptide named proHD6 in granules, and released into the lumen. One unusual feature of HD6 is that it lacks the broad-spectrum antimicrobial activity observed for other human α-defensins, including the Paneth cell peptide human α-defensin 5 (HD5). HD6 exhibits unprecedented self-assembly properties, which confer an unusual host-defense function. HD6 monomers self-assemble into higher-order oligomers termed "nanonets", which entrap microbes and prevent invasive gastrointestinal pathogens such as Salmonella enterica serovar Typhimurium and Listeria monocytogenes from entering host cells. One possible advantage of this host-defense mechanism is that HD6 helps to keep microbes in the lumen such that they can be excreted or attacked by other components of the immune system, such as recruited neutrophils. In this Account, we report our current understanding of HD6 and focus on work published since 2012 when Bevins and co-workers described the discovery of HD6 nanonets in the literature. First, we present studies that address the biosynthesis, storage, and maturation of HD6, which demonstrate that nature uses a propeptide strategy to spatially and temporally control the formation of HD6 nanonets in the small intestine. The propeptide is stored in Paneth cell granules, and proteolysis occurs during or following release into the lumen, which affords the 32-residue mature peptide that self-assembles. We subsequently highlight structure-function studies that provide a foundation for understanding the molecular basis for why HD6 exhibits unusual self-assembly properties compared with other characterized defensins. The disposition of hydrophobic residues in the HD6 primary structure differs from that of other human α-defensins and is an important structural determinant for oligomerization. Lastly, we consider functional studies that illuminate how HD6 contributes to mucosal immunity. We recently discovered that in addition to blocking bacterial invasion into host epithelial cells by Gram-negative and Gram-positive gastrointestinal pathogens, HD6 suppresses virulence traits displayed by the opportunistic human fungal pathogen Candida albicans. In particular, we found that C. albicans biofilm formation, which causes complications in the treatment of candidiasis, is inhibited by HD6. This observation suggests that HD6 may contribute to intestinal homeostasis by helping to keep C. albicans in its commensal state. We intend for this Account to inspire further biochemical, biophysical, and biological investigations that will advance our understanding of HD6 in mucosal immunity and the host-microbe interaction.
Topics: Fungi; Gram-Negative Bacteria; Gram-Positive Bacteria; Humans; Immunity, Innate; alpha-Defensins
PubMed: 28296382
DOI: 10.1021/acs.accounts.6b00653 -
Indian Journal of Dental Research :... 2015Defensins are abundant and widely distributed peptides in human and animal tissues that are involved in host defence. Defensins not only have the ability to strengthen... (Review)
Review
Defensins are abundant and widely distributed peptides in human and animal tissues that are involved in host defence. Defensins not only have the ability to strengthen the innate immune system but can also enhance the adaptive immune system by chemotaxis of monocytes, T-lymphocytes, dendritic cells and mast cells to the infection site. Defensins also improves the capacity of macrophage phagocytosis. A greater understanding of how these peptides act in the healthy, gingivitis and periodontitis conditions would definitely open new opportunities for identification, prevention and treatment of periodontal diseases. This discussion focuses on recent studies about biological function of defensins in human diseases and animal models.
Topics: Adaptive Immunity; Animals; Defensins; Humans; Immunity, Innate; Periodontal Diseases
PubMed: 26481877
DOI: 10.4103/0970-9290.167627 -
Biological & Pharmaceutical Bulletin 2021α-Defensin 5 has a particularly broad antibacterial spectrum; it eliminates pathogenic microorganisms and regulates intestinal flora. Although Caco-2 cells are similar... (Comparative Study)
Comparative Study
α-Defensin 5 has a particularly broad antibacterial spectrum; it eliminates pathogenic microorganisms and regulates intestinal flora. Although Caco-2 cells are similar to small intestinal cells, it is unclear whether they secrete α-defensin 5. Therefore, we investigated whether Caco-2 cells secrete α-defensin 5 and determined the secretion mechanism using cells from three cell banks (ATCC, DSMZ, and RIKEN). The Caco-2 cell proliferation rate increased with the number of culture days, irrespective of cell bank origin. On the other hand, the alkaline phosphatase activity, which affects cell differentiation and the mRNA levels of several cytokines, such as interleukin 8 (IL-8), IL-6, IL-1β, tumor necrosis factor-α (TNF-α), and IL-2, in the Caco-2 cells fluctuated with the number of culture days, and differed for each cell bank. α-Defensin 5 secretion was detected in all three cell bank Caco-2 cells; particularly, the ATCC Caco-2 cells grew linearly depending on the cell culture day as well as the levels of IL-8 and TNF-α mRNA. This suggested that α-defensin 5 secretion in the ATCC Caco-2 cells was associated with fluctuations in the mRNA levels of various cytokines, such as IL-8 and TNF-α. In conclusion, Caco-2 cells may be a simple model for screening health food components and drugs that affect α-defensin 5 secretion.
Topics: Biological Specimen Banks; Caco-2 Cells; Cell Proliferation; Cytokines; Drug Evaluation, Preclinical; Feasibility Studies; Humans; Reproducibility of Results; alpha-Defensins
PubMed: 33518681
DOI: 10.1248/bpb.b20-00644