Evolution of duplications in the transferrin family of proteins

The role of TF-b in iron homeostasis and bacterial defense in common carp (Cyprinus carpio)

Transferrin (TF) is a prototypical biological macromolecule protein known for its iron-binding properties. TF proteins play a crucial role in modulating host iron homeostasis and defending against pathogen invasion. In this study, we utilized common carp (Cyprinus carpio) tissues and Epithelioma papulosum cyprinid (EPC) cells to establish experimental models of iron overload with FeCl3 or ferric amine citrate (FAC), and to establish experimental models of bacterial infection with Aeromonas hydrophila. The current research has successfully identified the CcTF-b gene in common carp, revealing an ORF of 2001 bp with N-terminal and C-terminal structures. CcTF-b exhibited inhibitory effects on the growth of LPS and LTA in vitro. In the experimental models, the upregulations of PTGS2a and PTGS2a-like mRNA and protein levels were observed. Overexpression or interference with CcTF-b levels can modulate the expression of ferroptosis-related genes, inflammatory cytokines, lipid reactive oxygen species, GSH/GSSH levels, and Fe2+ concentration. Significantly, the expression levels of Nrf2 and GPX4 mRNA and protein, as well as the bacterial load of A. hydrophila, could be also modulated either by upregulating or downregulating CcTF-b factors. In conclusion, in this study, these findings suggest that CcTF-b plays a critical role in the innate immune response of common carp.

Simultaneous determination of inflammatory factors SAA and LTF based on stable element labeling and inductively coupled plasma mass spectrometry to aid in the diagnosis of infection

OBJECTIVE

The clinical value of Serum amyloid A (SAA) and Lactoferrin (LTF) has received significant attention, but their detection methods are inadequate, which limits their application. This study aims to develop a dual detection method based on stable element labeling strategies and inductively coupled plasma mass spectrometry (ICP-MS) for SAA/LTF and to assess whether it can be widely used in clinical practice.

METHODS

A duplex immunoassay system based on sandwich method was constructed. After optimization, methodological evaluation was performed with the guidelines of Clinical Laboratory Standards Institute (CLSI). Finally, 131 plasma samples were collected to analyze whether the new method is suitable for clinical detection.

RESULTS

The LoB, LLoQ, ULoQ, and linear range of the assay were 1.09 ng/mL, 3 ng/mL, 1500 ng/mL, 3-1500 ng/mL for SAA and 0.85 ng/mL, 2 ng/mL, 1200 ng/mL, 2-1200 ng/mL for LTF respectively. The recovery rates were 95.01% to 106.26%, the intra-batch precision of low, intermediate, and high-level samples was <8%, and the inter-batch of them was <11%, the deviation of interference test results was less than±10%. The Area Under the Curve (AUC) was 0.9809 for SAA, 0.8599 for LTF, and 0.9986 for combination.

CONCLUSION

The quantitative duplex immunoassay for SAA/LTF has high accuracy, good precision, and high specificity, which meets the clinical testing requirements and can be widely used in clinical practice.

de B. Pereira H, M. da Rocha Filho T, A. S. Machado B, A. Moret M. New distance measure for comparing protein using cellular automata image

One of the first steps in protein sequence analysis is comparing sequences to look for similarities. We propose an information theoretical distance to compare cellular automata representing protein sequences, and determine similarities. Our approach relies in a stationary Hamming distance for the evolution of the automata according to a properly chosen rule, and to build a pairwise similarity matrix and determine common ancestors among different species in a simpler and less computationally demanding computer codes when compared to other methods.

Testing Antimicrobial Properties of Human Lactoferrin-Derived Fragments

Lactoferrin, an iron-binding glycoprotein, plays a significant role in the innate immune system, with antibacterial, antivirial, antifungal, anticancer, antioxidant and immunomodulatory functions reported. It is worth emphasizing that not only the whole protein but also its derived fragments possess antimicrobial peptide (AMP) activity. Using AmpGram, a top-performing AMP classifier, we generated three novel human lactoferrin (hLF) fragments: hLF 397-412, hLF 448-464 and hLF 668-683, predicted with high probability as AMPs. For comparative studies, we included hLF 1-11, previously confirmed to kill some bacteria. With the four peptides, we treated three Gram-negative and three Gram-positive bacterial strains. Our results indicate that none of the three new lactoferrin fragments have antimicrobial properties for the bacteria tested, but hLF 1-11 was lethal against Pseudomonas aeruginosa. The addition of serine protease inhibitors with the hLF fragments did not enhance their activity, except for hLF 1-11 against P. aeruginosa, which MIC dropped from 128 to 64 µg/mL. Furthermore, we investigated the impact of EDTA with/without serine protease inhibitors and the hLF peptides on selected bacteria. We stress the importance of reporting non-AMP sequences for the development of next-generation AMP prediction models, which suffer from the lack of experimentally validated negative dataset for training and benchmarking.

Comparative study on the interaction between transferrin and flavonols: Experimental and computational modeling approaches

Transferrin is the indispensable component in the body fluids and has been explored as a potential drug carrier for target drugs to cancer cells. Flavonols are widely distributed in plants and shown a wide range of biological activities. In the present study, the interaction between flavonols (including galangin, kaempferol, quercetin, and myricetin) and transferrin under physiological conditions was investigated by using experimental as well as computational approaches. Fluorescence data reveal that the fluorescence quenching mechanism of transferrin by flavonols is static quenching. Transferrin has moderate affinity with flavonols, and the binding constants (K_a) are 10³-10⁴ L/mol. In addition, there are two different binding sites for the interaction between kaempferol and transferrin. Thermodynamic parameter analysis shows that the interaction of flavonols and transferrin is synergistically driven by enthalpy and entropy. Hydrophobic interaction, electrostatic force and hydrogen bonds are the main force types. Synchronous fluorescence spectroscopy shows that flavonols decrease the hydrophobicity of the microenvironment around tryptophan (Trp) and have no effect on the microenvironment around tyrosine (Tyr). UV-vis and CD spectra show that the interaction between transferrin and flavonols leads to the loosening and unfolding of transferrin backbone. The increase of β-sheet is accompanied by the decrease of α-helix and β-turn. The specific binding sites of flavonols to transferrin are confirmed by molecular docking. Molecular dynamic simulation suggests that the transferrin-flavonols docked complex is stable throughout the simulation trajectory.

Insights from targeting transferrin receptors to develop vaccines for pathogens of humans and food production animals

While developing vaccines targeting surface transferrin receptor proteins in Gram-negative pathogens of humans and food production animals, the common features derived from their evolutionary origins has provided us with insights on how improvements could be implemented in the various stages of research and vaccine development. These pathogens are adapted to live exclusively on the mucosal surfaces of the upper respiratory or genitourinary tract of their host and rely on their receptors to acquire iron from transferrin for survival, indicating that there likely are common mechanisms for delivering transferrin to the mucosal surfaces that should be explored. The modern-day receptors are derived from those present in bacteria that lived over 320 million years ago. The pathogens represent the most host adapted members of their bacterial lineages and may possess factors that enable them to have strong association with the mucosal epithelial cells, thus likely reside in a different niche than the commensal members of the bacterial lineage. The bacterial pathogens normally lead a commensal lifestyle which presents challenges for development of relevant infection models as most infection models either exclude the early stages of colonization or subsequent disease development, and the immune mechanisms at the mucosal surface that would prevent disease are not evident. Development of infection models emulating natural horizontal disease transmission are also lacking. Our aim is to share our insights from the study of pathogens of humans and food production animals with individuals involved in vaccine development, maintaining health or regulation of products in the human and animal health sectors.

The application of lactoferrin in infant formula: The past, present and future

Human milk is universally regarded as the gold standard to fulfill nutrition needs of infants. Lactoferrin (LF) is a major multiple bioactive glycoprotein in human milk but little is presented in infant formula. LF can resist digestion in the infant gastrointestinal tract and is absorbed into the bloodstream in an intact form to perform physiological functions. Evidence suggest that LF prevents pathogen infection, promotes immune system development, intestinal development, brain development and bone health, as well as ameliorates iron deficiency anemia. However, more clinical studies of LF need to be further elucidated to determine an appropriate dosage for application in infant formula. LF is sensitive to denaturation induced by processing of infant formula such as heat treatments and spay drying. Thus, further studies should be focus on maximizing the retention of LF activity in the infant formula process. This review summarizes the structural features of LF. Then the digestion, absorption and metabolism of LF in infants are discussed, followed by the function of LF for infants. Further, we summarize LF in infant formula and effects of processing of infant formula on bioactivities of LF, as well as future perspectives of LF research.

Functional Divergence of the N-Lobe and C-Lobe of Transferrin Gene in Pungitius sinensis (Amur Stickleback)

Transferrin is an important iron-binding glycosylated protein and plays key roles in iron-binding and immune response. Here, a 2037-bp open reading frame was obtained from our previous transcriptome sequencing data of Amur stickleback, which encoded a 679 amino acid putative transferrin protein harbored obvious N-lobe and C-lobe domains. The tissue-specific expression pattern showed that the transcript was detected in a variety of tissues, with the highest signal in liver. Moreover, Streptococcus iniae pathogen stimulation can increase the expression level of this transcript, implying important immune properties for organisms. Next, N-lobes and C-lobes were obtained from 45 fish species. The phylogenetic tree showed that N-lobes and C-lobes were in two different evolutionary branches, and they had different motif composition. Functional divergence indicated a higher evolutionary rate or site-specific alteration among the N-lobe and C-lobe groups. Ka/Ks value of C-lobe group was relatively higher than that of N-lobe group, indicating a faster change rate of C-lobe sequences in evolution. Moreover, some sites experiencing positive selection were also found, which may be involved in the iron- or anion-binding, pathogen resistance and diversification of transferrin protein. Differential iron-binding activity was also detected between N-lobe and C-lobe of Amur stickleback transferrin protein with Chrome Azurol S assay. Compared with the C-lobe, the N-lobe showed stronger growth inhibitory activity of Escherichia coli, implying their potential antibacterial properties. This study will give a reference for subsequent research of transferrin proteins.

Structural and functional insights into iron acquisition from lactoferrin and transferrin in Gram-negative bacterial pathogens

Iron is an essential element for various lifeforms but is largely insoluble due to the oxygenation of Earth’s atmosphere and oceans during the Proterozoic era. Metazoans evolved iron transport glycoproteins, like transferrin (Tf) and lactoferrin (Lf), to keep iron in a non-toxic, usable form, while maintaining a low free iron concentration in the body that is unable to sustain bacterial growth. To survive on the mucosal surfaces of the human respiratory tract where it exclusively resides, the Gram-negative bacterial pathogen Moraxella catarrhalis utilizes surface receptors for acquiring iron directly from human Tf and Lf. The receptors are comprised of a surface lipoprotein to capture iron-loaded Tf or Lf and deliver it to a TonB-dependent transporter (TBDT) for removal of iron and transport across the outer membrane. The subsequent transport of iron into the cell is normally mediated by a periplasmic iron-binding protein and inner membrane transport complex, which has yet to be determined for Moraxella catarrhalis. We identified two potential periplasm to cytoplasm transport systems and performed structural and functional studies with the periplasmic binding proteins (FbpA and AfeA) to evaluate their role. Growth studies with strains deleted in the fbpA or afeA gene demonstrated that FbpA, but not AfeA, was required for growth on human Tf or Lf. The crystal structure of FbpA with bound iron in the open conformation was obtained, identifying three tyrosine ligands that were required for growth on Tf or Lf. Computational modeling of the YfeA homologue, AfeA, revealed conserved residues involved in metal binding.

Lactoferrin Alleviates Lipopolysaccharide-Induced Infantile Intestinal Immune Barrier Damage by Regulating an ELAVL1-Related Signaling Pathway

As the most important intestinal mucosal barrier of the main body, the innate immune barrier in intestinal tract plays especially pivotal roles in the overall health conditions of infants and young children; therefore, how to strengthen the innate immune barrier is pivotal. A variety of bioactivities of lactoferrin (LF) has been widely proved, including alleviating enteritis and inhibiting colon cancer; however, the effects of LF on intestinal immune barrier in infants and young children are still unclear, and the specific mechanism on how LF inhibits infantile enteritis by regulating immune signaling pathways is unrevealed. In the present study, we firstly performed pharmacokinetic analyses of LF in mice intestinal tissues, stomach tissues and blood, through different administration methods, to confirm the metabolic method of LF in mammals. Then we constructed in Vitro and in Vivo infantile intestinal immune barrier damage models utilizing lipopolysaccharide (LPS), and evaluated the effects of LF in alleviating LPS-induced intestinal immune barrier damage. Next, the related immune molecular mechanism on how LF exerted protective effects was investigated, through RNA-seq analyses of the mouse primary intestinal epithelial cells, and the specific genes were analyzed and screened out. Finally, the genes and their related immune pathway were validated in mRNA and protein levels; the portions of special immune cells (CD4+ T cells and CD8+ T cells) were also detected to further support our experimental results. Pharmacokinetic analyses demonstrated that the integrity of LF could reach mice stomach and intestine after oral gavage within 12 h, and the proper administration of LF should be the oral route. LF was proven to down-regulate the expression levels of inflammatory cytokines in both the primary intestinal epithelial cells and mice blood, especially LF without iron (Apo-LF), indicating LF alleviated infantile intestinal immune barrier damage induced by LPS. And through RNA-seq analyses of the mouse primary intestinal epithelial cells treated with LPS and LF, embryonic lethal abnormal vision Drosophila 1 (ELAVL1) was selected as one of the key genes, then the ELAVL1/PI3K/NF-κB pathway regulated by LF was verified to participate in the protection of infantile intestinal immune barrier damage in our study. Additionally, the ratio of blood CD4+/CD8+ T cells was significantly higher in the LF-treated mice than in the control mice, indicating that LF distinctly reinforced the overall immunity of infantile mice, further validating the strengthening bioactivity of LF on infantile intestinal immune barrier. In summary, LF was proven to alleviate LPS-induced intestinal immune barrier damage in young mice through regulating ELAVL1-related immune signaling pathways, which would expand current knowledge of the functions of bioactive proteins in foods within different research layers, as well as benefit preclinical and clinical researches in a long run.

MELTF Might Regulate Ferroptosis, Pyroptosis, and Autophagy in Platelet-Rich Plasma-Mediated Endometrial Epithelium Regeneration

The endometrial basal layer is essential for endometrial regeneration, whose disruption leads to thin endometrium or intrauterine adhesion (IUA) with an unsatisfactory prognosis. Emerging data indicate that platelet-rich plasma (PRP) can promote endometrial proliferation, but the mechanism by which PRP regulates endometrial regeneration remains unclear. Herein, we investigated the therapeutic effects and possible mechanisms of PRP on endometrial regeneration. IUA animal model was generated by sham, mechanically damaging endometrium with or without PRP for 10 days. The uterine section in the model group showed degenerative changes with a narrow endometrial lumen, atrophic columnar epithelium, decreased number of endometrial glands, decreased endometrial thickness, and increased collagen deposition. The above disruption could be ameliorated by the PRP. Transcriptome sequencing analysis displayed that the retinol metabolism pathway and extracellular matrix (ECM) receptor interaction pathway were up-regulated and enriched in differential expression genes (DEGs). Melanotransferrin (MELTF) was the key up-regulated gene in PRP-induced endometrial regeneration, which was verified in vivo and in vitro. Ferroptosis, autophagy, and pyroptosis were down-regulated in PRP-treated Ishikawa cells. Conclusively, PRP promotes endometrium regeneration by up-regulating the retinol metabolism and ECM receptor interaction pathway with MELTF. Meanwhile, PRP could also inhibit endometrial epithelial cell death by regulating ferroptosis, autophagy, and pyroptosis.

Lactoferrin: from the structure to the functional orchestration of iron homeostasis

Iron is by far the most widespread and essential transition metal, possessing crucial biological functions for living systems. Despite chemical advantages, iron biology has forced organisms to face with some issues: ferric iron insolubility and ferrous-driven formation of toxic radicals. For these reasons, acquisition and transport of iron constitutes a formidable challenge for cells and organisms, which need to maintain adequate iron concentrations within a narrow range, allowing biological processes without triggering toxic effects. Higher organisms have evolved extracellular carrier proteins to acquire, transport and manage iron. In recent years, a renewed interest in iron biology has highlighted the role of iron-proteins dysregulation in the onset and/or exacerbation of different pathological conditions. However, to date, no resolutive therapy for iron disorders has been found. In this review, we outline the efficacy of Lactoferrin, a member of the transferrin family mainly secreted by exocrine glands and neutrophils, as a new emerging orchestrator of iron metabolism and homeostasis, able to counteract iron disorders associated to different pathologies, including iron deficiency and anemia of inflammation in blood, Parkinson and Alzheimer diseases in the brain and cystic fibrosis in the lung.

Antimicrobial Proteins and Peptides in Avian Eggshell: Structural Diversity and Potential Roles in Biomineralization

The calcitic avian eggshell provides physical protection for the embryo during its development, but also regulates water and gaseous exchange, and is a calcium source for bone mineralization. The calcified eggshell has been extensively investigated in the chicken. It is characterized by an inventory of more than 900 matrix proteins. In addition to proteins involved in shell mineralization and regulation of its microstructure, the shell also contains numerous antimicrobial proteins and peptides (AMPPs) including lectin-like proteins, Bacterial Permeability Increasing/Lipopolysaccharide Binding Protein/PLUNC family proteins, defensins, antiproteases, and chelators, which contribute to the innate immune protection of the egg. In parallel, some of these proteins are thought to be crucial determinants of the eggshell texture and its resulting mechanical properties. During the progressive solubilization of the inner mineralized eggshell during embryonic development (to provide calcium to the embryo), some antimicrobials may be released simultaneously to reinforce egg defense and protect the egg from contamination by external pathogens, through a weakened eggshell. This review provides a comprehensive overview of the diversity of avian eggshell AMPPs, their three-dimensional structures and their mechanism of antimicrobial activity. The published chicken eggshell proteome databases are integrated for a comprehensive inventory of its AMPPs. Their biochemical features, potential dual function as antimicrobials and as regulators of eggshell biomineralization, and their phylogenetic evolution will be described and discussed with regard to their three-dimensional structural characteristics. Finally, the repertoire of chicken eggshell AMPPs are compared to orthologs identified in other avian and non-avian eggshells. This approach sheds light on the similarities and differences exhibited by AMPPs, depending on bird species, and leads to a better understanding of their sequential or dual role in biomineralization and innate immunity.

Functional disruption of transferrin expression alters reproductive physiology in Anopheles culicifacies

BACKGROUND

Iron metabolism is crucial to maintain optimal physiological homeostasis of every organism and any alteration of the iron concentration (i.e. deficit or excess) can have adverse consequences. Transferrins are glycoproteins that play important role in iron transportation and have been widely characterized in vertebrates and insects, but poorly studied in blood-feeding mosquitoes.

RESULTS

We characterized a 2102 bp long transcript AcTrf1a with complete CDS of 1872bp, and 226bp UTR region, encoding putative transferrin homolog protein from mosquito An. culicifacies. A detailed in silico analysis predicts AcTrf1a encodes 624 amino acid (aa) long polypeptide that carries transferrin domain. AcTrf1a also showed a putative N-linked glycosylation site, a characteristic feature of most of the mammalian transferrins and certain non-blood feeding insects. Structure modelling prediction confirms the presence of an iron-binding site at the N-terminal lobe of the transferrin. Our spatial and temporal expression analysis under altered pathophysiological conditions showed that AcTrf1a is abundantly expressed in the fat-body, ovary, and its response is significantly altered (enhanced) after blood meal uptake, and exogenous bacterial challenge. Additionally, non-heme iron supplementation of FeCl3 at 1 mM concentration not only augmented the AcTrf1a transcript expression in fat-body but also enhanced the reproductive fecundity of gravid adult female mosquitoes. RNAi-mediated knockdown of AcTrf1a causes a significant reduction in fecundity, confirming the important role of transferrin in oocyte maturation.

CONCLUSION

All together our results advocate that detailed characterization of newly identified AcTrf1a transcript may help to select it as a unique target to impair the mosquito reproductive outcome.

Comparative Effects between Oral Lactoferrin and Ferrous Sulfate Supplementation on Iron-Deficiency Anemia: A Comprehensive Review and Meta-Analysis of Clinical Trials

Ferrous sulfate is a commonly used iron supplement for the correction of iron-deficiency anemia but with frequent gastrointestinal side effects. Milk-derived iron-binding glycoprotein lactoferrin possesses well gastrointestinal tolerance and fewer side effects caused by the intake of high-dose iron. However, the underlying mechanism of the iron-enhancing effect of lactoferrin remains unclear. In addition, the comparative efficacies between lactoferrin and ferrous sulfate are also remained to be determined. We conducted a systematic review and meta-analysis on published intervention studies to investigate how lactoferrin modulate iron metabolism and evaluate the comparative effects between lactoferrin and ferrous sulfate supplementation on iron absorption, iron storage, erythropoiesis and inflammation. Lactoferrin supplementation had better effects on serum iron (WMD: 41.44 ug/dL; p < 0.00001), ferritin (WMD: 13.60 ng/mL; p = 0.003) and hemoglobin concentration (11.80 g/dL; p < 0.00001), but a reducing effect on fractional iron absorption (WMD: −2.08%; p = 0.02) and IL-6 levels (WMD: −45.59 pg/mL; p < 0.00001) compared with ferrous sulfate. In conclusion, this study supports lactoferrin as a superior supplement to ferrous sulfate regarding the improvement in serum iron parameters and hemoglobin levels. Considering the weak influence of lactoferrin on iron absorption, the anti-inflammation effect of lactoferrin may be the potential mechanism to explain its efficacy on iron status and erythropoiesis.

The Functional Role of Lactoferrin in Intestine Mucosal Immune System and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC) and Crohn's disease (CD), is one of the main types of intestinal inflammatory diseases with intestine mucosal immune disorder. Intestine mucosal immune system plays a remarkable and important role in the etiology and pathogenesis of IBD. Therefore, understanding the intestine mucosal immune mechanism is a key step to develop therapeutic interventions for IBD. Intestine mucosal immune system and IBD are influenced by various factors, such as inflammation, gut permeability, gut microbiota, and nutrients. Among these factors, emerging evidence show that nutrients play a key role in inflammation activation, integrity of intestinal barrier, and immune cell modulation. Lactoferrin (LF), an iron-binding glycoprotein belonging to transferrin family, is a dietary bioactive component abundantly found in mammalian milk. Notably, LF has been reported to perform diverse biological functions including antibacterial activity, anti-inflammatory activity, intestinal barrier protection, and immune cell modulation, and is involved in maintaining intestine mucosal immune homeostasis. The improved understanding of the properties of LF in intestine mucosal immune system and IBD will facilitate its application in nutrition, clinical medicine, and health. Herein, this review outlines the recent advancements on LF as a potential therapeutic intervention for IBD associated with intestine mucosal immune system dysfunction. We hope this review will provide a reference for future studies and lay a theoretical foundation for LF-based therapeutic interventions for IBD by understanding the particular effects of LF on intestine mucosal immune system.

Lactoferrin may inhibit the development of cancer via its immunostimulatory and immunomodulatory activities (Review)

Lactoferrin (Lf) is secreted by ectodermal tissue and has a structure similar to that of transferrin. Although Lf seems to be multifunctional, its main function is related to the natural defense system of mammals. The present review aims to highlight the major actions of Lf, including the regulation of cell growth, the inhibition of toxic compound formation, the removal of harmful free radicals and its important role in immune response regulation. Moreover, Lf has antibacterial, antiviral, antioxidant, anticancer and anti‑inflammatory activities. In addition, the use of Lf for functionalization of drug nanocarriers, with emphasis on tumor‑targeted drug delivery, is illustrated. Such effects serve as an important theoretical basis for its future development and application. In neurodegenerative diseases and the brains of elderly people, Lf expression is markedly upregulated. Lf may exert an anti‑inflammatory effect by inhibiting the formation of hydroxyl free radicals. Through its antioxidant properties, Lf can prevent DNA damage, thereby preventing tumor formation in the central nervous system. In addition, Lf specifically activates the p53 tumor suppressor gene.

Iron and erythropoiesis: A mutual alliance

The large amount of iron required for hemoglobin synthesis keeps iron homeostasis and erythropoiesis inter-connected, both iron levels being affected by increased erythropoiesis, and erythropoiesis regulated by serum iron. The connection between these 2 processes is maintained even when erythropoiesis is ineffective. In the last years great advances in the understanding of the mechanisms of this crosstalk have been achieved thanks to the discovery of 2 essential players: hepcidin, the master regulator of iron homeostasis, and erythroferrone, the long sought erythroid regulator. In addition, how circulating transferrin-bound iron contributes to the crosstalk between the 2 systems has started to be unraveled.

Molecular cloning, characterisation and expression analysis of the vitellogenin genes vtgAo1 and vtgC during ovarian development in Chinese hook snout carp Opsariichthys bidens

Vitellogenesis is essential for oocyte maturation. Vitellogenin (Vtg), a yolk precursor protein, plays an important role in oogenesis and vitellogenesis. Chinese hook snout carp Opsariichthys bidens is an economically important freshwater fish in China whose reproductive and developmental biology are not well understood. In this study, we undertook histological analysis to examine ovary development and oogenesis in O. bidens. The ovaries were divided into Stages II-V and oocytes were divided into perinuclear oocytes, cortical alveoli oocytes, vitellogenic oocytes and mature oocytes. Full-length cDNA sequences were cloned of two vtg genes from the liver of O. bidens, namely Ob-vtgAo1 and Ob-vtgC. Ob-vtgAo1 and Ob-vtgC cDNA are made up of 4136 and 4392 bases respectively and encode proteins containing 1335 and 1250 amino acids respectively. Ob-vtgAo1 contains three yolk protein domains: lipovitellin heavy chain (LvH), phosvitin (Pv) and lipovitellin light chain (LvL), whereas Ob-VtgC contains LvH and LvL, which are incomplete Vtgs. Ob-vtgAo1 and Ob-vtgC mRNA expression was significantly higher in the liver of O. bidens than in all other tissues. In oocytes of Stage II-III ovaries, yolk granules are almost absent and ovarian and hepatic Ob-vtgAo1 and Ob-vtgC expression is low. At Stage IV, the oocyte is filled with yolk granules and ovarian and hepatic Ob-vtgAo1 and Ob-vtgC expression is significantly increased. Collectively, these findings help us better understand vitellogenesis in O. bidens.

Draft Genome of the Sea Cucumber Holothuria glaberrima, a Model for the Study of Regeneration

Regeneration is one of the most fascinating and yet least understood biological processes. Echinoderms, one of the closest related invertebrate groups to humans, can contribute to our understanding of the genetic basis of regenerative processes. Among echinoderms, sea cucumbers have the ability to grow back most of their body parts following injury, including the intestine and nervous tissue. The cellular and molecular events underlying these abilities in sea cucumbers have been most extensively studied in the species Holothuria glaberrima. However, research into the regenerative abilities of this species has been impeded due to the lack of adequate genomic resources. Here, we report the first draft genome assembly of H. glaberrima and demonstrate its value for future genetic studies. Using only short sequencing reads, we assembled the genome into 89,105 scaffolds totaling 1.1 gigabases with an N50 of 25 kilobases. Our BUSCO assessment of the genome resulted in 894 (91.4%) complete and partial genes from 978 genes queried. We incorporated transcriptomic data from several different life history stages to annotate 51,415 genes in our final assembly. To demonstrate the usefulness of the genome, we fully annotated the melanotransferrin (Mtf) gene family, which have a potential role in the regeneration of the sea cucumber intestine. Using these same data, we extracted the mitochondrial genome, which showed high conservation to that of other holothuroids. Thus, these data will be a critical resource for ongoing studies of regeneration and other studies in sea cucumbers.

Lactoferrin: an overview of its main functions, immunomodulatory and antimicrobial role, and clinical significance

Lactoferrin (LF), a glycoprotein found in mucosal secretions, is characterized by a wide range of functions, including immunomodulatory and anti-inflammatory activities. Moreover, several investigations confirmed that LF displays high effectiveness against multiple bacteria and viruses and may be regarded as a potential inhibitor of enveloped viruses, such as presently prevailing SARS-CoV-2. In our review, we discuss available studies about LF functions and bioavailability of different LF forms in in vitro and in vivo models. Moreover, we characterize the potential benefits and side effects of LF use; we also briefly summarize the latest clinical trials examining LF application. Finally, we point potential role of LF in inflammatory bowel disease and indicate its use as a marker for disease severity.

Complex of human Melanotransferrin and SC57.32 Fab fragment reveals novel interdomain arrangement with ferric N-lobe and open C-lobe

Melanotransferrin (MTf) is an iron-binding member of the transferrin superfamily that can be membrane-anchored or secreted in serum. On cells, it can mediate transferrin-independent iron uptake and promote proliferation. In serum, it is a transcytotic iron transporter across the blood-brain barrier. MTf has been exploited as a drug delivery carrier to the brain and as an antibody-drug conjugate (ADC) target due to its oncogenic role in melanoma and its elevated expression in triple-negative breast cancer (TNBC). For treatment of TNBC, an MTf-targeting ADC completed a phase I clinical trial (NCT03316794). The structure of its murine, unconjugated Fab fragment (SC57.32) is revealed here in complex with MTf. The MTf N-lobe is in an active and iron-bound, closed conformation while the C-lobe is in an open conformation incompatible with iron binding. This combination of active and inactive domains displays a novel inter-domain arrangement in which the C2 subdomain angles away from the N-lobe. The C2 subdomain also contains the SC57.32 glyco-epitope, which comprises ten protein residues and two N-acetylglucosamines. Our report reveals novel features of MTf and provides a point of reference for MTf-targeting, structure-guided drug design.

Iron Homeostasis and Metabolism: Two Sides of a Coin

Iron is an ancient, essential and versatile transition metal found in almost all living organisms on Earth. This fundamental trace element is used in the synthesis of heme and iron-sulfur (Fe-S) containing proteins and other vital cofactors that are involved in respiration, redox reactions, catalysis, DNA synthesis and transcription. At the same time, the ability of iron to cycle between its oxidized, ferric (Fe³⁺) and its reduced, ferrous (Fe²⁺) state contributes to the production of free radicals that can damage biomolecules, including proteins, lipids and DNA. In particular, the regulated non-apoptotic cell death ferroptosis is driven by Fe²⁺-dependent lipid peroxidation that can be prevented by iron chelation or genetic inhibition of cellular iron uptake. Therefore, iron homeostasis must be tightly regulated to avoid iron toxicity. This review provides an overview of the origin and chemistry of iron that makes it suitable for a variety of biological functions and addresses how organisms evolved various strategies, including their scavenging and antioxidant machinery, to manage redox-associated drawbacks. Finally, key mechanisms of iron metabolism are highlighted in human diseases and model organisms, underlining the perils of dysfunctional iron handlings.

Treating brain diseases using systemic parenterally-administered protein therapeutics: Dysfunction of the brain barriers and potential strategies

The parenteral administration of protein therapeutics is increasingly gaining importance for the treatment of human diseases. However, the presence of practically impermeable blood-brain barriers greatly restricts access of such pharmaceutics to the brain. Treating brain disorders with proteins thus remains a great challenge, and the slow clinical translation of these therapeutics may be largely ascribed to the lack of appropriate brain delivery system. Exploring new approaches to deliver proteins to the brain by circumventing physiological barriers is thus of great interest. Moreover, parallel advances in the molecular neurosciences are important for better characterizing blood-brain interfaces, particularly under different pathological conditions (e.g., stroke, multiple sclerosis, Parkinson's disease, and Alzheimer's disease). This review presents the current state of knowledge of the structure and the function of the main physiological barriers of the brain, the mechanisms of transport across these interfaces, as well as alterations to these concomitant with brain disorders. Further, the different strategies to promote protein delivery into the brain are presented, including the use of molecular Trojan horses, the formulation of nanosystems conjugated/loaded with proteins, protein-engineering technologies, the conjugation of proteins to polymers, and the modulation of intercellular junctions. Additionally, therapeutic approaches for brain diseases that do not involve targeting to the brain are presented (i.e., sink and scavenging mechanisms).

Exploring Serum Transferrin Regulation of Nonferric Metal Therapeutic Function and Toxicity

Serum transferrin (sTf) plays a pivotal role in regulating iron biodistribution and homeostasis within the body. The molecular details of sTf Fe(III) binding blood transport, and cellular delivery through transferrin receptor-mediated endocytosis are generally well-understood. Emerging interest exists in exploring sTf complexation of nonferric metals as it facilitates the therapeutic potential and toxicity of several of them. This review explores recent X-ray structural and physiologically relevant metal speciation studies to understand how sTf partakes in the bioactivity of key non-redox active hard Lewis acidic metals. It challenges preconceived notions of sTf structure function correlations that were based exclusively on the Fe(III) model by revealing distinct coordination modalities that nonferric metal ions can adopt and different modes of binding to metal-free and Fe(III)-bound sTf that can directly influence how they enter into cells and, ultimately, how they may impact human health. This knowledge informs on biomedical strategies to engineer sTf as a delivery vehicle for metal-based diagnostic and therapeutic agents in the cancer field. It is the intention of this work to open new avenues for characterizing the functionality and medical utility of nonferric-bound sTf and to expand the significance of this protein in the context of bioinorganic chemistry.

Lobe specificity of iron binding to transferrin modulates murine erythropoiesis and iron homeostasis

Transferrin, the major plasma iron-binding molecule, interacts with cell-surface receptors to deliver iron, modulates hepcidin expression, and regulates erythropoiesis. Transferrin binds and releases iron via either or both of 2 homologous lobes (N and C). To test the hypothesis that the specificity of iron occupancy in the N vs C lobe influences transferrin function, we generated mice with mutations to abrogate iron binding in either lobe (TfN-bl or TfC-bl). Mice homozygous for either mutation had hepatocellular iron loading and decreased liver hepcidin expression (relative to iron concentration), although to different magnitudes. Both mouse models demonstrated some aspects of iron-restricted erythropoiesis, including increased zinc protoporphyrin levels, decreased hemoglobin levels, and microcytosis. Moreover, the TfN-bl/N-bl mice demonstrated the anticipated effect of iron restriction on red cell production (ie, no increase in red blood cell [RBC] count despite elevated erythropoietin levels), along with a poor response to exogenous erythropoietin. In contrast, the TfC-bl/C-bl mice had elevated RBC counts and an exaggerated response to exogenous erythropoietin sufficient to ameliorate the anemia. Observations in heterozygous mice further support a role for relative N vs C lobe iron occupancy in transferrin-mediated regulation of iron homeostasis and erythropoiesis.

A peptide derived from melanotransferrin delivers a protein-based interleukin 1 receptor antagonist across the BBB and ameliorates neuropathic pain in a preclinical model

Delivery of biologic drugs across the blood-brain barrier is becoming a reality. However, the solutions often involve the assembly of complex multi-specific antibody molecules. Here we utilize a simple 12 amino-acid peptide originating from the melanotransferrin (MTf) protein that has shown improved brain delivery properties. 3D confocal fluorescence microscopic analysis demonstrated brain parenchymal localisation of a fluorescently labelled antibody (NIP228) when chemically conjugated to either the MTf peptide or full-length MTf protein. Measurement of plasma kinetics demonstrated the MTf peptide fusions had very similar kinetics to an unmodified NIP228 control antibody, whereas the fusion to MTf protein had significantly reduced plasma exposure most likely due to a higher tissue distribution in the periphery. Brain exposure for the MTf peptide fusions was significantly increased for the duration of the study, exceeding that of the fusions to full length MTf protein. Using a neuropathic pain model, we have demonstrated that fusions to interleukin-1 receptor antagonist (IL-1RA) are able to induce significant and durable analgesia following peripheral administration. These data demonstrate that recombinant and chemically conjugated MTf-based brain delivery vectors can deliver therapeutic levels of drug to the central nervous system.

Multiple vitellogenin genes (vtgs) in large yellow croaker (Larimichthys crocea): molecular characterization and expression pattern analysis during ovarian development

The large yellow croaker (Larimichthys crocea) is a marine fish that is economically important to Chinese fisheries, and its reproductive and developmental biology have been extensively investigated. However, the molecular mechanism of oogenesis in L. crocea is not clear. Here, we investigated the multiple vitellogenin (Vtg) system in large yellow croaker. Three different vtg cDNA sequences, including vtgAa, vtgAb and vtgC, were cloned, which indicate the existence of multiple Vtg proteins in large yellow croaker (Lc-Vtgs). Subsequently, the vtg cDNA sequences and predicted Vtg protein structures were analysed, and Vtg protein structures were found to be highly conserved. To research the expression of vtgs during the development of the ovaries, we examined ovarian development and oogenesis by histological analysis. Four stages of ovary development - stages II, III, IV and V - were observed and their boundaries were defined. Soon afterwards, the expression of vtgs in the liver (known as the main site of Vtg synthesis in teleosts) and ovary were analysed. The expression of vtgs was detected in the two tissues. Interestingly, in the early stages of development (stages II and III), there is little or no generation of yolk granules and the expression of vtgs in the liver is low. However, in the late stages (stages IV and V), yolk granules are generated rapidly and the expression of vtgs is significantly increased in the liver. These results support the hypothesis that the Vtgs were synthetized by the liver, and absorbed by the growing oocytes to promote oogenesis in large yellow croaker. We also detected the presence of vtg mRNA in the liver cells and oocytes by in situ hybridization, which indicated that vths were expressed both in the liver and ovaries. Importantly, we found that the distribution of vtgAa and vtgAb mRNA was close to the sites of yolk granule formation in oocytes.

Porcine lactoferrin-derived peptide LFP-20 modulates immune homoeostasis to defend lipopolysaccharide-triggered intestinal inflammation in mice

The performance of immune system is vital for defending the body from pathogens, and it plays a crucial role in health homoeostasis. In a previous study, we have shown that LFP-20, a twenty-amino acid antimicrobial peptide in the N terminus of porcine lactoferrin, modulated inflammatory response in colitis. Here, we further investigated the effects of LFP-20 on immune homoeostasis to elucidate the mechanism of its anti-inflammation action. A lipopolysaccharide (LPS)-triggered systemic inflammatory response mice model was established. On the basis of observed mucosal lesions and apoptosis in small intestine, we found increased macrophage and neutrophil infiltration in ileum after LPS stimulation. Expectedly, LFP-20 pre-treatment attenuated the LPS-mediated immune disorders in ileum. Moreover, the flow cytometry results indicated pre-treatment with LFP-20 sustained the balance of CD3+CD8+ T cells, B cells and natural killer cells in LPS-triggered immune disturbance. Simultaneously, we demonstrated LFP-20 modulated the secretion of both activated Th1-related IL-12p70, interferon-γ, TNF-α and Th2-related IL-4, IL-5 and IL-6. Furthermore, we found LFP-20 facilitated a balanced Th1 and Th2 response, which triggered cellular defence mechanisms and induced B cells to produce opsonising antibodies belonging to certain IgG subclasses to defend against LPS stimulation. Collectively, our study indicated pre-treatment with LFP-20 could defend against LPS-triggered systemic inflammatory response in mice via modulating immune homoeostasis.

Expanding the Orthologous Matrix (OMA) programmatic interfaces: REST API and the OmaDB packages for R and Python

The Orthologous Matrix (OMA) is a well-established resource to identify orthologs among many genomes. Here, we present two recent additions to its programmatic interface, namely a REST API, and user-friendly R and Python packages called OmaDB. These should further facilitate the incorporation of OMA data into computational scripts and pipelines. The REST API can be freely accessed at https://omabrowser.org/api. The R OmaDB package is available as part of Bioconductor at http://bioconductor.org/packages/OmaDB/, and the omadb Python package is available from the Python Package Index (PyPI) at https://pypi.org/project/omadb/.

Nanotoxicity modelling and removal efficiencies of ZnONP

In this paper the aim is to investigate the toxic effect of zinc oxide nanoparticles (ZnONPs) and is to analyze the removal of ZnONP in aqueous medium by the consortium consisted of Daphnia magna and Lemna minor. Three separate test groups are formed: L. minor ([Formula: see text]), D. magna ([Formula: see text]), and L. minor + D. magna ([Formula: see text]) and all these test groups are exposed to three different nanoparticle concentrations ([Formula: see text]). Time-dependent, concentration-dependent, and group-dependent removal efficiencies are statistically compared by non-parametric Mann-Whitney U test and statistically significant differences are observed. The optimum removal values are observed at the highest concentration [Formula: see text] for [Formula: see text], [Formula: see text] for [Formula: see text]and [Formula: see text] for [Formula: see text] and realized at [Formula: see text] for all test groups [Formula: see text]. There is no statistically significant differences in removal at low concentrations [Formula: see text] in terms of groups but [Formula: see text] test groups are more efficient than [Formula: see text] test groups in removal of ZnONP, at [Formula: see text] concentration. Regression analysis is also performed for all prediction models. Different models are tested and it is seen that cubic models show the highest predicted values (R²). In toxicity models, R² values are obtained at (0.892, 0.997) interval. A simple solution-phase method is used to synthesize ZnO nanoparticles. Dynamic Light Scattering and X-Ray Diffraction (XRD) are used to detect the particle size of synthesized ZnO nanoparticles.

Molecular, structural, and functional comparison of N lobe and C lobe of the transferrin from rock bream, Oplegnathus fasciatus, with respect to its immune response

The iron-withholding strategy of innate immunity is an effective antimicrobial defense mechanism that combats microbial infection by depriving microorganisms of Fe³⁺, which is important for their growth and propagation. Transferrins (Tfs) are a group of iron-binding proteins that exert their antimicrobial function through Fe³⁺ sequestration. The current study describes both structural and functional characteristics of a transferrin ortholog from rock bream Oplegnathus fasciatus (RbTf). The RbTf cDNA possesses an open reading frame (ORF) of 2079 bp encoding 693 amino acids. It has a molecular mass of approximately 74 kDa and an isoelectric point of 5.4. In silico analysis revealed that RbTf has two conserved domains: N-terminal domain and C-terminal domain. Pairwise homology analysis and phylogenetic analysis revealed that RbTf shared the highest identity (82.6%) with Dicentrarchus labrax Tf. According to the genomic analysis, RbTf possesses 17 exons and 16 introns, similar to the other orthologs. Here, we cloned the N terminal and C terminal domains of RbTf to evaluate their distinct functional features. Results obtained through the CAS (chrome azurol S) assay confirmed the iron-binding ability of the RbTf, and it was further determined that the iron-binding ability of rRbTfN was higher than that of rRbTfC. The antimicrobial functions of the rRbTfN and the rRbTfC were confirmed via the iron-dependent bacterial growth inhibition assay. Tissue distribution profiling revealed a ubiquitous expression with intense expression in the liver. Temporal assessment revealed that RbTf increased after stimulation of LPS, Edwardsiella tarda, and Streptococcus iniae post injection (p.i.). These findings demonstrated that RbTf is an important antimicrobial protein that can combat bacterial pathogens.

Molecular cloning and expression analysis of Megalobrama amblycephala transferrin gene and effects of exposure to iron and infection with Aeromonas hydrophila

Transferrin (Tf) plays an important function in iron homeostasis and metabolism of organisms. In this study, we identified and characterized the Tf gene in Megalobrama amblycephala and evaluated its expression in basal conditions as well as after iron overload and experimental infection with Aeromonas hydrophila. Furthermore, we studied the iron binding properties of recombinant Tf. The full-length M. amblycephala Tf complementary DNA (cDNA) (GenBank accession no.: KX698308) of 2245 bp was cloned and contained a 1953 bp open reading frame (ORF) encoding 650 amino acid residues and flanked by a 68 bp 5' and a 204 bp 3' untranslated regions (UTR). Predicted conservative structure illustrated that M. amblycephala Tf consisted of two conservative Tf domains. Amino acid sequence alignment revealed that M. amblycephala Tf had high similarity with that of cyprinids deposited in Genbank, and phylogenetic analysis showed that M. amblycephala Tf clustered with Ctenopharyngodon idella and Hypophthalmichthys molitrix. Tissue expression pattern analyses demonstrated that the liver was the main Tf mRNA expressing organ, being significantly higher than other tissues (p < 0.05). In the liver, Tf mRNA expression in fish artificially injected with the pathogenic bacteria A. hydrophila was significantly upregulated, reaching a peak at 12 h post injection (hpi) and then decreasing afterward. The expression in FeCl₃-injected fish showed a similar tendency, but reached a peak at 8 hpi. Meanwhile, fish serum iron significantly decreased following A. hydrophila injection, but increased to peak at 4 hpi and then decreased in FeCl₃-injected fish. The recombinant M. amblycephala Tf showed iron binding capacity using CAS analysis. These results are helpful to understand the structure and regulation of expression of Tf, as well as the specific function of Tf for both immune responses and iron homeostasis.

A molecular docking study of the interactions between human transferrin and seven metallocene dichlorides

Human Transferrin (hTf) is a metal-binding protein found in blood plasma and is well known for its role in iron delivery. With only a 30% of its capacity for Fe⁺³ binding, this protein has the potential ability to transport other metal ions or organometallic compounds from the blood stream to all cell tissues. In this perspective, recent studies have described seven metallocene dichlorides (Cp₂M(IV)Cl₂, M(IV)=V, Mo, W, Nb, Ti, Zr, Hf) suitable as anticancer drugs and less secondary effects than cisplatin. However, these studies have not provided enough data to clearly explain how hTf binds and transports these organometallic compounds into the cells. Thus, a computational docking study with native apo-hTf using Sybyl-X 2.0 program was conducted to explore the binding modes of these seven Cp₂M(IV)Cl₂ after their optimization and minimization using Gaussian 09. Our model showed that the first three Cp₂M(IV)Cl₂ (M(IV)=V, Mo, W) can interact with apo-hTf on a common binding site with the amino acid residues Leu-46, Ile-49, Arg-50, Leu-66, Asp-69, Ala-70, Leu-72, Ala-73, Pro-74 and Asn-75, while the next four Cp₂M(IV)Cl₂ (M(IV)=Nb, Ti, Zr, Hf) showed different binding sites, unknown until now. A decreasing order in the total score (equal to -log Kd) was observed from these docking studies: W (5.4356), Mo (5.2692), Nb (5.1672), V (4.5973), Ti (3.6529), Zr (2.0054) and Hf (1.8811). High and significant correlation between the affinity of these seven ligands (metallocenes) for apo-hTf and their bond angles CpMCp (r=0.94, p<0.01) and Cl-M-Cl (r=0.95, p<0.01) were observed, thus indicating the important role that these bond angles can play in ligand-protein interactions. Fluorescence spectra of apo-hTf, measured at pH 7.4, had a decrease in the fluorescence emission spectrum with increasing concentration of Cp₂M(IV)Cl₂. Experimental data has a good correlation between K_A (r=0.84, p=0.027) and K_d (r=0.94, p=0.0014) values and the calculated total scores obtained from our docking experiments. In conclusion, these results suggest that the seven Cp₂M(IV)Cl₂ used for this study can interact with apo-hTf, and their affinity was directly and inversely proportional to their bond angles CpMCp and ClMCl, respectively. Our docking studies also suggest that the binding of the first three Cp₂M(IV)Cl₂ (M(IV)=V, Mo, W) to hTf could abrogate the formation of the hTf-receptor complex, and as a consequence the metallocene-hTf complex might require another transport mechanism in order to get into the cell.

Melanotransferrin: New Homolog Genes and Their Differential Expression during Intestinal Regeneration in the Sea Cucumber Holothuria glaberrima

Melanotransferrin (MTf) is a protein associated with oncogenetic, developmental, and immune processes which function remains unclear. The MTf gene has been reported in numerous vertebrate and invertebrate species, including echinoderms. We now report the finding of four different MTfs in the transcriptome of the sea cucumber Holothuria glaberrima. Sequence studies and phylogenetic analyses were done to ascertain the similarities among the putative proteins and their relationship with other transferrin family members. The genes were shown to be differentially expressed in various holothurian organs and to respond differently when the animals were challenged with the immune system activator lipopolysaccharide (LPS). Moreover, the four genes were found to be highly overexpressed during the early stages of intestinal regeneration. The finding of four different genes in the holothurian is particularly surprising, because only one MTf gene has been reported in all other animal species sequenced to date. This finding, combined with the increase expression during intestinal regeneration, suggests a new possible function of MTf in organ regenerative processes.

Contributions of transferrin to acute inflammation in the goldfish, C. auratus

Transferrin is an evolutionary conserved protein that in addition to having a critical role in iron transport also has been shown to have a crucial role in host defence, by depriving iron from invading pathogens. Recently cleaved transferrin products was shown to activate macrophages in vitro. We now use an in vivo model of self-resolving peritonitis in goldfish, coupled with gene expression and protein analysis to evaluate the contributions of cleaved transferrin to acute inflammation. We show, for the first time, that cleaved transferrin products are produced in vivo early during an acute inflammatory response. These cleaved transferrin fragments were produced during pathogen-induced, but not sterile, inflammation. Both macrophages and neutrophils were able to contribute to transferrin cleavage. However, only macrophages contributed to this innate process through inducible expression of transferrin. The appearance of transferrin cleavage products in vivo correlated with the influx of leukocytes but did not necessarily correlate the induction of robust respiratory burst and nitric oxide responses. Overall, this study adds to a growing body of work highlighting the role of transferrin as an immune regulator during acute inflammation. Given the significant conservation of this and related molecules, these findings have potentially broad implications for host defences and inflammation control across evolution.

Inhibitory Effects of Synthetic Peptides Containing Bovine Lactoferrin C-lobe Sequence on Bacterial Growth

Lactoferrin is a glycoprotein with various biological effects, with antibacterial activity being one of the first effects reported. This glycoprotein suppresses bacterial growth through bacteriostatic or bactericidal action. It also stimulates the growth of certain kinds of bacteria such as lactic acid bacteria and bifidobacteria. In this study, Asn-Leu-Asn-Arg was selected and chemically synthesized based on the partial sequences of bovine lactoferrin tryptic fragments. Synthetic Asn-Leu-Asn-Arg suppressed the growth of Pseudomonas fluorescens, P. syringae and Escherichia coli. P. fluorescens is a major psychrotrophic bacteria found in raw and pasteurized milk, which decreases milk quality. P. syringae is a harmful infectious bacterium that damages plants. However, synthetic Asn-Leu-Asn-Arg did not inhibit the growth of Lactobacillus acidophilus. It is expected that this synthetic peptide would be the first peptide sequence from the bovine lactoferrin C-lobe that shows antibacterial activity.

A comparative, cross-species investigation of the properties and roles of transferrin- and lactoferrin-binding protein B from pathogenic bacteria

Pathogenic bacteria from the families Neisseriaeceae and Moraxellaceae acquire iron from their host using surface receptors that have the ability to hijack iron from the iron-sequestering host proteins transferrin (Tf) and lactoferrin (Lf). The process of acquiring iron from Tf has been well-characterized, including the role of the surface lipoprotein transferrin-binding protein B (TbpB). In contrast, the only well-defined role for the homologue, LbpB, is in its protection against cationic antimicrobial peptides, which is mediated by regions present in some LbpBs that are highly enriched in glutamic or aspartic acid. In this study we compare the Tf-TbpB and the Lf-LbpB interactions and examine the protective effect of LbpB against extracts from human and transgenic mouse neutrophils to gains insights into the physiological roles of LbpB. The results indicate that in contrast to the Tf-TbpB interaction, Lf-LbpB interaction is sensitive to pH and varies between species. In addition, the results with transgenic mouse neutrophils raise the question of whether there is species specificity in the cleavage of Lf to generate cationic antimicrobial peptides or differences in the potency of peptides derived from mouse and human Lf.

Lactoferrin, a Pleiotropic Protein in Health and Disease

SIGNIFICANCE

Lactoferrin (Lf) is a nonheme iron-binding glycoprotein strongly expressed in human and bovine milk and it plays many functions during infancy such as iron homeostasis and defense against microorganisms. In humans, Lf is mainly expressed in mucosal epithelial and immune cells. Growing evidence suggests multiple physiological roles for Lf after weaning.

RECENT ADVANCES

The aim of this review is to highlight the recent advances concerning multifunctional Lf activities.

CRITICAL ISSUES

First, we will provide an overview of the mechanisms related to Lf intrinsic synthesis or intestinal absorption as well as its interaction with a wide spectrum of mammalian receptors and distribution in organs and cell types. Second, we will discuss the large variety of its physiological functions such as iron homeostasis, transportation, immune regulation, oxidative stress, inflammation, and apoptosis while specifying the mechanisms of action. Third, we will focus on its recent physiopathology implication in metabolic disorders, including obesity, type 2 diabetes, and cardiovascular diseases. Additional efforts are necessary before suggesting the potential use of Lf as a diagnostic marker or as a therapeutic tool.

FUTURE DIRECTIONS

The main sources of Lf in human cardiometabolic disorders should be clarified to identify new perspectives for future research and develop new strategies using Lf in therapeutics. Antioxid. Redox Signal. 24, 813-836.

Transferrin Saturation: A Body Iron Biomarker

Iron is an essential element for several metabolic pathways and physiological processes. The maintenance of iron homeostasis within the human body requires a dynamic and highly sophisticated interplay of several proteins, as states of iron deficiency or excess are both potentially deleterious to health. Among these is plasma transferrin, which is central to iron metabolism not only through iron transport between body tissues in a soluble nontoxic form but also through its protective scavenger role in sequestering free toxic iron. The transferrin saturation (TSAT), an index that takes into account both plasma iron and its main transport protein, is considered an important biochemical marker of body iron status. Its increasing use in many health systems is due to the increased availability of measurement methods, such as calorimetry, turbidimetry, nephelometry, and immunochemistry to estimate its value. However, despite its frequent use in clinical practice to detect states of iron deficiency or iron overload, careful attention should be paid to the inherent limitations of the test especially in certain settings such as inflammation in order to avoid misinterpretation and erroneous conclusions. Beyond its usual clinical use, an emerging body of evidence has linked TSAT levels to major clinical outcomes such as cardiovascular mortality. This has the potential to extend the utility of TSAT index to risk stratification and prognostication. However, most of the current evidence is mainly driven by observational studies where the risk of residual confounding cannot be fully eliminated. Indeed, future efforts are required to fully explore this capability in well-designed clinical trials or prospective large-scale cohorts.

Phylogenomic analysis of transferrin family from animals and plants

Transferrins have been identified in animals and green algae, and they consist of a family of evolutionarily related proteins that play a central role in iron transport, immunity, growth and differentiation. This study assessed the transferrin genes among 100 genomes from a wide range of animal and plant kingdoms. The results showed that putative transferrins were widespread in animals, but their gene quantity and type differ greatly between animal groups. Generally, Mammalia possess abundant transferrin genes, whereas Trematoda contain few ones. Melanotransferrin and serotransferrin are widely distributed in vertebrates, while melanotransferrin-like and transferrin-like 1 are frequent in invertebrates. However, only a few plant species detected putative transferrins, and a novel transferrin member was first uncovered in Angiospermae and Pteridophyta. The structural comparison among transferrin family members revealed seven very well-repeated and conserved characteristic motifs, despite a considerable variation in the overall sequences. The phylogenetic analysis suggested that gene duplication, gene loss and horizontal transfer contributed to the diversification of transferrin family members, and their inferred evolutionary scenario was proposed. These findings help to the understanding of transferrin distribution, characteristic motifs and residues, and evolutionary process.

Molecular insights into a molluscan transferrin homolog identified from disk abalone (Haliotis discus discus) evidencing its detectable role in host antibacterial defense

The basic function of transferrin is to bind iron (III) ions in the medium and to deliver them to the locations where they are required for metabolic processes. It also takes part in the host immune defense mainly via its ability to bind to iron (III) ions. Hence, transferrin is also identified as an important acute-phase protein in host immunity. Abalones are major shellfish aquaculture crops that are susceptible to a range of marine microbial infections. Since transferrin is known to be a major player in innate immunity, in the present study we sought to identify, and molecularly and functionally characterize a transferrin-like gene from disk abalone (Haliotis discus discus) named as AbTrf. AbTrf consisted of a 2187-bp open reading frame (ORF) which encodes a 728 amino acid (aa) protein. The putative amino acid sequence of AbTrf harbored N- and C-terminal transferrin-like domains, active sites for iron binding, and conserved cysteine residues. A constitutive tissue specific AbTrf expression pattern was detected by qPCR in abalones where mantle and muscle showed high AbTrf expression levels. Three immune challenge experiments were conducted using Vibrio parahaemolyticus, Listeria monocytogenes and LPS as stimuli and, subsequently, AbTrf mRNA expression levels were quantified in gill and hemocytes in a time-course manner. The mRNA expression was greatly induced in both tissues in response to both challenges. Evidencing the functional property of transferrins, recombinant AbTrf N-terminal domain (AbTrf-N) showed dose-dependent iron (III) binding activity detected by chrome azurol S (CAS) assay system. Moreover, recombinant AbTrf-N could significantly inhibit the growth of iron-dependent bacterium, Escherichia coli in a dose-dependent manner. However, AbTrf-N was unable to show any detectable bacteriostatic activity against iron-independent bacterium Lactobacillus plantarum (L. plantarum) even at its highest concentration. Collectively, our results suggest that AbTrf might play a significant role in the host innate immunity, possibly by withholding iron from pathogens.

A genome-wide analysis of antimicrobial effector genes and their transcription patterns in Manduca sexta

Antimicrobial proteins/peptides (AMPs) are effectors of innate immune systems against pathogen infection in multicellular organisms. Over half of the AMPs reported so far come from insects, and these effectors act in concert to suppress or kill bacteria, fungi, viruses, and parasites. In this work, we have identified 86 AMP genes in the Manduca sexta genome, most of which seem likely to be functional. They encode 15 cecropins, 6 moricins, 6 defensins, 3 gallerimycins, 4 X-tox splicing variants, 14 diapausins, 15 whey acidic protein homologs, 11 attacins, 1 gloverin, 4 lebocins, 6 lysozyme-related proteins, and 4 transferrins. Some of these genes (e.g. attacins, cecropins) constitute large clusters, likely arising after rounds of gene duplication. We compared the amino acid sequences of M. sexta AMPs with their homologs in other insects to reveal conserved structural features and phylogenetic relationships. Expression data showed that many of them are synthesized in fat body and midgut during the larval-pupal molt. Certain genes contain one or more predicted κB binding sites and other regulatory elements in their promoter regions, which may account for the dramatic mRNA level increases in fat body and hemocytes after an immune challenge. Consistent with these strong mRNA increases, many AMPs become highly abundant in the larval plasma at 24 h after the challenge, as demonstrated in our previous peptidomic study. Taken together, these data suggest the existence of a large repertoire of AMPs in M. sexta, whose expression is up-regulated via immune signaling pathways to fight off invading pathogens in a coordinated manner.

Transferrin: Endocytosis and Cell Signaling in Parasitic Protozoa

Iron is the fourth most abundant element on Earth and the most abundant metal in the human body. This element is crucial for life because almost all organisms need iron for several biological activities. This is the case with pathogenic organisms, which are at the vanguard in the battle with the human host for iron. The latest regulates Fe concentration through several iron-containing proteins, such as transferrin. The transferrin receptor transports iron to each cell that needs it and maintains it away from pathogens. Parasites have developed several strategies to obtain iron as the expression of specific transferrin receptors localized on plasma membrane, internalized through endocytosis. Signal transduction pathways related to the activation of the receptor have functional importance in proliferation. The study of transferrin receptors and other proteins with action in the signaling networks is important because these proteins could be used as therapeutic targets due to their specificity or to differences with the human counterpart. In this work, we describe proteins that participate in signal transduction processes, especially those that involve transferrin endocytosis, and we compare these processes with those found in T. brucei, T. cruzi, Leishmania spp., and E. histolytica parasites.