Structure of the human transferrin receptor-transferrin complex

Confinement energy landscape classification reveals membrane receptor nano-organization mechanisms

The cell membrane organization has an essential functional role through the control of membrane receptor confinement in micro- or nanodomains. Several mechanisms have been proposed to account for these properties, although some features have remained controversial, notably the nature, size, and stability of cholesterol- and sphingolipid-rich domains or lipid rafts. Here, we probed the effective energy landscape acting on single-nanoparticle-labeled membrane receptors confined in raft nanodomains- epidermal growth factor receptor (EGFR), Clostridium perfringens ε-toxin receptor (CPεTR), and Clostridium septicum α-toxin receptor (CSαTR)-and compared it with hop-diffusing transferrin receptors. By establishing a new analysis pipeline combining Bayesian inference, decision trees, and clustering approaches, we systematically classified single-protein trajectories according to the type of effective confining energy landscape. This revealed the existence of only two distinct organization modalities: confinement in a quadratic energy landscape for EGFR, CPεTR, and CSαTR (A), and free diffusion in confinement domains resulting from the steric hindrance due to F-actin barriers for transferrin receptor (B). The further characterization of effective confinement energy landscapes by Bayesian inference revealed the role of interactions with the domain environment in cholesterol- and sphingolipid-rich domains with (EGFR) or without (CPεTR and CSαTR) interactions with F-actin to regulate the confinement energy depth. These two distinct mechanisms result in the same organization type (A). We revealed that the apparent domain sizes for these receptor trajectories resulted from Brownian exploration of the energy landscape in a steady-state-like regime at a common effective temperature, independently of the underlying molecular mechanisms. These results highlight that confinement domains may be adequately described as interaction hotspots rather than rafts with abrupt domain boundaries. Altogether, these results support a new model for functional receptor confinement in membrane nanodomains and pave the way to the constitution of an atlas of membrane protein organization.

A detailed overview of quercetin: implications for cell death and liver fibrosis mechanisms

Background

Quercetin, a widespread polyphenolic flavonoid, is known for its extensive health benefits and is commonly found in the plant kingdom. The natural occurrence and extraction methods of quercetin are crucial due to its bioactive potential.

Purpose

This review aims to comprehensively cover the natural sources of quercetin, its extraction methods, bioavailability, pharmacokinetics, and its role in various cell death pathways and liver fibrosis.

Methods

A comprehensive literature search was performed across several electronic databases, including PubMed, Embase, CNKI, Wanfang database, and ClinicalTrials.gov, up to 10 February 2024. The search terms employed were "quercetin", "natural sources of quercetin", "quercetin extraction methods", "bioavailability of quercetin", "pharmacokinetics of quercetin", "cell death pathways", "apoptosis", "autophagy", "pyroptosis", "necroptosis", "ferroptosis", "cuproptosis", "liver fibrosis", and "hepatic stellate cells". These keywords were interconnected using AND/OR as necessary. The search focused on studies that detailed the bioavailability and pharmacokinetics of quercetin, its role in different cell death pathways, and its effects on liver fibrosis.

Results

This review details quercetin's involvement in various cell death pathways, including apoptosis, autophagy, pyroptosis, necroptosis, ferroptosis, and cuproptosis, with particular attention to its regulatory influence on apoptosis and autophagy. It dissects the mechanisms through which quercetin affects these pathways across different cell types and dosages. Moreover, the paper delves into quercetin's effects on liver fibrosis, its interactions with hepatic stellate cells, and its modulation of pertinent signaling cascades. Additionally, it articulates from a physical organic chemistry standpoint the uniqueness of quercetin's structure and its potential for specific actions in the liver.

Conclusion

The paper provides a detailed analysis of quercetin, suggesting its significant role in modulating cell death mechanisms and mitigating liver fibrosis, underscoring its therapeutic potential.

Ferroptosis in renal fibrosis: a mini-review

Ferroptosis is a novel form of programmed cell death that is iron-dependent and distinct from autophagy, apoptosis, and necroptosis. It is primarily characterised by a decrease in glutathione peroxidase 4 (GPX4) activity, or by the accumulation of lipid peroxidation and reactive oxygen species (ROS). Renal fibrosis is a common pathological change in the progression of various primary and secondary renal diseases to end-stage renal disease and poses a serious threat to human health with high morbidity and mortality. Multiple pathways contribute to the development of renal fibrosis, with ferroptosis playing a crucial role in renal fibrosis pathogenesis due to its involvement in the production of ROS. Ferroptosis is related to several signalling pathways, including System Xc-/GPX4, abnormal iron metabolism and lipid peroxidation. A number of studies have indicated that ferroptosis is closely involved in the process of renal fibrosis caused by various kidney diseases such as glomerulonephritis, renal ischaemia-reperfusion injury, diabetic nephropathy and renal calculus. Identifying the underlying molecular mechanisms that determine cell death would open up new insights to address a therapeutic strategy to renal fibrosis. The review aimed to browse and summarise the known mechanisms of ferroptosis that may be associated with biological reactions of renal fibrosis.

Emodin induces ferroptosis in colorectal cancer through NCOA4-mediated ferritinophagy and NF-κb pathway inactivation

Ferroptosis is a new programmed cell death characterized by iron-dependent lipid peroxidation. Targeting ferroptosis is considered a promising strategy for anti-cancer therapy. Recently, natural compound has gained increased attention for their advantage in cancer treatment, and the exploration of natural compounds as ferroptosis inducers offers a hopeful avenue for advancing cancer treatment modalities. Emodin is a natural anthraquinone derivative in many widely used Chinese medicinal herbs. In our previous study, we predicted that the anti-cancer effect of Emodin might related to ferroptosis by using RNA-seq in colorectal cancer (CRC). Thus, in this study, we aim to investigate the molecular mechanism underlying Emodin-mediated ferroptosis in CRC. Cell-based assays including CCK-8, colony formation, EdU, and Annexin V/PI staining were employed to assess Emodin's impact on cell proliferation and apoptosis. Furthermore, various techniques such as FerroOrange staining, C11-BODIPY 581/591 staining, iron, MDA, GSH detection assay and transmission electron microscopy were performed to examine the role of Emodin in ferroptosis. Additionally, specific NCOA4 knockdown cell lines were generated to elucidate the involvement of NCOA4 in Emodin-induced ferroptosis. Moreover, the effects of Emodin on ferroptosis were further confirmed through the application of inhibitors, including Ferrostatin-1, 3-MA, DFO, and PMA. As a results, Emodin inhibited proliferation and induced apoptosis in CRC cells. Emodin could decrease GSH content, xCT and GPX4 expression, meanwhile increasing ROS generation, MDA, and lipid peroxidation, and these effects could reverse by ferroptosis inhibitor, Ferostatin-1, iron chelator DFO, autophagy inhibitor 3-MA and NCOA4 silencing. Moreover, Emodin could inactivate NF-κb pathway, and PMA, an activator of NF-κb pathway could alleviate Emodin-induced ferroptosis in CRC cells. Xenograft mouse model also showed that Emodin suppressed tumor growth and induced ferroptosis in vivo. In conclusion, these results suggested that Emodin induced ferroptosis through NCOA4-mediated ferritinophagy by inactivating NF-κb pathway in CRC cells. These findings not only identified a novel role for Emodin in ferroptosis but also indicated that Emodin may be a valuable candidate for the development of an anti-cancer agent.

Artesunate-loaded solid lipid nanoparticles resist esophageal squamous cell carcinoma by inducing Ferroptosis through inhibiting the AKT/mTOR signaling

Esophageal squamous cell carcinoma (ESCC) is a severe malignancy with high incidence and mortality rate in China, while the application of standard chemotherapeutic drugs for ESCC meets the barriers of high toxicity and multiple drug resistance (MDR). In recent years, the anticancer effects of artesunate (ART), a Chinese medicine monomer have gained extensive attentions due to its characteristics of low toxicity, high potency, and reversal of MDR. In this study, we develop the artesunate-loaded solid lipid nanoparticles (SLNART) to overcome the poor water solubility and bioavailability of ART, further improving the efficiency of ART on ESCC treatment. Especially mentioned, SLNART is shown to present marked inhibitory effects on ESCC development based on the induction of ferroptosis by two pathways included upregulating TFR to increase Fe2+ ions and inhibiting the AKT/mTOR signaling to downregulate GPX4. Collectively, this study is the first to pave a promising approach for ESCC therapy based on a strategy of developing SLNART to induce ferroptosis by mediating Fe2+ ions and AKT/mTOR signaling.

Research advances on molecular mechanism and natural product therapy of iron metabolism in heart failure

The progression of heart failure (HF) is complex and involves multiple regulatory pathways. Iron ions play a crucial supportive role as a cofactor for important proteins such as hemoglobin, myoglobin, oxidative respiratory chain, and DNA synthetase, in the myocardial energy metabolism process. In recent years, numerous studies have shown that HF is associated with iron dysmetabolism, and deficiencies in iron and overload of iron can both lead to the development of various myocarditis diseases, which ultimately progress to HF. Iron toxicity and iron metabolism may be key targets for the diagnosis, treatment, and prevention of HF. Some iron chelators (such as desferrioxamine), antioxidants (such as ascorbate), Fer-1, and molecules that regulate iron levels (such as lactoferrin) have been shown to be effective in treating HF and protecting the myocardium in multiple studies. Additionally, certain natural compounds can play a significant role by mediating the imbalance of iron-related signaling pathways and expression levels. Therefore, this review not only summarizes the basic processes of iron metabolism in the body and the mechanisms by which they play a role in HF, with the aim of providing new clues and considerations for the treatment of HF, but also summarizes recent studies on natural chemical components that involve ferroptosis and its role in HF pathology, as well as the mechanisms by which naturally occurring products regulate ferroptosis in HF, with the aim of providing reference information for the development of new ferroptosis inhibitors and lead compounds for the treatment of HF in the future.

Inhibition of ferroptosis: A new direction in the treatment of ulcerative colitis by traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) is a chronic idiopathic intestinal disease of unknown cause and has been classified as one of the modern intractable diseases by the World Health Organization (WHO). Ferroptosis, as an iron-ion-dependent mode of programmed cell death, is closely related to iron metabolism, lipid peroxidation, and imbalance of the antioxidant system, and plays an important role in the development of UC. In this paper, we will review the regulatory pathways of ferroptosis, the relationship between ferroptosis and the pathogenesis of UC, and the treatment of UC by TCM from the perspective of ferroptosis inhibition, and summarize the mechanism of action of the active ingredients of TCM and TCM compounds to improve UC through ferroptosis inhibition, and look forward to the prospect of the application of ferroptosis inhibition by TCM in the treatment of UC.

AIM OF THIS REVIEW

This paper aims to elucidate the mechanism of action of TCM active ingredients and TCM combinations in the treatment of UC by inhibiting ferroptosis. The active ingredients of TCM have the significant advantages of multi-targets and multi-pathways, and ferroptosis is the current research hotspot in the prevention and treatment of UC, so the inhibition of ferroptosis by TCM is a key direction for future research.

MATERIALS AND METHODS

The keywords "ferroptosis", "ulcerative colitis" and "TCM" were searched in Pubmed, CNKI, and Wed of Science databases. Papers related to clinical trials and pharmacological research up to August 2023 were screened for inclusion. Combined with the theory of TCM, we systematically summarized the effects of TCM active ingredients and TCM combinations in inhibiting ferroptosis and thus preventing UC.

RESULTS

A large number of studies have shown that TCM active ingredients and TCM combinations inhibit the inflammatory response and oxidative stress in the course of UC mainly by interfering with iron metabolism, correcting lipid metabolism and peroxidative accumulation, and regulating the processes of glutathione (GSH) and glutathione peroxidase 4 (GPX4), to improve colonic mucosal damage and promote the repair of colonic mucosal tissue.

CONCLUSION

Since the study of ferroptosis in UC is still in the exploratory stage, many issues still deserve attention in the future. This paper reviews the mechanism of ferroptosis inhibition by TCM active ingredients and TCM combinations to prevent and treat UC. In the future, we should also further increase the number of clinical experimental studies to explore whether more TCM medicines can play a therapeutic role in UC by inhibiting ferroptosis, and explore more pathways and genes targeting the inhibition of ferroptosis, to seek more TCM therapies for UC. We believe that the use of TCM active ingredients and TCM combinations to regulate ferroptosis is an important direction for future UC prevention and treatment.

Advancements of the Molecular Directed Design and Structure-Activity Relationship of Ferritin Nanocage

Ferritin nanocages possess remarkable structural properties and biological functions, making them highly attractive for applications in functional materials and biomedicine. This comprehensive review presents an overview of the molecular characteristics, extraction and identification of ferritin, ferritin receptors, as well as the advancements in the directional design of high-order assemblies of ferritin and the applications based on its unique structural properties. Specifically, this Review focuses on the regulation of ferritin assembly from one to three dimensions, leveraging the symmetry of ferritin and modifications on key interfaces. Furthermore, it discusses targeted delivery of nutrition and drugs through facile loading and functional modification of ferritin. The aim of this Review is to inspire the design of micro/nano functional materials using ferritin and the development of nanodelivery vehicles for nutritional fortification and disease treatment.

The crosstalk between exosomes and ferroptosis: a review

Exosomes are a subtype of extracellular vesicles composed of bioactive molecules, including nucleic acids, proteins, and lipids. Exosomes are generated by the fusion of intracellular multivesicular bodies (MVBs) with the cell membrane and subsequently released into the extracellular space to participate in intercellular communication and diverse biological processes within target cells. As a crucial mediator, exosomes have been implicated in regulating ferroptosis-an iron-dependent programmed cell death characterized by lipid peroxide accumulation induced by reactive oxygen species. The involvement of exosomes in iron, lipid, and amino acid metabolism contributes to their regulatory role in specific mechanisms underlying how exosomes modulate ferroptosis, which remains incompletely understood, and some related studies are still preliminary. Therefore, targeting the regulation of ferroptosis by exosomes holds promise for future clinical treatment strategies across various diseases. This review aims to provide insights into the pathophysiology and mechanisms governing the interaction between exosomes and ferroptosis and their implications in disease development and treatment to serve as a reference for further research.

Comparing in vitro affinity measurements of antibodies to TfR1: Surface plasmon resonance versus on-cell affinity

Despite years of utilizing the transferrin receptor 1 (TfR1) to transport large biomolecules into the brain, there is no consensus on how to optimally measure affinity to it. The aim of this study was to compare different methods for measuring the affinities of anti-TfR1 antibodies. Antibodies 15G11, OX26 and 8D3 are known to successfully carry large biologics across the blood-brain barrier in humans, rats, and mice, respectively. The affinity to their respective species of TfR1 was measured with different surface plasmon resonance setups in Biacore and an on-cell assay. When the antibody was captured and TfR1 was the analyte, the dissociation in Biacore was very slow. The dissociation was faster when the antibody was the analyte and TfR1 was the ligand. The Biacore setup with capture of N-terminal FLAG-tag TfR1 yielded the most similar apparent affinities as the cell assay. In conclusion, it is important to evaluate assay parameters including assay orientation, surface capture method, and antibody-format when comparing binding kinetics for TfR1 antibodies. Although it seems possible to determine relative affinities of TfR1 antibodies using the methods described here, both the FLAG-tag TfR1 capture setup and cell assays likely yield apparent affinities that are most translatable in vivo.

Tumor iron homeostasis and immune regulation

Abnormal iron metabolism has long been regarded as a key metabolic hallmark of cancer. As a critical cofactor, iron contributes to tumor progression by participating in various processes such as mitochondrial electron transport, gene regulation, and DNA synthesis or repair. Although the role of iron in tumor cells has been widely studied, recent studies have uncovered the interplay of iron metabolism between tumor cells and immune cells, which may affect both innate and adaptive immune responses. In this review, we discuss the current understanding of the regulatory networks of iron metabolism between cancer cells and immune cells and how they contribute to antitumor immunity, and we analyze potential therapeutics targeting iron metabolism. Also, we highlight several key challenges and describe potential therapeutic approaches for future investigations.

Mechanisms controlling cellular and systemic iron homeostasis

In mammals, hundreds of proteins use iron in a multitude of cellular functions, including vital processes such as mitochondrial respiration, gene regulation and DNA synthesis or repair. Highly orchestrated regulatory systems control cellular and systemic iron fluxes ensuring sufficient iron delivery to target proteins is maintained, while limiting its potentially deleterious effects in iron-mediated oxidative cell damage and ferroptosis. In this Review, we discuss how cells acquire, traffick and export iron and how stored iron is mobilized for iron-sulfur cluster and haem biogenesis. Furthermore, we describe how these cellular processes are fine-tuned by the combination of various sensory and regulatory systems, such as the iron-regulatory protein (IRP)-iron-responsive element (IRE) network, the nuclear receptor co-activator 4 (NCOA4)-mediated ferritinophagy pathway, the prolyl hydroxylase domain (PHD)-hypoxia-inducible factor (HIF) axis or the nuclear factor erythroid 2-related factor 2 (NRF2) regulatory hub. We further describe how these pathways interact with systemic iron homeostasis control through the hepcidin-ferroportin axis to ensure appropriate iron fluxes. This knowledge is key for the identification of novel therapeutic opportunities to prevent diseases of cellular and/or systemic iron mismanagement.

Ferritinophagy induced ferroptosis in the management of cancer

BACKGROUND

Ferroptosis, a newly form of regulated cell death (RCD), is characterized by iron dyshomeostasis and unrestricted lipid peroxidation. Emerging evidence depicts a pivotal role for ferroptosis in driving some pathological processes, especially in cancer. Triggering ferroptosis can suppress tumor growth and induce an anti-tumor immune response, denoting the therapeutic promises for targeting ferroptosis in the management of cancer. As an autophagic phenomenon, ferritinophagy is critical to induce ferroptosis by degradation of ferritin to release intracellular free iron. Recently, a great deal of effort has gone into designing and developing anti-cancer strategies based on targeting ferritinophagy to induce ferroptosis.

CONCLUSION

This review delineates the regulatory mechanism of ferritinophagy firstly and summarizes the role of ferritinophagy-induced ferroptosis in cancer. Moreover, the strategies targeting ferritinophagy to induce ferroptosis are highlighted to unveil the therapeutic value of ferritinophagy as a target to manage cancer. Finally, the future research directions on how to cope with the challenges in developing ferritinophagy promoters into clinical therapeutics are discussed.

β-Lapachone induces ferroptosis of colorectal cancer cells via NCOA4-mediated ferritinophagy by activating JNK pathway

β-Lapachone is a natural product that can promote ROS generation and ultimately triggers tumor cells death by inducing DNA damage. Recent studies have indicated that the targeting of ferroptosis or iron metabolism is a feasible strategy for treating cancer. In this study, bulk RNA-seq analysis suggested that β-Lapachone might induce ferroptosis in CRC cells. We further tested this hypothesis using a xenograft model of human colorectal cancer as an animal model and in SW620 and DLD-1 of CRC cell lines. Western blot was used to determine the key proteins of ferroptosis (SLC7A11, GPX4), autophagy (LC3B, P62, ATG7), ferritinophagy (NCOA4, FTH1, TFRC), and JNK pathway (p-JNK, JNK, p-c-Jun, c-Jun). The levels of MDA, GSH/GSSG, lipid ROS, and intracellular ferrous iron were determined after β-Lapachone treatment, and inhibitors of various pathways, including NAC, Ferrostatin-1, DFO, 3-MA, and SP600125 were utilized to explore the molecular mechanism underlying β-Lapachone-mediated ferroptosis. As the result, we identified that β-Lapachone inhibited cell proliferation and induced apoptosis, autophagy, and ROS generation. In addition, β-Lapachone induced ferroptosis as demonstrated by intra-cellular iron overload, increased levels of lipid ROS and MDA. Mechanistically, JNK signaling pathway was involved in β-Lapachone-induced xCT/GPX4-mediated ferroptosis and NCOA4-mediated ferritinophagy in CRC cells. In vivo experiments in nude mice demonstrated that β-Lapachone significantly inhibited CRC growth and induced ferroptosis and NCOA4-mediated ferritinophagy. These findings not only identify a novel role for β-Lapachone in ferroptosis but also indicate that β-Lapachone may be a valuable candidate for the research and development of anti-cancer therapeutic agents.

HECW1 induces NCOA4-regulated ferroptosis in glioma through the ubiquitination and degradation of ZNF350

Tumor suppression by inducing NCOA4-mediated ferroptosis has been shown to be feasible in a variety of tumors, including gliomas. However, the regulatory mechanism of ferroptosis induced by NCOA4 in glioma has not been studied deeply. HECW1 and ZNF350 are involved in the biological processes of many tumors, but their specific effects and mechanisms on glioma are still unclear. In this study, we found that HECW1 decreased the survival rate of glioma cells and enhanced iron accumulation, lipid peroxidation, whereas ZNF350 showed the opposite effect. Mechanistically, HECW1 directly regulated the ubiquitination and degradation of ZNF350, eliminated the transcriptional inhibition of NCOA4 by ZNF350, and ultimately activated NCOA4-mediated iron accumulation, lipid peroxidation, and ferroptosis. We demonstrate that HECW1 induces ferroptosis and highlight the value of HECW1 and ZNF350 in the prognostic evaluation of patients with glioma. We also elucidate the mechanisms underlying the HECW1/ZNF350/NCOA4 axis and its regulation of ferroptosis. Our findings enrich the understanding of ferroptosis and provide potential treatment options for glioma patients.

Iron and copper: critical executioners of ferroptosis, cuproptosis and other forms of cell death

Regulated cell death (RCD) is a regulable cell death that involves well-organized signaling cascades and molecular mechanisms. RCD is implicated in fundamental processes such as organ production and tissue remodeling, removing superfluous structures or cells, and regulating cell numbers. Previous studies have not been able to reveal the complete mechanisms, and novel methods of RCD are constantly being proposed. Two metal ions, iron (Fe) and copper (Cu) are essential factors leading to RCDs that not only induce ferroptosis and cuproptosis, respectively but also lead to cell impairment and eventually diverse cell death. This review summarizes the direct and indirect mechanisms by which Fe and Cu impede cell growth and the various forms of RCD mediated by these two metals. Moreover, we aimed to delineate the interrelationships between these RCDs with the distinct pathways of ferroptosis and cuproptosis, shedding light on the complex and intricate mechanisms that govern cellular survival and death. Finally, the prospects outlined in this review suggest a novel approach for investigating cell death, which may involve integrating current therapeutic strategies and offer a promising solution to overcome drug resistance in certain diseases. Video Abstract.

Non-apoptotic programmed cell deaths in diabetic pulmonary dysfunction: the new side of advanced glycation end products

Diabetes mellitus (DM) is a chronic metabolic disorder that affects multiple organs and systems, including the pulmonary system. Pulmonary dysfunction in DM patients has been observed and studied for years, but the underlying mechanisms have not been fully understood. In addition to traditional mechanisms such as the production and accumulation of advanced glycation end products (AGEs), angiopathy, tissue glycation, oxidative stress, and systemic inflammation, recent studies have focused on programmed cell deaths (PCDs), especially the non-apoptotic ones, in diabetic pulmonary dysfunction. Non-apoptotic PCDs (NAPCDs) including autophagic cell death, necroptosis, pyroptosis, ferroptosis, and copper-induced cell death have been found to have certain correlations with diabetes and relevant complications. The AGE-AGE receptor (RAGE) axis not only plays an important role in the traditional pathogenesis of diabetes lung disease but also plays an important role in non-apoptotic cell death. In this review, we summarize novel studies about the roles of non-apoptotic PCDs in diabetic pulmonary dysfunction and focus on their interactions with the AGE-RAGE axis.

Affinity Maturated Transferrin Receptor Apical Domain Blocks Machupo Virus Glycoprotein Binding

Transferrin receptor 1 (TfR) delivers iron across cellular membranes by shuttling the ion carrier protein transferrin. This ability to deliver large protein ligands inside cells is taken advantage of by pathogens to infiltrate human cells. Notably, the receptor's outermost ectodomain, the apical domain, is used as a point of attachment for several viruses including hemorrhagic arenaviruses. To better understand interactions with the receptor it would be advantageous to probe sequence determinants in the apical domain with viral spike proteins. Here, we carried out affinity maturation of our computationally designed apical domain from human TfR to identify underlying driving forces that lead to better binding. The improved variants were confirmed by in vitro surface plasmon resonance measurements with dissociation constants obtained in the lower nanomolar range. It was found that the strong binding affinities for the optimized variants matched the strength of interactions with the native receptor. The structure of the best variant was determined experimentally indicating that the conformational change in the hairpin binding motif at the protein-protein interface plays a crucial role. The experimental methodology can be straightforwardly applied to other arenavirus or pathogens that use the apical domain. It can further be useful to probe host-virus compatibility or therapeutic strategies based on the transferrin receptor decoys.

Interaction Between the Transferrin Protein and Plutonium (and Thorium), What's New?

Transferrin (Tf) is a glycoprotein that transports iron from the serum to the various organs. Several studies have highlighted that Tf can interact with metals other than Fe(III), including actinides that are chemical and radiological toxics. We propose here to report on the behavior of Th(IV) and Pu(IV) in comparison with Fe(III) upon Tf complexation. We considered UV-Vis and IR data of the M2 Tf complex (M=Fe, Th, Pu) and combined experimental EXAFS data with MD models. EXAFS data of the first M-O coordination sphere are consistent with the MD model considering 1 synergistic carbonate. Further EXAFS data analysis strongly suggests that contamination by Th/Pu colloids seems to occur upon Tf complexation, but it seems limited. SAXS data have also been recorded for all complexes and also after the addition of Deferoxamine-B (DFOB) in the medium. The Rg values are very close for apoTf, ThTf and PuTf, but slightly larger than for holoTf. Data suggest that the structure of the protein is more ellipsoidal than spherical, with a flattened oblate form. From this data, the following order of conformation size might be considered:holoTf Collapse

Key Words

• Plutonium
• SAX
• Transferrin
• XAS
• metalloprotein

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MESH Headings

• Transferrin/chemistry
• Plutonium/chemistry
• Thorium/chemistry
• Ferric Compounds
• Scattering, Small Angle
• X-Ray Diffraction

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Grants

• Ministère de l'Enseignement supérieur, de la Recherche et de l'Innovation

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Affiliation(s)

Cyril Zurita Université Côte d'Azur, CNRS, Institut de Chimie de Nice, 06108, Nice, France
Satoru Tsushima Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01328, Dresden, Germany Internationnal Research Frontiers Initiative, Institute of Innovative Research, Tokyo Institute of Technology, Meguro, 152-8550, Tokyo, Japan
Pier Lorenzo Solari Synchrotron SOLEIL, L'Orme des Merisiers, 91190, Saint Aubin, France
Denis Menut Synchrotron SOLEIL, L'Orme des Merisiers, 91190, Saint Aubin, France
Sandrine Dourdain ICSM, Université de Montpellier, CEA, CNRS, ENSCM, Marcoule, France
Aurélie Jeanson Université Côte d'Azur, CNRS, Institut de Chimie de Nice, 06108, Nice, France
Gaëlle Creff Université Côte d'Azur, CNRS, Institut de Chimie de Nice, 06108, Nice, France
Christophe Den Auwer Université Côte d'Azur, CNRS, Institut de Chimie de Nice, 06108, Nice, France

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Designed Endocytosis-Triggering Proteins mediate Targeted Degradation

Endocytosis and lysosomal trafficking of cell surface receptors can be triggered by interaction with endogenous ligands. Therapeutic approaches such as LYTAC1,2 and KineTAC3, have taken advantage of this to target specific proteins for degradation by fusing modified native ligands to target binding proteins. While powerful, these approaches can be limited by possible competition with the endogenous ligand(s), the requirement in some cases for chemical modification that limits genetic encodability and can complicate manufacturing, and more generally, there may not be natural ligands which stimulate endocytosis through a given receptor. Here we describe general protein design approaches for designing endocytosis triggering binding proteins (EndoTags) that overcome these challenges. We present EndoTags for the IGF-2R, ASGPR, Sortillin, and Transferrin receptors, and show that fusing these tags to proteins which bind to soluble or transmembrane protein leads to lysosomal trafficking and target degradation; as these receptors have different tissue distributions, the different EndoTags could enable targeting of degradation to different tissues. The modularity and genetic encodability of EndoTags enables AND gate control for higher specificity targeted degradation, and the localized secretion of degraders from engineered cells. The tunability and modularity of our genetically encodable EndoTags should contribute to deciphering the relationship between receptor engagement and cellular trafficking, and they have considerable therapeutic potential as targeted degradation inducers, signaling activators for endocytosis-dependent pathways, and cellular uptake inducers for targeted antibody drug and RNA conjugates.

Transferrin-Targeted Liposomes in Glioblastoma Therapy: A Review

Glioblastoma (GBM) is a highly aggressive brain tumor, and its treatment is further complicated by the high selectivity of the blood-brain barrier (BBB). The scientific community is urgently seeking innovative and effective therapeutic solutions. Liposomes are a promising new tool that has shown potential in addressing the limitations of chemotherapy, such as poor bioavailability and toxicity to healthy cells. However, passive targeting strategies based solely on the physicochemical properties of liposomes have proven ineffective due to a lack of tissue specificity. Accordingly, the upregulation of transferrin receptors (TfRs) in brain tissue has led to the development of TfR-targeted anticancer therapeutics. Currently, one of the most widely adopted methods for improving drug delivery in the treatment of GBM and other neurological disorders is the utilization of active targeting strategies that specifically target this receptor. In this review, we discuss the role of Tf-conjugated liposomes in GBM therapy and present some recent studies investigating the drug delivery efficiency of Tf-liposomes; in addition, we address some challenges currently facing this approach to treatment and present some potential improvement possibilities.

Enhanced in vivo blood brain barrier transcytosis of macromolecular cargo using an engineered pH-sensitive mouse transferrin receptor binding nanobody

BACKGROUND

The blood brain barrier limits entry of macromolecular diagnostic and therapeutic cargos. Blood brain barrier transcytosis via receptor mediated transport systems, such as the transferrin receptor, can be used to carry macromolecular cargos with variable efficiency. Transcytosis involves trafficking through acidified intracellular vesicles, but it is not known whether pH-dependent unbinding of transport shuttles can be used to improve blood brain barrier transport efficiency.

METHODS

A mouse transferrin receptor binding nanobody, NIH-mTfR-M1, was engineered to confer greater unbinding at pH 5.5 vs 7.4 by introducing multiple histidine mutations. The histidine mutant nanobodies were coupled to neurotensin for in vivo functional blood brain barrier transcytosis testing via central neurotensin-mediated hypothermia in wild-type mice. Multi-nanobody constructs including the mutant M1R56H, P96H, Y102H and two copies of the P2X7 receptor-binding 13A7 nanobody were produced to test proof-of-concept macromolecular cargo transport in vivo using quantitatively verified capillary depleted brain lysates and in situ histology.

RESULTS

The most effective histidine mutant, M1R56H, P96H, Y102H-neurotensin, caused > 8 °C hypothermia after 25 nmol/kg intravenous injection. Levels of the heterotrimeric construct M1R56H, P96H, Y102H-13A7-13A7 in capillary depleted brain lysates peaked at 1 h and were 60% retained at 8 h. A control construct with no brain targets was only 15% retained at 8 h. Addition of the albumin-binding Nb80 nanobody to make M1R56H, P96H, Y102H-13A7-13A7-Nb80 extended blood half-life from 21 min to 2.6 h. At 30-60 min, biotinylated M1R56H, P96H, Y102H-13A7-13A7-Nb80 was visualized in capillaries using in situ histochemistry, whereas at 2-16 h it was detected in diffuse hippocampal and cortical cellular structures. Levels of M1R56H, P96H, Y102H-13A7-13A7-Nb80 reached more than 3.5 percent injected dose/gram of brain tissue after 30 nmol/kg intravenous injection. However, higher injected concentrations did not result in higher brain levels, compatible with saturation and an apparent substrate inhibitory effect.

CONCLUSION

The pH-sensitive mouse transferrin receptor binding nanobody M1R56H, P96H, Y102H may be a useful tool for rapid and efficient modular transport of diagnostic and therapeutic macromolecular cargos across the blood brain barrier in mouse models. Additional development will be required to determine whether this nanobody-based shuttle system will be useful for imaging and fast-acting therapeutic applications.

Macromolecular Crowding Promotes Re-entrant Liquid-Liquid Phase Separation of Human Serum Transferrin and Prevents Surface-Induced Fibrillation

Protein aggregation and inactivation upon surface immobilization are major limiting factors for analytical applications in biotechnology-related fields. Protein immobilization on solid surfaces often requires multi-step surface passivation, which is time-consuming and inefficient. Herein, we have discovered that biomolecular condensates of biologically active human serum transferrin (Tf) can effectively prevent surface-induced fibrillation and preserve the native-like conformation of phase-separated Tf over a period of 30 days. It has been observed that macromolecular crowding promotes homotypic liquid-liquid phase separation (LLPS) of Tf through enthalpically driven multivalent hydrophobic interactions possibly via the involvement of its low-complexity domain (residues 3-20) containing hydrophobic amino acids. The present LLPS of Tf is a rare example of salt-mediated re-entrant phase separation in a broad range of salt concentrations (0-3 M) solely via the involvement of hydrophobic interactions. Notably, no liquid-to-solid-like phase transition has been observed over a period of 30 days, suggesting the intact conformational integrity of phase-separated Tf, as revealed from single droplet Raman, circular dichroism, and Fourier transform infrared spectroscopy measurements. More importantly, we discovered that the phase-separated condensates of Tf completely inhibit the surface-induced fibrillation of Tf, illustrating the protective role of these liquid-like condensates against denaturation and aggregation of biomolecules. The cell mimicking compact aqueous compartments of biomolecular condensates with a substantial amount of interfacial water preserve the structure and functionality of Tf. Our present study highlights an important functional aspect of biologically active protein condensates and may have wide-ranging implications in cell physiology and biotechnological applications.

Dual-targeted and dual-sensitive self-assembled protein nanocarrier delivering hVEGI-192 for triple-negative breast cancer

Breast cancer is a highly prevalent malignancy worldwide among women with an increasing incidence in recent years. Triple-negative breast cancer (TNBC), a specific type of breast cancer, occurs primarily in young women and exhibits large tumor size, high clinical stage, and extremely poor prognosis with a high rate of lymph node, liver, and lung metastases. TNBC is insensitive to endocrine therapy and trastuzumab treatment, and there is an urgent need for effective therapeutics and treatment guidelines. However, investigations into antiangiogenic agents for the treatment of TNBC are ongoing. In this study, we successfully engineered a self-assembled protein nanocarrier TfRBP9-hVEGI-192-ELP fusion protein (TVEFP) to deliver the therapeutic protein, human vascular endothelial growth inhibitor (hVEGI-192). This was found to be effective in inhibiting tumor angiogenesis in vivo. The protein nanocarrier effectively inhibited the progression of TNBC in vivo and showed the behavior of self-assembly, thermoresponsiveness, enzyme stimulation-responsiveness, tumor-targeting, biocompatibility, and biodegradability. Near-infrared imaging studies showed that fluorescent dye-stained TVEFP effectively aggregated at the tumor site. The TVEFP nanocarrier significantly expands the application of the therapeutic protein hVEGI-192 and improves the imaging and biotherapeutic effects in TNBC, chiefly based on anti-angiogenesis effects.

Basic mechanisms and novel potential therapeutic targets for ferroptosis in acute myeloid leukemia

Ferroptosis is a form of cell death that is regulated by iron and characterized by the buildup of lipid peroxides (LPO) and subsequent rupture of the cell membrane. The molecular mechanisms of ferroptosis involve metabolic pathways related to iron, lipids, and amino acids, which contribute to the production of lipid reactive oxygen species (ROS). In recent years, there has been increasing attention on the occurrence of ferroptosis in various diseases. Ferroptosis has been found to play a crucial role in cardiovascular diseases, digestive diseases, respiratory and immunological diseases, and particularly in malignancies. However, there is still a lack of studies on ferroptosis in acute myeloid leukemia (AML). This paper provides a comprehensive review of the mechanism of ferroptosis and its regulatory molecules and therapeutic agents in AML. It also evaluates the relationship between ferroptosis-related genes (FRGs), non-coding RNAs (ncRNAs), and prognosis to develop prognostic molecular models in AML. The study also explores the association between ferroptosis and immune infiltration in AML, to identify novel potential target regimens for AML.

The emerging role of N6-methyladenine RNA methylation in metal ion metabolism and metal-induced carcinogenesis

N⁶-methyladenine (m⁶A) is the most common and abundant internal modification in eukaryotic mRNAs, which can regulate gene expression and perform important biological tasks. Metal ions participate in nucleotide biosynthesis and repair, signal transduction, energy generation, immune defense, and other important metabolic processes. However, long-term environmental and occupational exposure to metals through food, air, soil, water, and industry can result in toxicity, serious health problems, and cancer. Recent evidence indicates dynamic and reversible m⁶A modification modulates various metal ion metabolism, such as iron absorption, calcium uptake and transport. In turn, environmental heavy metal can alter m⁶A modification by directly affecting catalytic activity and expression level of methyltransferases and demethylases, or through reactive oxygen species, eventually disrupting normal biological function and leading to diseases. Therefore, m⁶A RNA methylation may play a bridging role in heavy metal pollution-induced carcinogenesis. This review discusses interaction among heavy metal, m⁶A, and metal ions metabolism, and their regulatory mechanism, focuses on the role of m⁶A methylation and heavy metal pollution in cancer. Finally, the role of nutritional therapy that targeting m⁶A methylation to prevent metal ion metabolism disorder-induced cancer is summarized.

Ferritinophagy-mediated iron competition in RUTIs: Tug-of-war between UPEC and host

Uropathogenic Escherichia coli (UPEC) is the main pathogen of recurrent urinary tract infections (RUTIs). Urinary tract infection is a complicated interaction between UPEC and the host. During infection, UPEC can evade the host's immune response and retain in bladder epithelial cells, which requires adequate nutritional support. Iron is the first necessary trace element in life and a key nutritional factor, making it an important part of the competition between UPEC and the host. On the one hand, UPEC grabs iron to satisfy its reproduction, on the other hand, the host relies on iron to build nutritional immunity defenses against UPEC. Ferritinophagy is a selective autophagy of ferritin mediated by nuclear receptor coactivator 4, which is not only a way for the host to regulate iron metabolism to maintain iron homeostasis, but also a key point of competition between the host and UPEC. Although recent studies have confirmed the role of ferritinophagy in the progression of many diseases, the mechanism of potential interactions between ferritinophagy in UPEC and the host is poorly understood. In this paper, we reviewed the potential mechanisms of ferritinophagy-mediated iron competition in the UPEC-host interactions. This competitive relationship, like a tug-of-war, is a confrontation between the capability of UPEC to capture iron and the host's nutritional immunity defense, which could be the trigger for RUTIs. Therefore, understanding ferritinophagy-mediated iron competition may provide new strategies for exploring effective antibiotic alternative therapies to prevent and treat RUTIs.

HWJMSC-derived extracellular vesicles ameliorate IL-1β-induced chondrocyte injury through regulation of the BMP2/RUNX2 axis via up-regulation TFRC

Articular osteochondral injury is a common and frequently occurring disease in orthopedics that is caused by aging, disease, and trauma. The cytokine interleukin-1β (IL-1β) is a crucial mediator of the inflammatory response, which exacerbates damage during chronic disease and acute tissue injury. Human Wharton's jelly mesenchymal stem cell (HWJMSC) extracellular vesicles (HWJMSC-EVs) have been shown to promote cartilage regeneration. The study aimed to investigate the influence and mechanisms of HWJMSC-EVs on the viability, apoptosis, and cell cycle of IL-1β-induced chondrocytes. HWJMSC-EVs were isolated by Ribo™ Exosome Isolation Reagent kit. Nanoparticle tracking analysis was used to determine the size and concentration of HWJMSC-EVs. We characterized HWJMSC-EVs by western blot and transmission electron microscope. The differentiation, viability, and protein level of chondrocytes were measured by Alcian blue staining, Cell Counting Kit-8, and western blot, respectively. Flow cytometer was used to determine apoptosis and cell cycle of chondrocytes. The results showed that HWJMSCs relieved IL-1β-induced chondrocyte injury by inhibiting apoptosis and elevating viability and cell cycle of chondrocyte, which was reversed with exosome inhibitor (GW4869). HWJMSC-EVs were successfully extracted and proven to be uptake by chondrocytes. HWJMSC-EVs ameliorate IL-1β-induced chondrocyte injury by inhibiting cell apoptosis and elevating viability and cycle of cell, but these effects were effectively reversed by knockdown of transferrin receptor (TFRC). Notably, using bone morphogenetic protein 2 (BMP2) pathway agonist and inhibitor suggested that HWJMSC-EVs ameliorate IL-1β-induced chondrocyte injury through activating the BMP2 pathway via up-regulation TFRC. Furthermore, over-expression of runt-related transcription factor 2 (RUNX2) reversed the effects of BMP2 pathway inhibitor promotion of IL-1β-induced chondrocyte injury. These results suggested that HWJMSC-EVs ameliorate IL-1β-induced chondrocyte injury by regulating the BMP2/RUNX2 axis via up-regulation TFRC. HWJMSC-EVs may play a new insight for early medical interventions in patients with articular osteochondral injury.

Enhanced in Vivo Blood Brain Barrier Transcytosis of Macromolecular Cargo Using an Engineered pH-sensitive Mouse Transferrin Receptor Binding Nanobody

Background

The blood brain barrier limits entry of macromolecular diagnostic and therapeutic cargos. Blood brain barrier transcytosis via receptor mediated transport systems, such as the transferrin receptor, can be used to carry macromolecular cargos with variable efficiency. Transcytosis involves trafficking through acidified intracellular vesicles, but it is not known whether pH-dependent unbinding of transport shuttles can be used to improve blood brain barrier transport efficiency.

Methods

A mouse transferrin receptor binding nanobody, NIH-mTfR-M1, was engineered to confer greater unbinding at pH 5.5 vs 7.4 by introducing multiple histidine mutations. The histidine mutant nanobodies were coupled to neurotensin for in vivo functional blood brain barrier transcytosis testing via central neurotensin-mediated hypothermia in wild-type mice. Multi-nanobody constructs including the mutant M1 R56H, P96H, Y102H and two copies of the P2X7 receptor-binding 13A7 nanobody were produced to test proof-of-concept macromolecular cargo transport in vivo using quantitatively verified capillary depleted brain lysates and in situ histology.

Results

The most effective histidine mutant, M1 R56H, P96H, Y102H -neurotensin, caused >8°C hypothermia after 25 nmol/kg intravenous injection. Levels of the heterotrimeric construct M1 56,96,102His -13A7-13A7 in capillary depleted brain lysates peaked at 1 hour and were 60% retained at 8 hours. A control construct with no brain targets was only 15% retained at 8 hours. Addition of the albumin-binding Nb80 nanobody to make M1 R56H, P96H, Y102H -13A7-13A7-Nb80 extended blood half-life from 21 minutes to 2.6 hours. At 30-60 minutes, biotinylated M1 R56H, P96H, Y102H -13A7-13A7-Nb80 was visualized in capillaries using in situ histochemistry, whereas at 2-16 hours it was detected in diffuse hippocampal and cortical cellular structures. Levels of M1 R56H, P96H, Y102H -13A7-13A7-Nb80 reached more than 3.5 percent injected dose/gram of brain tissue after 30 nmol/kg intravenous injection. However, higher injected concentrations did not result in higher brain levels, compatible with saturation and an apparent substrate inhibitory effect.

Conclusion

The pH-sensitive mouse transferrin receptor binding nanobody M1 R56H, P96H, Y102H may be a useful tool for rapid and efficient modular transport of diagnostic and therapeutic macromolecular cargos across the blood brain barrier in mouse models. Additional development will be required to determine whether this nanobody-based shuttle system will be useful for imaging and fast-acting therapeutic applications.

Expression of TFRC helps to improve the antineoplastic effect of Ara-C on AML cells through a targeted delivery carrier

BACKGROUND

Currently, high doses of cytarabine arabinoside (Ara-C)-based combined chemotherapy are commonly used in acute myeloid leukemia (AML) therapy, but severe adverse effects and poor suppression effects in leukemia cells limit the clinical therapeutic efficiency of Ara-C-based chemotherapy due to a lack of targeting selectivity. To improve the therapeutic effect of Ara-C in AML, here, since we confirmed that transferrin receptor 1 (TFRC) expression in AML cells was constant, we generated Ara-C@HFn by encapsulating free Ara-C into self-assembled heavy ferritin chain (HFn, the ligand of TFRC) nanocages.

RESULTS

The analysis of clinically relevant data suggested that the high expression levels of TFRC from AML cells would not decrease significantly after treatment with Ara-C. Ara-C@HFn can be efficiently internalized by leukemia cells, showing stronger cytotoxic effects in vitro and reducing the burden of leukemia in AML mice more effectively in vivo than free Ara-C. Ara-C@HFn treatment showed no acute toxicity in visceral organs of mice. Moreover, the analysis of clinically relevant data also suggested that there are several drugs (such as tamibarotene and ABT199) that would not cause significant expression down-regulation of TFRC in AML cells (after treatment).

CONCLUSION

The above results suggested that TFRC can be used as a constant and effective target for drug targeting delivery of AML cells. Thus Ara-C@HFn treatment can become a safe and efficient strategy for AML therapy by specifically delivering Ara-C to AML cells. Besides, the HFn nanocages are promising for improving antineoplastic effect of other AML-related therapy drugs that do not cause downregulated expression of TFRC in AML cells.

Label-Free Mass Spectrometry Proteomics Reveals Different Pathways Modulated in THP-1 Cells Infected with Therapeutic Failure and Drug Resistance Leishmania infantum Clinical Isolates

As the world is facing increasing difficulties to treat leishmaniasis with current therapies, deeper investigation into the molecular mechanisms responsible for both drug resistance and treatment failure (TF) is essential in drug discovery and development. So far, few available drugs cause severe side effects and have developed several resistance mechanisms. Drug resistance and TF parasite strains from clinical isolates may have acquired altered expression of proteins that characterize specific mechanisms leading to therapy inefficacy. This work aims to identify the biochemical pathways of THP-1 human monocytes infected by different Leishmania infantum clinical isolates from patients with either resistance or with TF outcome, using whole cell differential Mass Spectrometry proteomics. We have adopted network enrichment analysis to integrate the transcriptomics and the proteomic results of infected cells studies. Transferrin receptor C (TFRC) and nucleoside diphosphate kinase 3 (NDK3) were discovered as overexpressed proteins in THP-1 cells infected with paromomycin, antimony, and miltefosine resistant L. infantum lines. The overall achievements represent founding concepts to confirm new targets involved in the parasitic drug resistance and TF mechanisms, and to consider in perspective the importance of a dual host-guest pharmacological approach to treat the acute stage of the disease.

Use of a solid-state nanopore for profiling the transferrin receptor protein and distinguishing between transferrin receptor and its ligand protein

A nanopore device is capable of providing single-molecule level information of an analyte as they translocate through the sensing aperture-a nanometer-sized through-hole-under the influence of an applied electric field. In this study, a silicon nitride (Six Ny )-based nanopore was used to characterize the human serum transferrin receptor protein (TfR) under various applied voltages. The presence of dimeric forms of TfR was found to decrease exponentially as the applied electric field increased. Further analysis of monomeric TfR also revealed that its unfolding behaviors were positively dependent on the applied voltage. Furthermore, a comparison between the data of monomeric TfR and its ligand protein, human serum transferrin (hSTf), showed that these two protein populations, despite their nearly identical molecular weights, could be distinguished from each other by means of a solid-state nanopore (SSN). Lastly, the excluded volumes of TfR were experimentally determined at each voltage and were found to be within error of their theoretical values. The results herein demonstrate the successful application of an SSN for accurately classifying monomeric and dimeric molecules while the two populations coexist in a heterogeneous mixture.

Review of the Role of Ferroptosis in Testicular Function

Iron is an important metal element involved in the regulation of male reproductive functions and has dual effects on testicular tissue. A moderate iron content is necessary to maintain testosterone synthesis and spermatogenesis. Iron overload can lead to male reproductive dysfunction by triggering testicular oxidative stress, lipid peroxidation, and even testicular ferroptosis. Ferroptosis is an iron-dependent form of cell death that is characterized by iron overload, lipid peroxidation, mitochondrial damage, and glutathione peroxidase depletion. This review summarizes the regulatory mechanism of ferroptosis and the research progress on testicular ferroptosis caused by endogenous and exogenous toxicants. The purpose of the present review is to provide a theoretical basis for the relationship between ferroptosis and male reproductive function. Some toxic substances or danger signals can cause male reproductive dysfunction by inducing testicular ferroptosis. It is crucial to deeply explore the testicular ferroptosis mechanism, which will help further elucidate the molecular mechanism of male reproductive dysfunction. It is worth noting that ferroptosis does not exist alone but rather coexists with other forms of cell death (such as apoptosis, necrosis, and autophagic death). Alleviating ferroptosis alone may not completely reverse male reproductive dysfunction caused by various risk factors.

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.

The analysis of the relationship between transferrin receptor 1 (TfR1) and clinical, morphological and immunophenotypic characteristics of breast cancer: retrospective cohort study

Background. Transferrin receptor 1 (TfR1) expression has been identified in a number of malignant tumors. It is noted that its overexpression gives growth advantages to cancer cells. Estimation of transferrin receptor expression in breast cancer (BC) might be an important component in disease prognosis, choice of treatment, also might be an attractive target for targeted therapy. Aim. To evaluate the expression of TfR1 by BC cells and to study its relationship with the clinical, morphological and immunophenotypic characteristics of the tumor. Materials and methods. This study included 82 patients with BC who received treatment at the Blokhin National Medical Research Center of Oncology (Moscow). The expression of TfR1 on primary tumor cells was studied, the relationship of TfR1 with clinical, morphological and immunophenotypic characteristics of BC was analyzed. Immunophenotyping of the primary tumor was performed by the immunohistochemical method (immunofluorescent staining) on cryostat sections. Antibodies to CD71, CD95, CD54, CD29, MUC1, Pgp170 were used. The reaction was evaluated using a luminescent microscope (AXIOSKOP, Germany). The study was dominated by patients with stage IIB 54% and IIIB 21%. Infiltrative ductal BC was diagnosed in 67% (n=55) of patients, infiltrative-lobular in 22% (n=18) of cases, other types in 11.0% (n=9). Results. BC cells expressed TfR1 in most cases (64.4%; n=61). A combination of TfR1 monomorphic expression with MUC1 monomorphic expression (74.4%; n=47) was noted. CD29 is presented both mosaic (38.7%) and monomorphic (51.6%). The Pgp170 antigen was monomorphically observed in 27.5% of cases. As the proportion of TfR+ cells increased, the expression frequency of the adhesion molecule CD54 increased from 10.5 to 33.3%, a positive correlation was established (r=0.293; p=0.008). In the group with TfR1 monomorphic expression, the frequency of tumors expressing the CD95 apoptosis molecule decreased: 25.0% vs 13% (p=0.042). Conclusion. BC cells overexpress TfR1. TfR1 expression is associated with tumor immunophenotype.

Influence of Protein Carbonylation on Human Adipose Tissue Dysfunction in Obesity and Insulin Resistance

BACKGROUND

Obesity is characterized by adipose tissue dysregulation and predisposes individuals to insulin resistance and type 2 diabetes. At the molecular level, adipocyte dysfunction has been linked to obesity-triggered oxidative stress and protein carbonylation, considering protein carbonylation as a link between oxidative stress and metabolic dysfunction. The identification of specific carbonylated proteins in adipose tissue could provide novel biomarkers of oxidative damage related to metabolic status (i.e prediabetes). Thus, we aimed at characterizing the subcutaneous and omental human adipose tissue carbonylome in obesity-associated insulin resistance.

METHODS

2D-PAGE was used to identify carbonylated proteins, and clinical correlations studies and molecular biology approaches including intracellular trafficking, reactive oxygen species assay, and iron content were performed using in vitro models of insulin resistance.

RESULTS

The carbonylome of human adipose tissue included common (serotransferrin, vimentin, actin, and annexin A2) and depot-specific (carbonic anhydrase and α-crystallin B in the subcutaneous depot; and α-1-antitrypsin and tubulin in the omental depot) differences that point out the complexity of oxidative stress at the metabolic level, highlighting changes in carbonylated transferrin expression. Posterior studies using in vitro prediabetic model evidence alteration in transferrin receptor translocation, linked to the prediabetic environment. Finally, ligand-receptor molecular docking studies showed a reduced affinity for carbonylated transferrin binding to its receptor compared to wild-type transferrin, emphasizing the role of transferrin carbonylation in the link between oxidative stress and metabolic dysfunction.

CONCLUSIONS

The adipose tissue carbonylome contributes to understanding the molecular mechanism driving adipocyte dysfunction and identifies possible adipose tissue carbonylated targets in obesity-associated insulin resistance.

Iron Homeostasis and Energy Metabolism in Obesity

Iron plays a role in energy metabolism as a component of vital enzymes and electron transport chains (ETCs) for adenosine triphosphate (ATP) synthesis. The tricarboxylic acid (TCA) cycle and oxidative phosphorylation are crucial in generating ATP in mitochondria. At the mitochondria matrix, heme and iron-sulfur clusters are synthesized. Iron-sulfur cluster is a part of the aconitase in the TCA cycle and a functional or structural component of electron transfer proteins. Heme is the prosthetic group for cytochrome c, a principal component of the respiratory ETC. Regarding fat metabolism, iron regulates mitochondrial fat oxidation and affects the thermogenesis of brown adipose tissue (BAT). Thermogenesis is a process that increases energy expenditure, and BAT is a tissue that generates heat via mitochondrial fuel oxidation. Iron deficiency may impair mitochondrial fuel oxidation by inhibiting iron-containing molecules, leading to decreased energy expenditure. Although it is expected that impaired mitochondrial fuel oxidation may be restored by iron supplementation, its underlying mechanisms have not been clearly identified. Therefore, this review summarizes the current evidence on how iron regulates energy metabolism considering the TCA cycle, oxidative phosphorylation, and thermogenesis. Additionally, we relate iron-mediated metabolic regulation to obesity and obesity-related complications.

The effect of narcotics on ferroptosis-related molecular mechanisms and signalling pathways

Ferroptosis is a novel programmed cell death form characterized by iron-mediated reactive oxygen species-induced lipid peroxidation and subsequent cell damage that is distinct from apoptosis, necroptosis, pyroptosis, and autophagy. Most studies on ferroptosis are based on its function and mechanism, but there have been relatively few studies on the effects of drugs, especially anaesthetics, on ferroptosis. Therefore, we summarized the recent literature on the effects of anaesthetics on ferroptosis to understand the underlying mechanism. In particular, we focused on the targets of various anaesthetics in different mechanisms of ferroptosis and the effects of ferroptosis induction or inhibition by narcotics on various diseases. The aims of this review are to provide a relatively reasonable drug regimen for clinicians, to explore potential ferroptosis protection drugs and targets, to reduce perioperative complications and to improve the postoperative performance of patients, especially those who are critically ill.

Bioinformatic Analysis of the Genetic Mechanism of Biomineralization of Biogenic Magnetic Nanoparticles in Bacteria Capable of Tumor-Specific Accumulation

Background. Current methods of targeted cancer therapy are not always effective enough and can lead to side effects, such as an increased risk of autoimmune diseases. It is known that some bacteria are capable of specific accumulation in malignant tumors, and therefore can be used as an alternative means of targeted drug delivery. However, the genetic mechanism of tumor-specific accumulation of bacteria is not fully understood and needs to be studied in more detail. Objective. This work aims to identify, by methods of comparative genomics methods, magnetically controlled bacteria among those for which tumor-specific accumulation has already been experimentally shown. Methods. To identify magnetically controlled bacterial strains, i.e., bacteria that biomineralize biogenic magnetic nanoparticles (BMN), the method of comparative genomics was used, namely: pairwise alignment of proteomes with amino acid sequences of Mam-proteins of required for biomineralization of BMN in magneto­tactic bacteria Magnetospirillum gryphiswaldense MSR-1. Sequence alignments were performed in the BLAST program of the US National Center for Biotechnology Information (NCBI). Results. The conducted bioinformatic analysis showed that strains of bacteria in which the ability to accumulate specifically in tumors has been experimentally proven are potential producers of BMN of different types. Among them there are potential producers of intracellular crystalline BMN, potential producers of intracellular amorphous BMN, and extracellular crystalline BMN Conclusions. It is expedient to use bacteria-producing BMN as gene vectors and systems of targeted drug delivery to tumors that biomineralize BMN.

Environmental and occupational exposure of metals and female reproductive health

Untainted environment promotes health, but the last few decades experienced steep upsurge in environmental contaminants posing detrimental physiological impact. The responsible factors mainly include the exponential growth of human population, havoc rise in industrialization, poorly planned urbanization, and slapdash environment management. Environmental degradation can increase the likelihood of human exposure to heavy metals, resulting in health consequences such as reproductive problems. As a result, research into metal-induced causes of reproductive impairment at the genetic, epigenetic, and biochemical levels must be strengthened further. These metals impact upon the female reproduction at all strata of its regulation and functions, be it development, maturation, or endocrine functions, and are linked to an increase in the causes of infertility in women. Chronic exposures to the heavy metals may lead to breast cancer, endometriosis, endometrial cancer, menstrual disorders, and spontaneous abortions, as well as pre-term deliveries, stillbirths. For example, endometriosis, endometrial cancer, and spontaneous abortions are all caused by the metalloestrogen cadmium (Cd); lead (Pb) levels over a certain threshold can cause spontaneous abortion and have a teratogenic impact; toxic amounts of mercury (Hg) have an influence on the menstrual cycle, which can lead to infertility. Impact of environmental exposure to heavy metals on female fertility is therefore a well-known fact. Thus, the underlying mechanisms must be explained and periodically updated, given the growing evidence on the influence of increasing environmental heavy metal load on female fertility. The purpose of this review is to give a concise overview of how heavy metal affects female reproductive health.

Ubiquitin ligase E3 HUWE1/MULE targets transferrin receptor for degradation and suppresses ferroptosis in acute liver injury

Hepatic ischemia followed by reperfusion (I/R), a major clinical problem during liver surgical procedures, can induce liver injury with severe cell death including ferroptosis which is characterized by iron-dependent accumulation of lipid peroxidation. The HECT domain-containing ubiquitin E3 ligase HUWE1 (also known as MULE) was initially shown to promote apoptosis. However, our preliminary study demonstrates that high expression of HUWE1 in the liver donors corelates with less injury and better hepatic function after liver transplantation in patients. Thus, we investigate the role of HUWE1 in acute liver injury, and identify HUWE1 as a negative ferroptosis modulator through transferrin receptor 1(TfR1). Deficiency of Huwe1 in mice hepatocytes (HKO) exacerbated I/R and CCl4-induced liver injury with more ferroptosis occurrence. Moreover, Suppression of Huwe1 remarkably enhances cellular sensitivity to ferroptosis in primary hepatocytes and mouse embryonic fibroblasts. Mechanistically, HUWE1 specifically targets TfR1 for ubiquitination and proteasomal degradation, thereby regulates iron metabolism. Importantly, chemical and genetic inhibition of TfR1 dramatically diminishes the ferroptotic cell death in Huwe1 KO cells and Huwe1 HKO mice. Therefore, HUWE1 is a potential protective factor to antagonize both aberrant iron accumulation and ferroptosis thereby mitigating acute liver injury. These findings may provide clinical implications for patients with the high-expression Huwe1 alleles.

Iron Metabolism and Ferroptosis in Physiological and Pathological Pregnancy

Iron is a vital element in nearly every living organism. During pregnancy, optimal iron concentration is essential for both maternal health and fetal development. As the barrier between the mother and fetus, placenta plays a pivotal role in mediating and regulating iron transport. Imbalances in iron metabolism correlate with severe adverse pregnancy outcomes. Like most other nutrients, iron exhibits a U-shaped risk curve. Apart from iron deficiency, iron overload is also dangerous since labile iron can generate reactive oxygen species, which leads to oxidative stress and activates ferroptosis. In this review, we summarized the molecular mechanism and regulation signals of placental iron trafficking under physiological conditions. In addition, we revealed the role of iron metabolism and ferroptosis in the view of preeclampsia and gestational diabetes mellitus, which may bring new insight to the pathogenesis and treatment of pregnancy-related diseases.

G-Quadruplex-Proximized Aptamers (G4PA) Efficiently Targeting Cell-Surface Transferrin Receptors for Targeted Cargo Delivery

DNA-assembled multiaptamer systems have been demonstrated to significantly promote the aptamer capacity of binding cell-surface-expressed proteins. However, how to conveniently harness them for efficient transmembrane delivery of targets remains a challenge. Toward this goal, here we engineer a G-quadruplex-proximized aptamer (G4PA) system in which a DNA aptamer specific for transferrin receptor (TfR) is guided by a bimolecular G4 and assembles into a dimerized proximity form that well matches homodimeric TfR highly expressed on the cancer cell surface. This system displays a higher capacity for targeting cell-surface TfR than the monomeric aptamer and super transmembrane transportation of nucleic acid cargoes, which is comparable to that of conventional liposome transfection but overcomes the lack of targeting ability of the latter. The G4PA system is then applied to the targeted delivery of siRNA for PLK1 gene silencing in positive cells rather than negative controls, showing great promise for use in precise anticancer therapy.

Discovery of a Transferrin Receptor 1-Binding Aptamer and Its Application in Cancer Cell Depletion for Adoptive T-Cell Therapy Manufacturing

The clinical manufacturing of chimeric antigen receptor (CAR) T cells includes cell selection, activation, gene transduction, and expansion. While the method of T-cell selection varies across companies, current methods do not actively eliminate the cancer cells in the patient's apheresis product from the healthy immune cells. Alarmingly, it has been found that transduction of a single leukemic B cell with the CAR gene can confer resistance to CAR T-cell therapy and lead to treatment failure. In this study, we report the identification of a novel high-affinity DNA aptamer, termed tJBA8.1, that binds transferrin receptor 1 (TfR1), a receptor broadly upregulated by cancer cells. Using competition assays, high resolution cryo-EM, and de novo model building of the aptamer into the resulting electron density, we reveal that tJBA8.1 shares a binding site on TfR1 with holo-transferrin, the natural ligand of TfR1. We use tJBA8.1 to effectively deplete B lymphoma cells spiked into peripheral blood mononuclear cells with minimal impact on the healthy immune cell composition. Lastly, we present opportunities for affinity improvement of tJBA8.1. As TfR1 expression is broadly upregulated in many cancers, including difficult-to-treat T-cell leukemias and lymphomas, our work provides a facile, universal, and inexpensive approach for comprehensively removing cancerous cells from patient apheresis products for safe manufacturing of adoptive T-cell therapies.

Intracellular Iron Binding and Antioxidant Activity of Phytochelators

Phytochelators have been studied as templates for designing new drugs for chelation therapy. This work evaluated key chemical and biological properties of five candidate phytochelators for iron overload diseases: maltol, mimosine, morin, tropolone, and esculetin. Intra- and extracellular iron affinity and antioxidant activity, as well as the ability to scavenge iron from holo-transferrin, were studied in physiologically relevant settings. Tropolone and mimosine (and, to a lesser extent, maltol) presented good binding capacity for iron, removing it from calcein, a high-affinity fluorescent probe. Tropolone and mimosine arrested iron-mediated oxidation of ascorbate with the same efficiency as the standard iron chelator DFO. Also, both were cell permeant and able to access labile pools of iron in HeLa and HepG2 cells. Mimosine was an effective antioxidant in cells stressed by iron and peroxide, being as efficient as the cell-permeant iron chelator deferiprone. These results reinforce the potential of those molecules, especially mimosine, as adjuvants in treatments for iron overload.

Integrating intracellular nanovesicles into integrin trafficking pathways and beyond

Membrane traffic controls the movement of proteins and lipids from one cellular compartment to another using a system of transport vesicles. Intracellular nanovesicles (INVs) are a newly described class of transport vesicles. These vesicles are small, carry diverse cargo, and are involved in multiple trafficking steps including anterograde traffic and endosomal recycling. An example of a biological process that they control is cell migration and invasion, due to their role in integrin recycling. In this review, we describe what is known so far about these vesicles. We discuss how INVs may integrate into established membrane trafficking pathways using integrin recycling as an example. We speculate where in the cell INVs have the potential to operate and we identify key questions for future investigation.

Identification and Tetramer Structure of Hemin-Binding Protein SPD_0310 Linked to Iron Homeostasis and Virulence of Streptococcus pneumoniae

Iron and iron-containing compounds are essential for bacterial virulence and host infection. Hemin is an important supplement compound for bacterial survival in an iron-deficient environment. Despite strong interest in hemin metabolism, the detailed mechanism of hemin transportation in Gram-positive bacteria is yet to be reported. The results of our study revealed that the homologous proteins of SPD_0310 were significantly conservative in Gram-positive bacteria (P < 0.001), and these proteins were identified as belonging to an uncharacterized protein family (UPF0371). The results of thermodynamic and kinetic studies have shown that SPD_0310 has a high hemin-binding affinity. Interestingly, we found that the crystal structure of SPD_0310 presented a homotetramer conformation, which is required for hemin binding. SPD_0310 can interact with many hemin-binding proteins (SPD_0090, SPD_1609, and GAPDH) located on the cell surface, which contributes to hemin transfer to the cytoplasm. It also has a high affinity with other iron transporters in the cytoplasm (SPD_0226 and SPD_0227), which facilitates iron redistribution in cells. More importantly, the knockout of the spd_0310 gene (Δspd_0310) resulted in a decrease in the iron content and protein expression levels of many bacterial adhesion factors. Moreover, the animal model showed that the Δspd_0310 strain has a lower virulence than the wild type. Based on the crystallographic and biochemical studies, we inferred that SPD_0310 is a hemin intermediate transporter which contributes to iron homeostasis and further affects the virulence of Streptococcus pneumoniae in the host. Our study provides not only an important theoretical basis for the in-depth elucidation of the hemin transport mechanism in bacteria but also an important candidate target for the development of novel antimicrobial agents based on metal transport systems. IMPORTANCE Iron is an essential element for bacterial virulence and infection of the host. The detailed hemin metabolism in Gram-positive bacteria has rarely been studied. SPD_0310 belongs to the UPF0371 family of proteins, and results of homology analysis and evolutionary tree analysis suggested that it was widely distributed and highly conserved in Gram-positive bacteria. However, the function of the UPF0371 family remains unknown. We successfully determined the crystal structure of apo-SPD_0310, which is a homotetramer. We found that cytoplasmic protein SPD_0310 with a special tetramer structure has a strong hemin-binding ability and interacts with many iron transporters, which facilitates hemin transfer from the extracellular space to the cytoplasm. The results of detailed functional analyses indicated that SPD_0310 may function as a hemin transporter similar to hemoglobin in animals and contributes to bacterial iron homeostasis and virulence. This study provides a novel target for the development of antimicrobial drugs against pathogenic Gram-positive bacteria.

Organelle transporters and inter-organelle communication as drivers of metabolic regulation and cellular homeostasis

Background

Spatial compartmentalization of metabolic pathways within membrane-separated organelles is key to the ability of eukaryotic cells to precisely regulate their biochemical functions. Membrane-bound organelles such as mitochondria, endoplasmic reticulum (ER) and lysosomes enable the concentration of metabolic precursors within optimized chemical environments, greatly accelerating the efficiency of both anabolic and catabolic reactions, enabling division of labor and optimal utilization of resources. However, metabolic compartmentalization also poses a challenge to cells because it creates spatial discontinuities that must be bridged for reaction cascades to be connected and completed. To do so, cells employ different methods to coordinate metabolic fluxes occurring in different organelles, such as membrane-localized transporters to facilitate regulated metabolite exchange between mitochondria and lysosomes, non-vesicular transport pathways via physical contact sites connecting the ER with both mitochondria and lysosomes, as well as localized regulatory signaling processes that coordinately regulate the activity of all these organelles.

Scope of review

This review covers how cells use membrane transporters, membrane contact sites, and localized signaling pathways to mediate inter-organelle communication and coordinate metabolism. We also describe how disruption of inter-organelle communication is an emerging driver in a multitude of diseases, from cancer to neurodegeneration.

Major conclusions

Effective communication among organelles is essential to cellular health and function. Identifying the major molecular players involved in mediating metabolic coordination between organelles will further our understanding of cellular metabolism in health and lead us to design better therapeutics against dysregulated metabolism in disease.

Transferrin receptor 1 promotes the fibroblast growth factor receptor-mediated oncogenic potential of diffused-type gastric cancer

Diffuse-type gastric cancer (DGC) is a highly invasive subtype of gastric adenocarcinoma that frequently exhibits scattered peritoneal metastasis. Previous studies have shown that the genes of receptor tyrosine kinases (RTKs), such as fibroblast growth factor receptor 2 (FGFR2) or Met, are amplified in some DGC cell lines, leading to the constitutive activation of corresponding RTKs. In these cell lines, the survival of cancer cells appears to be dependent on the activation of RTKs. To gain novel insights into the downstream signaling pathways of RTKs specific to DGC, phosphotyrosine-containing proteins associated with activated FGFR2 were purified through two sequential rounds of immunoprecipitation from the lysates of two DGC cell lines. As a result, transferrin receptor 1 (TfR1) was identified as the binding partner of FGFR2. Biochemical analysis confirmed that TfR1 protein binds to FGFR2 and is phosphorylated at tyrosine 20 (Tyr20) in an FGFR2 kinase activity-dependent manner. The knockdown of TfR1 and treatment with an inhibitor of FGFR2 caused significant impairment in iron uptake and suppression of cellular proliferation in vitro. Moreover, the suppression of expression levels of TfR1 in the DGC cells significantly reduced their tumorigenicity and potency of peritoneal dissemination. It was indicated that TfR1, when phosphorylated by the binding partner FGFR2 in DGC cells, promotes proliferation and tumorigenicity of these cancer cells. These results suggest that the control of TfR1 function may serve as a therapeutic target in DGC with activated FGFR2.