-
International Journal of Molecular... Apr 2021Iron is a critical metal for several vital biological processes. Most of the body's iron is bound to hemoglobin in erythrocytes. Iron from senescent red blood cells is... (Review)
Review
Iron is a critical metal for several vital biological processes. Most of the body's iron is bound to hemoglobin in erythrocytes. Iron from senescent red blood cells is recycled by macrophages in the spleen, liver and bone marrow. Dietary iron is taken up by the divalent metal transporter 1 (DMT1) in enterocytes and transported to portal blood via ferroportin (FPN), where it is bound to transferrin and taken up by hepatocytes, macrophages and bone marrow cells via transferrin receptor 1 (TfR1). While most of the physiologically active iron is bound hemoglobin, the major storage of most iron occurs in the liver in a ferritin-bound fashion. In response to an increased iron load, hepatocytes secrete the peptide hormone hepcidin, which binds to and induces internalization and degradation of the iron transporter FPN, thus controlling the amount of iron released from the cells into the blood. This review summarizes the key mechanisms and players involved in cellular and systemic iron regulation.
Topics: Animals; Cation Transport Proteins; Enterocytes; Ferritins; Hemoglobins; Hepatocytes; Humans; Iron; Iron, Dietary; Liver; Receptors, Transferrin; Spleen; Transferrin
PubMed: 33925597
DOI: 10.3390/ijms22094591 -
Nature Aug 2020The majority of therapies that target individual proteins rely on specific activity-modulating interactions with the target protein-for example, enzyme inhibition or...
The majority of therapies that target individual proteins rely on specific activity-modulating interactions with the target protein-for example, enzyme inhibition or ligand blocking. However, several major classes of therapeutically relevant proteins have unknown or inaccessible activity profiles and so cannot be targeted by such strategies. Protein-degradation platforms such as proteolysis-targeting chimaeras (PROTACs) and others (for example, dTAGs, Trim-Away, chaperone-mediated autophagy targeting and SNIPERs) have been developed for proteins that are typically difficult to target; however, these methods involve the manipulation of intracellular protein degradation machinery and are therefore fundamentally limited to proteins that contain cytosolic domains to which ligands can bind and recruit the requisite cellular components. Extracellular and membrane-associated proteins-the products of 40% of all protein-encoding genes-are key agents in cancer, ageing-related diseases and autoimmune disorders, and so a general strategy to selectively degrade these proteins has the potential to improve human health. Here we establish the targeted degradation of extracellular and membrane-associated proteins using conjugates that bind both a cell-surface lysosome-shuttling receptor and the extracellular domain of a target protein. These initial lysosome-targeting chimaeras, which we term LYTACs, consist of a small molecule or antibody fused to chemically synthesized glycopeptide ligands that are agonists of the cation-independent mannose-6-phosphate receptor (CI-M6PR). We use LYTACs to develop a CRISPR interference screen that reveals the biochemical pathway for CI-M6PR-mediated cargo internalization in cell lines, and uncover the exocyst complex as a previously unidentified-but essential-component of this pathway. We demonstrate the scope of this platform through the degradation of therapeutically relevant proteins, including apolipoprotein E4, epidermal growth factor receptor, CD71 and programmed death-ligand 1. Our results establish a modular strategy for directing secreted and membrane proteins for lysosomal degradation, with broad implications for biochemical research and for therapeutics.
Topics: Animals; Antibodies; Antigens, CD; Apolipoprotein E4; B7-H1 Antigen; CRISPR-Cas Systems; Cell Line; ErbB Receptors; Extracellular Space; Female; Glycopeptides; Humans; Ligands; Lysosomes; Membrane Proteins; Mice; Protein Domains; Protein Transport; Proteolysis; Receptor, IGF Type 2; Receptors, Transferrin; Recombinant Fusion Proteins; Solubility; Substrate Specificity
PubMed: 32728216
DOI: 10.1038/s41586-020-2545-9 -
Cell Reports Mar 2020Ferroptosis is a type of regulated cell death driven by the iron-dependent accumulation of oxidized polyunsaturated fatty acid-containing phospholipids. There is no...
Ferroptosis is a type of regulated cell death driven by the iron-dependent accumulation of oxidized polyunsaturated fatty acid-containing phospholipids. There is no reliable way to selectively stain ferroptotic cells in tissue sections to characterize the extent of ferroptosis in animal models or patient samples. We address this gap by immunizing mice with membranes from lymphoma cells treated with the ferroptosis inducer piperazine erastin and screening ∼4,750 of the resulting monoclonal antibodies generated for their ability to selectively detect cells undergoing ferroptosis. We find that one antibody, 3F3 ferroptotic membrane antibody (3F3-FMA), is effective as a selective ferroptosis-staining reagent. The antigen of 3F3-FMA is identified as the human transferrin receptor 1 protein (TfR1). We validate this finding with several additional anti-TfR1 antibodies and compare them to other potential ferroptosis-detecting reagents. We find that anti-TfR1 and anti-malondialdehyde adduct antibodies are effective at staining ferroptotic tumor cells in multiple cell culture and tissue contexts.
Topics: Animals; Antibodies, Monoclonal; Antigens; Biomarkers; Cell Line; Cell Line, Tumor; Cell Membrane; Ferroptosis; Golgi Apparatus; Humans; Injections; Mice; Piperazine; Piperazines; Receptors, Transferrin; Xenograft Model Antitumor Assays
PubMed: 32160546
DOI: 10.1016/j.celrep.2020.02.049 -
Cell Death & Disease Oct 2019Ferroptosis is a novel form of programmed cell death in which the accumulation of intracellular iron promotes lipid peroxidation, leading to cell death. Recently, the...
Ferroptosis is a novel form of programmed cell death in which the accumulation of intracellular iron promotes lipid peroxidation, leading to cell death. Recently, the induction of autophagy has been suggested during ferroptosis. However, this relationship between autophagy and ferroptosis is still controversial and the autophagy-inducing mediator remains unknown. In this study, we confirmed that autophagy is indeed induced by the ferroptosis inducer erastin. Furthermore, we show that autophagy leads to iron-dependent ferroptosis by degradation of ferritin and induction of transferrin receptor 1 (TfR1) expression, using wild-type and autophagy-deficient cells, BECN1 and LC3B. Consistently, autophagy deficiency caused depletion of intracellular iron and reduced lipid peroxidation, resulting in cell survival during erastin-induced ferroptosis. We further identified that autophagy was triggered by erastin-induced reactive oxygen species (ROS) in ferroptosis. These data provide evidence that ROS-induced autophagy is a key regulator of ferritin degradation and TfR1 expression during ferroptosis. Our study thus contributes toward our understanding of the ferroptotic processes and also helps resolve some of the controversies associated with this phenomenon.
Topics: Antigens, CD; Apoptosis; Autophagy; Beclin-1; Cytoplasm; Ferroptosis; Humans; Iron; Lipid Peroxidation; Microtubule-Associated Proteins; Piperazines; Reactive Oxygen Species; Receptors, Transferrin
PubMed: 31659150
DOI: 10.1038/s41419-019-2064-5 -
Nature Aug 2019Ferroptosis, a cell death process driven by cellular metabolism and iron-dependent lipid peroxidation, has been implicated in diseases such as ischaemic organ damage and...
Ferroptosis, a cell death process driven by cellular metabolism and iron-dependent lipid peroxidation, has been implicated in diseases such as ischaemic organ damage and cancer. The enzyme glutathione peroxidase 4 (GPX4) is a central regulator of ferroptosis, and protects cells by neutralizing lipid peroxides, which are by-products of cellular metabolism. The direct inhibition of GPX4, or indirect inhibition by depletion of its substrate glutathione or the building blocks of glutathione (such as cysteine), can trigger ferroptosis. Ferroptosis contributes to the antitumour function of several tumour suppressors such as p53, BAP1 and fumarase. Counterintuitively, mesenchymal cancer cells-which are prone to metastasis, and often resistant to various treatments-are highly susceptible to ferroptosis. Here we show that ferroptosis can be regulated non-cell-autonomously by cadherin-mediated intercellular interactions. In epithelial cells, such interactions mediated by E-cadherin suppress ferroptosis by activating the intracellular NF2 (also known as merlin) and Hippo signalling pathway. Antagonizing this signalling axis allows the proto-oncogenic transcriptional co-activator YAP to promote ferroptosis by upregulating several ferroptosis modulators, including ACSL4 and TFRC. This finding provides mechanistic insights into the observations that cancer cells with mesenchymal or metastatic property are highly sensitive to ferroptosis. Notably, a similar mechanism also modulates ferroptosis in some non-epithelial cells. Finally, genetic inactivation of the tumour suppressor NF2, a frequent tumorigenic event in mesothelioma, rendered cancer cells more sensitive to ferroptosis in an orthotopic mouse model of malignant mesothelioma. Our results demonstrate the role of intercellular interactions and intracellular NF2-YAP signalling in dictating ferroptotic death, and also suggest that malignant mutations in NF2-YAP signalling could predict the responsiveness of cancer cells to future ferroptosis-inducing therapies.
Topics: Adaptor Proteins, Signal Transducing; Animals; Antigens, CD; Cadherins; Cell Count; Coenzyme A Ligases; Epithelial Cells; Female; Ferroptosis; HCT116 Cells; Hippo Signaling Pathway; Humans; Mesothelioma; Mice; Mutation; Neurofibromin 2; Protein Serine-Threonine Kinases; Receptors, Transferrin; Signal Transduction; Transcription Factors; YAP-Signaling Proteins
PubMed: 31341276
DOI: 10.1038/s41586-019-1426-6 -
Nature Neuroscience Mar 2023Loss-of-function variants of TREM2 are associated with increased risk of Alzheimer's disease (AD), suggesting that activation of this innate immune receptor may be a...
Loss-of-function variants of TREM2 are associated with increased risk of Alzheimer's disease (AD), suggesting that activation of this innate immune receptor may be a useful therapeutic strategy. Here we describe a high-affinity human TREM2-activating antibody engineered with a monovalent transferrin receptor (TfR) binding site, termed antibody transport vehicle (ATV), to facilitate blood-brain barrier transcytosis. Upon peripheral delivery in mice, ATV:TREM2 showed improved brain biodistribution and enhanced signaling compared to a standard anti-TREM2 antibody. In human induced pluripotent stem cell (iPSC)-derived microglia, ATV:TREM2 induced proliferation and improved mitochondrial metabolism. Single-cell RNA sequencing and morphometry revealed that ATV:TREM2 shifted microglia to metabolically responsive states, which were distinct from those induced by amyloid pathology. In an AD mouse model, ATV:TREM2 boosted brain microglial activity and glucose metabolism. Thus, ATV:TREM2 represents a promising approach to improve microglial function and treat brain hypometabolism found in patients with AD.
Topics: Humans; Animals; Mice; Microglia; Blood-Brain Barrier; Alzheimer Disease; Tissue Distribution; Induced Pluripotent Stem Cells; Antibodies; Brain; Disease Models, Animal; Membrane Glycoproteins; Receptors, Immunologic
PubMed: 36635496
DOI: 10.1038/s41593-022-01240-0 -
Frontiers in Immunology 2021The transferrin receptor 1 (TfR1), also known as cluster of differentiation 71 (CD71), is a type II transmembrane glycoprotein that binds transferrin (Tf) and performs a... (Review)
Review
The transferrin receptor 1 (TfR1), also known as cluster of differentiation 71 (CD71), is a type II transmembrane glycoprotein that binds transferrin (Tf) and performs a critical role in cellular iron uptake through the interaction with iron-bound Tf. Iron is required for multiple cellular processes and is essential for DNA synthesis and, thus, cellular proliferation. Due to its central role in cancer cell pathology, malignant cells often overexpress TfR1 and this increased expression can be associated with poor prognosis in different types of cancer. The elevated levels of TfR1 expression on malignant cells, together with its extracellular accessibility, ability to internalize, and central role in cancer cell pathology make this receptor an attractive target for antibody-mediated therapy. The TfR1 can be targeted by antibodies for cancer therapy in two distinct ways: (1) indirectly through the use of antibodies conjugated to anti-cancer agents that are internalized by receptor-mediated endocytosis or (2) directly through the use of antibodies that disrupt the function of the receptor and/or induce Fc effector functions, such as antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), or complement-dependent cytotoxicity (CDC). Although TfR1 has been used extensively as a target for antibody-mediated cancer therapy over the years, interest continues to increase for both targeting the receptor for delivery purposes and for its use as direct anti-cancer agents. This review focuses on the developments in the use of antibodies targeting TfR1 as direct anti-tumor agents.
Topics: Animals; Antibody-Dependent Cell Cytotoxicity; Antigens, CD; Antineoplastic Agents, Immunological; Biological Transport; Biomarkers, Tumor; Cell Line, Tumor; Drug Evaluation, Preclinical; Gene Expression Regulation, Neoplastic; Humans; Iron; Molecular Targeted Therapy; Receptors, Transferrin; Signal Transduction; Xenograft Model Antitumor Assays
PubMed: 33815364
DOI: 10.3389/fimmu.2021.607692 -
Circulation Sep 2022Iron deficiency is common in heart failure and associated with worse outcomes. We examined the prevalence and consequences of iron deficiency in the DAPA-HF trial... (Randomized Controlled Trial)
Randomized Controlled Trial
BACKGROUND
Iron deficiency is common in heart failure and associated with worse outcomes. We examined the prevalence and consequences of iron deficiency in the DAPA-HF trial (Dapagliflozin and Prevention of Adverse-Outcomes in Heart Failure) and the effect of dapagliflozin on markers of iron metabolism. We also analyzed the effect of dapagliflozin on outcomes, according to iron status at baseline.
METHODS
Iron deficiency was defined as a ferritin level <100 ng/mL or a transferrin saturation <20% and a ferritin level 100 to 299 ng/mL. Additional biomarkers of iron metabolism, including soluble transferrin receptor, erythropoietin, and hepcidin were measured at baseline and 12 months after randomization. The primary outcome was a composite of worsening heart failure (hospitalization or urgent visit requiring intravenous therapy) or cardiovascular death.
RESULTS
Of the 4744 patients randomized in DAPA-HF, 3009 had ferritin and transferrin saturation measurements available at baseline, and 1314 of these participants (43.7%) were iron deficient. The rate of the primary outcome was higher in patients with iron deficiency (16.6 per 100 person-years) compared with those without (10.4 per 100 person-years; <0.0001). The effect of dapagliflozin on the primary outcome was consistent in iron-deficient compared with iron-replete patients (hazard ratio, 0.74 [95% CI, 0.58-0.92] versus 0.81 [95% CI, 0.63-1.03]; -interaction=0.59). Similar findings were observed for cardiovascular death, heart failure hospitalization, and all-cause mortality. Transferrin saturation, ferritin, and hepcidin were reduced and total iron-binding capacity and soluble transferrin receptor increased with dapagliflozin compared with placebo.
CONCLUSIONS
Iron deficiency was common in DAPA-HF and associated with worse outcomes. Dapagliflozin appeared to increase iron use but improved outcomes, irrespective of iron status at baseline.
REGISTRATION
URL: https://www.
CLINICALTRIALS
gov; Unique identifier: NCT03036124.
Topics: Benzhydryl Compounds; Biomarkers; Ferritins; Glucosides; Heart Failure; Hepcidins; Humans; Iron; Iron Deficiencies; Receptors, Erythropoietin; Receptors, Transferrin; Stroke Volume; Transferrins
PubMed: 35971840
DOI: 10.1161/CIRCULATIONAHA.122.060511 -
Science Immunology Jan 2023T cells in systemic lupus erythematosus (SLE) exhibit multiple metabolic abnormalities. Excess iron can impair mitochondria and may contribute to SLE. To gain insights...
T cells in systemic lupus erythematosus (SLE) exhibit multiple metabolic abnormalities. Excess iron can impair mitochondria and may contribute to SLE. To gain insights into this potential role of iron in SLE, we performed a CRISPR screen of iron handling genes on T cells. Transferrin receptor (CD71) was identified as differentially critical for T1 and inhibitory for induced regulatory T cells (iT). Activated T cells induced CD71 and iron uptake, which was exaggerated in SLE-prone T cells. Cell surface CD71 was enhanced in SLE-prone T cells by increased endosomal recycling. Blocking CD71 reduced intracellular iron and mTORC1 signaling, which inhibited T1 and T17 cells yet enhanced iT. In vivo treatment reduced kidney pathology and increased CD4 T cell production of IL-10 in SLE-prone mice. Disease severity correlated with CD71 expression on T17 cells from patients with SLE, and blocking CD71 in vitro enhanced IL-10 secretion. T cell iron uptake via CD71 thus contributes to T cell dysfunction and can be targeted to limit SLE-associated pathology.
Topics: Animals; Mice; Interleukin-10; Lupus Erythematosus, Systemic; Receptors, Transferrin; T-Lymphocytes, Regulatory; Humans
PubMed: 36638190
DOI: 10.1126/sciimmunol.abq0178 -
Cell Sep 2021GRN mutations cause frontotemporal dementia (GRN-FTD) due to deficiency in progranulin (PGRN), a lysosomal and secreted protein with unclear function. Here, we found...
GRN mutations cause frontotemporal dementia (GRN-FTD) due to deficiency in progranulin (PGRN), a lysosomal and secreted protein with unclear function. Here, we found that Grn mice exhibit a global deficiency in bis(monoacylglycero)phosphate (BMP), an endolysosomal phospholipid we identified as a pH-dependent PGRN interactor as well as a redox-sensitive enhancer of lysosomal proteolysis and lipolysis. Grn brains also showed an age-dependent, secondary storage of glucocerebrosidase substrate glucosylsphingosine. We investigated a protein replacement strategy by engineering protein transport vehicle (PTV):PGRN-a recombinant protein linking PGRN to a modified Fc domain that binds human transferrin receptor for enhanced CNS biodistribution. PTV:PGRN rescued various Grn phenotypes in primary murine macrophages and human iPSC-derived microglia, including oxidative stress, lysosomal dysfunction, and endomembrane damage. Peripherally delivered PTV:PGRN corrected levels of BMP, glucosylsphingosine, and disease pathology in Grn CNS, including microgliosis, lipofuscinosis, and neuronal damage. PTV:PGRN thus represents a potential biotherapeutic for GRN-FTD.
Topics: Animals; Biological Products; Bone Morphogenetic Proteins; Brain; Endosomes; Female; Frontotemporal Dementia; Gliosis; Humans; Induced Pluripotent Stem Cells; Inflammation; Lipid Metabolism; Lipofuscin; Lysosomal Storage Diseases; Lysosomes; Macrophages; Male; Membrane Glycoproteins; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microglia; Nerve Degeneration; Phenotype; Progranulins; Receptors, Immunologic; Receptors, Transferrin; Tissue Distribution
PubMed: 34450028
DOI: 10.1016/j.cell.2021.08.002