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The American Journal of Clinical... Dec 2017Biochemical assessment of iron status relies on serum-based indicators, such as serum ferritin (SF), transferrin saturation, and soluble transferrin receptor (sTfR), as... (Review)
Review
Biochemical assessment of iron status relies on serum-based indicators, such as serum ferritin (SF), transferrin saturation, and soluble transferrin receptor (sTfR), as well as erythrocyte protoporphyrin. These indicators present challenges for clinical practice and national nutrition surveys, and often iron status interpretation is based on the combination of several indicators. The diagnosis of iron deficiency (ID) through SF concentration, the most commonly used indicator, is complicated by concomitant inflammation. sTfR concentration is an indicator of functional ID that is not an acute-phase reactant, but challenges in its interpretation arise because of the lack of assay standardization, common reference ranges, and common cutoffs. It is unclear which indicators are best suited to assess excess iron status. The value of hepcidin, non-transferrin-bound iron, and reticulocyte indexes is being explored in research settings. Serum-based indicators are generally measured on fully automated clinical analyzers available in most hospitals. Although international reference materials have been available for years, the standardization of immunoassays is complicated by the heterogeneity of antibodies used and the absence of physicochemical reference methods to establish "true" concentrations. From 1988 to 2006, the assessment of iron status in NHANES was based on the multi-indicator ferritin model. However, the model did not indicate the severity of ID and produced categorical estimates. More recently, iron status assessment in NHANES has used the total body iron stores (TBI) model, in which the log ratio of sTfR to SF is assessed. Together, sTfR and SF concentrations cover the full range of iron status. The TBI model better predicts the absence of bone marrow iron than SF concentration alone, and TBI can be analyzed as a continuous variable. Additional consideration of methodologies, interpretation of indicators, and analytic standardization is important for further improvements in iron status assessment.
Topics: Biomarkers; Ferritins; Humans; Iron; Nutrition Assessment; Nutrition Surveys; Nutritional Status; Receptors, Transferrin
PubMed: 29070545
DOI: 10.3945/ajcn.117.155887 -
Fluids and Barriers of the CNS Nov 2023Here, we report an experimental setup to benchmark different receptors for targeted therapeutic antibody delivery at the blood-brain barrier. We used brain capillary...
Here, we report an experimental setup to benchmark different receptors for targeted therapeutic antibody delivery at the blood-brain barrier. We used brain capillary endothelial-like cells derived from induced pluripotent stem cells (hiPSC-BECs) as a model system and compared them to colon epithelial Caco-2 cells. This approach helped to identify favourable receptors for transport into the cell layer itself or for directing transport for transcytosis across the cell layer. The sorting receptors transferrin receptor and sortilin were shown to be efficient as antibody cargo receptors for intracellular delivery to the cell layer. In contrast, the cell surface receptors CD133 and podocalyxin were identified as static and inefficient receptors for delivering cargo antibodies. Similar to in vivo studies, the hiPSC-BECs maintained detectable transcytotic transport via transferrin receptor, while transcytosis was restricted using sortilin as a cargo receptor. Based on these findings, we propose the application of sortilin as a cargo receptor for delivering therapeutic antibodies into the brain microvascular endothelium.
Topics: Humans; Blood-Brain Barrier; Caco-2 Cells; Transcytosis; Biological Transport; Brain; Receptors, Transferrin
PubMed: 37932749
DOI: 10.1186/s12987-023-00480-x -
Journal of Neurochemistry Nov 2020Previous work by our group has shown the pro-differentiating effects of apotransferrin (aTf) on oligodendroglial cells in vivo and in vitro. Further studies showed the...
Previous work by our group has shown the pro-differentiating effects of apotransferrin (aTf) on oligodendroglial cells in vivo and in vitro. Further studies showed the remyelinating effect of aTf in animal demyelination models such as hypoxia/ischemia, where the intranasal administration of human aTf provided brain neuroprotection and reduced white matter damage, neuronal loss, and astrogliosis in different brain regions. These data led us to search for a less invasive and controlled technique to deliver aTf to the CNS. To such end, we isolated extracellular vesicles (EVs) from human and mouse plasma and different neuron and glia conditioned media and characterized them based on their quality, quantity, identity, and structural integrity by western blot, dynamic light scattering, and scanning electron microscopy. All sources yielded highly pure vesicles whose size and structures were in keeping with previous literary evidence. Given that, remarkably, EVs from all sources analyzed contained Tf receptor 1 (TfR1) in their composition, we employed two passive cargo-loading strategies which rendered successful EV loading with aTf, specifically through binding to TfR1. These results unveil EVs as potential nanovehicles of aTf to be delivered into the CNS parenchyma, and pave the way for further studies into their possible clinical application in the treatment of demyelinating diseases.
Topics: Adult; Animals; Apoproteins; Astrocytes; Cell Line, Transformed; Cell Line, Tumor; Cells, Cultured; Extracellular Vesicles; Female; Humans; Male; Mice; Nanoparticles; Rats; Rats, Wistar; Receptors, Transferrin; Transferrin
PubMed: 32248519
DOI: 10.1111/jnc.15019 -
Drug Discovery Today. Technologies Jun 2016Delivery of large molecule drugs across the blood brain barrier is increasingly being seen as an achievable goal. Several technologies have been described where... (Review)
Review
Delivery of large molecule drugs across the blood brain barrier is increasingly being seen as an achievable goal. Several technologies have been described where following peripheral administration the molecules can be detected in the brain. Foremost amongst these technologies are antibodies against the transferrin receptor. Following a burst of publications in the very early twenty first century, excitement seemed to wane as contrary data started to emerge. Over the last few years antibodies against transferrin receptor have again started to raise hopes of successful drug delivery to the central nervous system, as protein engineering techniques have allowed a more detailed understanding of the antibody properties necessary for successful transport across the blood brain barrier.
Topics: Animals; Antibodies; Blood-Brain Barrier; Drug Delivery Systems; Humans; Pharmaceutical Preparations; Receptors, Transferrin
PubMed: 27986223
DOI: 10.1016/j.ddtec.2016.07.009 -
Proceedings of the National Academy of... Apr 2021The de novo design of polar protein-protein interactions is challenging because of the thermodynamic cost of stripping water away from the polar groups. Here, we...
The de novo design of polar protein-protein interactions is challenging because of the thermodynamic cost of stripping water away from the polar groups. Here, we describe a general approach for designing proteins which complement exposed polar backbone groups at the edge of beta sheets with geometrically matched beta strands. We used this approach to computationally design small proteins that bind to an exposed beta sheet on the human transferrin receptor (hTfR), which shuttles interacting proteins across the blood-brain barrier (BBB), opening up avenues for drug delivery into the brain. We describe a design which binds hTfR with a 20 nM , is hyperstable, and crosses an in vitro microfluidic organ-on-a-chip model of the human BBB. Our design approach provides a general strategy for creating binders to protein targets with exposed surface beta edge strands.
Topics: Blood-Brain Barrier; Brain; Drug Delivery Systems; Humans; Protein Engineering; Proteins; Receptors, Transferrin; Transferrin
PubMed: 33879614
DOI: 10.1073/pnas.2021569118 -
Proceedings of the National Academy of... Oct 2019Canine parvovirus (CPV) is an important pathogen causing severe diseases in dogs, including acute hemorrhagic enteritis, myocarditis, and cerebellar disease....
Canine parvovirus (CPV) is an important pathogen causing severe diseases in dogs, including acute hemorrhagic enteritis, myocarditis, and cerebellar disease. Cross-species transmission of CPV occurs as a result of mutations on the viral capsid surface that alter the species-specific binding to the host receptor, transferrin receptor type-1 (TfR). The interaction between CPV and TfR has been extensively studied, and previous analyses have suggested that the CPV-TfR complex is asymmetric. To enhance the understanding of the underlying molecular mechanisms, we determined the CPV-TfR interaction using cryo-electron microscopy to solve the icosahedral (3.0-Å resolution) and asymmetric (5.0-Å resolution) complex structures. Structural analyses revealed conformational variations of the TfR molecules relative to the binding site, which translated into dynamic molecular interactions between CPV and TfR. The precise footprint of the receptor on the virus capsid was identified, along with the identity of the amino acid residues in the virus-receptor interface. Our "rock-and-roll" model provides an explanation for previous findings and gives insights into species jumping and the variation in host ranges associated with new pandemics in dogs.
Topics: Animals; Capsid; Cats; Cryoelectron Microscopy; Dogs; Parvovirus, Canine; Protein Conformation; Receptors, Transferrin; Receptors, Virus; Species Specificity; Virion
PubMed: 31548398
DOI: 10.1073/pnas.1904918116 -
American Journal of Human Genetics Feb 2018Neurodegeneration with brain iron accumulation (NBIA) is a genetically heterogeneous condition characterized by progressive dystonia with iron accumulation in the basal...
Neurodegeneration with brain iron accumulation (NBIA) is a genetically heterogeneous condition characterized by progressive dystonia with iron accumulation in the basal ganglia. How NBIA-associated mutations trigger iron overload remains poorly understood. After studying fibroblast cell lines from subjects carrying both known and unreported biallelic mutations in CRAT and REPS1, we ascribe iron overload to the abnormal recycling of transferrin receptor (TfR1) and the reduction of TfR1 palmitoylation in NBIA. Moreover, we describe palmitoylation as a hitherto unreported level of post-translational TfR1 regulation. A widely used antimalarial agent, artesunate, rescued abnormal TfR1 palmitoylation in cultured fibroblasts of NBIA subjects. These observations suggest therapeutic strategies aimed at targeting impaired TfR1 recycling and palmitoylation in NBIA.
Topics: Amino Acid Sequence; Brain; Calcium-Binding Proteins; Carrier Proteins; Endocytosis; Fibroblasts; HEK293 Cells; HeLa Cells; Homeostasis; Humans; Iron; Lipoylation; Mutation; Nerve Degeneration; Receptors, Transferrin; Transferrin
PubMed: 29395073
DOI: 10.1016/j.ajhg.2018.01.003 -
The EMBO Journal Jul 2013EMBO J 32 15, 2125–2139 doi:; DOI: 10.1038/emboj.2013.130; published online June 07 2013 Protein sorting pathways control correct delivery of membrane proteins to...
EMBO J 32 15, 2125–2139 doi:; DOI: 10.1038/emboj.2013.130; published online June 07 2013 Protein sorting pathways control correct delivery of membrane proteins to specific compartments of the plasma membrane and are required to maintain the physiological functions in all epithelia. Most clathrin-dependent cargoes require the adaptor protein complexes AP-1A and AP-1B for proper sorting to the basolateral plasma membrane. In this issue of , Perez Bay et al (2013) shed light on the mechanism of basal-to-apical protein transport, or transcytosis, of the transferrin receptor in natively AP-1B-deficient epithelia. In AP-1B-deficient epithelia, the transferrin receptor transcytoses through the apical recycling endosome, and requires Rab11. Furthermore, they characterize a novel and specific role for the endosomal microtubule motor Kinesin KIF16B in transferrin receptor apical transport. These findings constitute the first characterization of a specific microtubule motor involved in basal-to-apical transcytosis in epithelia.
Topics: Adaptor Protein Complex 1; Animals; Endosomes; Epithelial Cells; Humans; Kinesins; Microtubules; Receptors, Transferrin; Transcytosis
PubMed: 23812008
DOI: 10.1038/emboj.2013.153 -
Cell Communication and Signaling : CCS Oct 2018Transmissible gastroenteritis virus (TGEV), the etiologic agent of transmissible gastroenteritis, infects swine of all ages causing vomiting and diarrhea, in newborn...
BACKGROUND
Transmissible gastroenteritis virus (TGEV), the etiologic agent of transmissible gastroenteritis, infects swine of all ages causing vomiting and diarrhea, in newborn piglets the mortality rate is near 100%. Intestinal epithelial cells are the primary target cells of TGEV. Transferrin receptor 1 (TfR1), which is highly expressed in piglets with anemia, may play a role in TGEV infection. However, the underlying mechanism of TGEV invasion remains largely unknown.
RESULTS
Our study investigated the possibility that TfR1 can serve as a receptor for TGEV infection and enables the invasion and replication of TGEV. We observed that TGEV infection promoted TfR1 internalization, clustering, and co-localization with TfR1 early in infection, while TfR1 expression was significantly down-regulated as TGEV infection proceeded. TGEV infection and replication were inhibited by occluding TfR1 with antibodies or by decreasing TfR1 expression. TGEV infection increased in TGEV-susceptible ST or IPEC-J2 cell lines and TGEV-resistant Caco-2 cells when porcine TfR1 was over-expressed. Finally, we found that the TGEV S1 protein interacts with the extracellular region of TfR1, and that pre-incubating TGEV with a protein fragment containing the extracellular region of TfR1 blocked viral infection.
CONCLUSIONS
Our results support the hypothesis that TfR1 is an additional receptor for TGEV and assists TGEV invasion and replication.
Topics: Animals; Caco-2 Cells; Endocytosis; Extracellular Space; Humans; Intestinal Mucosa; Protein Transport; Receptors, Transferrin; Swine; Transmissible gastroenteritis virus; Viral Tropism; Virion; Virus Internalization
PubMed: 30342530
DOI: 10.1186/s12964-018-0283-5 -
BMC Biology Aug 2022T cell activation leads to increased expression of the receptor for the iron transporter transferrin (TfR) to provide iron required for the cell differentiation and...
BACKGROUND
T cell activation leads to increased expression of the receptor for the iron transporter transferrin (TfR) to provide iron required for the cell differentiation and clonal expansion that takes place during the days after encounter with a cognate antigen. However, T cells mobilise TfR to their surface within minutes after activation, although the reason and mechanism driving this process remain unclear.
RESULTS
Here we show that T cells transiently increase endocytic uptake and recycling of TfR upon activation, thereby boosting their capacity to import iron. We demonstrate that increased TfR recycling is powered by a fast endocytic sorting pathway relying on the membrane proteins flotillins, Rab5- and Rab11a-positive endosomes. Our data further reveal that iron import is required for a non-canonical signalling pathway involving the kinases Zap70 and PAK, which controls adhesion of the integrin LFA-1 and eventually leads to conjugation with antigen-presenting cells.
CONCLUSIONS
Altogether, our data suggest that T cells boost their iron importing capacity immediately upon activation to promote adhesion to antigen-presenting cells.
Topics: Endocytosis; Endosomes; Iron; Receptors, Transferrin; T-Lymphocytes; Transferrin
PubMed: 36002835
DOI: 10.1186/s12915-022-01386-0