Gene Ontology annotation through association of InterPro records with GO terms.
Annotation inferences using phylogenetic trees
Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping
Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara.
The human plasma proteome: a nonredundant list developed by combination of four separate sources.
Human colostrum: identification of minor proteins in the aqueous phase by proteomics.
Large-scale proteomics and phosphoproteomics of urinary exosomes.
Hemoglobin and its scavenger protein haptoglobin associate with apoA-1-containing particles and influence the inflammatory properties and function of high density lipoprotein.
Kinetics and specificity of feline leukemia virus subgroup C receptor (FLVCR) export function and its dependence on hemopexin.
Proteomic analysis of microvesicles from plasma of healthy donors reveals high individual variability.
In-depth proteomic analyses of exosomes isolated from expressed prostatic secretions in urine.
Architecture of the human interactome defines protein communities and disease networks.
Characterization of the Extracellular Matrix of Normal and Diseased Tissues Using Proteomics.
Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
Complete amino acid sequence of human hemopexin, the heme-binding protein of serum.
Scavenging of heme from plasma
Ferriheme is transferred from Methemoglobin to Hemopexin
Ferriheme is transferred from Albumin to Hemopexin
LRP1 (CD91) binds Hemopexin:heme
LRP1:Hemopexin:heme is endocytosed
Deep research on HPX function
Falcon deep research report on human HPX (hemopexin)
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HPX is a ~60 kDa plasma glycoprotein and the highest-affinity heme-binding protein in plasma, present in plasma, CSF, and lymph; stoichiometry is 1:1 at low heme and ≥2:1 (heme:HPX) at higher heme; plasma concentration is ~0.4–1.5 mg/mL.
"Hemopexin is described as a **plasma glycoprotein (~60 kDa)** and the **highest-affinity heme-binding protein in plasma**, functioning as a systemic heme scavenger during hemolysis."
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Beyond CD91/LRP1, HPX uptake involves transferrin receptor 1 (TfR1) in Rab5-positive early endosomes and proceeds even in LRP1-/- cells, indicating multiple endocytic routes. LRP1 binds HPX with Kd ≈ 4 nM.
"HPX trafficked with transferrin and transferrin receptor 1 (TfR1) in Rab5-positive early endosomes, consistent with clathrin-mediated endocytosis routes used by iron transport machinery; TfR2 co-localization suggests potential contribution to liver targeting."
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Heme delivered by HPX initiates a cytoprotective program including HMOX1 (HO-1) induction, ferritin induction, and downregulation of transferrin receptor; HPX participates in heme-responsive homeostatic programming rather than simple neutralization.
"Mechanistic literature frames HPX not only as a heme sink but as a **ligand delivery system** that initiates regulated cellular responses. Heme–HPX endocytosis is linked to HO-1 induction and coordinated iron handling (ferritin induction, transferrin receptor downregulation)"
Double-edged functions of hemopexin in hematological related diseases: from basic mechanisms to clinical application.
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HPX is a 60 kDa plasma glycoprotein with exceptional heme binding affinity, 1:1 at low heme and ≥2:1 (heme:HPX) at higher concentrations; circulates at 0.5–1.5 mg/mL; primarily produced by liver but also found in nervous system, skeletal muscle, retina, and kidney.
"It is a plasma glycoprotein composed of a single 60-kDa peptide chain, known for its exceptional binding affinity to heme. HPX exhibits a 1:1 binding ratio with heme at low concentrations and at least a 2:1 ratio (heme: hemopexin) at higher heme concentrations."
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HPX is a second-line defense after haptoglobin depletion; heme-HPX is phagocytosed by macrophages via CD91, and heme is metabolized to bilirubin, CO, and iron by Bach1/Nrf2-induced HO-1; iron is stored in ferritin or exported via ferroportin.
"Mechanistically, the heme-HPX complex is phagocytosed by macrophages through CD91 and subsequently broken down inside the cells. Heme undergoes metabolism, forming bilirubin, carbon monoxide, and iron, facilitated by heme/Bach1/Nrf2-induced heme oxygenase-1 (HO-1)."
Tracking hemopexin intracellularly and defining hemopexin protein "interactomes" in human immune and liver cell models.
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LRP1 is a high-affinity HPX-binding protein (Kd ~4 nM); however, heme-HPX endocytosis also occurs in LRP1-/- cells, and HPX co-traffics with transferrin/TfR1 in Rab5-positive early endosomes, implicating TfR1 (and possibly TfR2) in heme-HPX endocytosis.
"shown by surface plasmon resonance to be a high-affinity HPX-binding protein, Kd 4 nM (Hvidberg et al., 2005)"
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Heme-HPX binding initiates a cytoprotective program including HMOX1 induction and ferritin-mediated iron storage.
"In cultured cells, heme–HPX binding and heme delivery initiate a "cytoprotective" program of events (Montecinos et al., 2019), including the induction of the heme degrading enzyme heme oxygenase (HMOX1)."
What Is Next in This "Age" of Heme-Driven Pathology and Protection by Hemopexin? An Update and Links with Iron.