Alpha haemoglobin-stabilising protein concentration in the red blood cells of patients with sickle cell anaemia with and without hydroxycarbamide treatment.

Alpha haemoglobin-stabilising protein (AHSP) is a key chaperone synthesised in red blood cell (RBC) precursors. Many studies have reported AHSP as a potential biomarker of various diseases. AHSP gene expression has been studied in detail, but little is known about AHSP protein levels in RBCs.

Ex Vivo Activation of Red Blood Cell Senescence by Plasma from Sickle-Cell Disease Patients: Correlation between Markers and Adhesion Consequences during Acute Disease Events.

Background: Blood transfusion remains a key treatment for managing occlusive episodes and painful crises in sickle-cell disease (SCD). In that clinical context, red blood cells (RBCs) from donors and transfused to patients, may be affected by plasma components in the recipients' blood. Senescence lesion markers appear on the red cells after transfusion, shortening the RBC lifespan in circulation.

Red blood cells free α-haemoglobin pool: a biomarker to monitor the β-thalassemia intermedia variability. The ALPHAPOOL study.

The severity of β-thalassaemia (β-thal) intermedia is mainly correlated to the degree of imbalanced α/non α-globin chain synthesis. The phenotypic diversity of β-thal depends on this imbalance and reflects all possible combinations of α- and β-globin genotypes, levels of fetal haemoglobin (HbF) and co-inheritance of other modulating factors. This study aimed to demonstrate the validity of a new surrogate of α/non α-globin biosynthetic ratio by measuring the soluble α-Hb pool in lysed red blood cells.

Role of α-globin H helix in the building of tetrameric human hemoglobin: interaction with α-hemoglobin stabilizing protein (AHSP) and heme molecule.

Alpha-Hemoglobin Stabilizing Protein (AHSP) binds to α-hemoglobin (α-Hb) or α-globin and maintains it in a soluble state until its association with the β-Hb chain partner to form Hb tetramers. AHSP specifically recognizes the G and H helices of α-Hb. To investigate the degree of interaction of the various regions of the α-globin H helix with AHSP, this interface was studied by stepwise elimination of regions of the α-globin H helix: five truncated α-Hbs α-Hb1-138, α-Hb1-134, α-Hb1-126, α-Hb1-123, α-Hb1-117 were co-expressed with AHSP as two glutathione-S-transferase (GST) fusion proteins.

Dynamics of α-Hb chain binding to its chaperone AHSP depends on heme coordination and redox state.

Background: AHSP is an erythroid molecular chaperone of the α-hemoglobin chains (α-Hb). Upon AHSP binding, native ferric α-Hb undergoes an unprecedented structural rearrangement at the heme site giving rise to a 6th coordination bond with His(E7).

Methods: Recombinant AHSP, WT α-Hb:AHSP and α-Hb(HE7Q):AHSP complexes were expressed in Escherichia coli.

Interaction of haptoglobin with hemoglobin octamers based on the mutation Asn78Cys or Gly83Cys.

Octameric hemoglobins have been developed by the introduction of surface cysteines in either the alpha or beta chain. Originally designed as a blood substitute, we report here the structure and ligand binding function; in addition the interaction with haptoglobin was studied. The recombinant Hbs (rHbs) with mutations alpha Asn78Cys or beta Gly83Cys spontaneously form octamers under conditions where the cysteines are oxidized.

α-Hemoglobin stabilizing protein: a modulating factor in thalassemias?

α-Hemoglobin stabilizing protein (AHSP) is a small protein of 102 residues induced by GATA-1, Oct-1- and EKLF. It is synthesized at a high level in the red blood cell precursors and acts as a chaperone protecting the α-hemoglobin (α-Hb) chains against precipitation. α-Hemoglobin stabilizing protein forms a heterodimer complex with α-Hb, then displaying modified oxygen binding kinetics.

Evaluation of the free α-hemoglobin pool in red blood cells: a new test providing a scale of β-thalassemia severity.

β-Thalassemias are characterized by an imbalance of globin chains with an excess of α-chains which precipitates in erythroid precursors and red blood cells (RBCs) leading to inefficient erythropoiesis. The severity of the disease correlates with the amount of unpaired α-chains.Our goal was to develop a simple test for evaluation of the free α-hemoglobin pool present in RBC lysates.

Alpha-hemoglobin stabilizing protein (AHSP), a kinetic scheme of the action of a human mutant, AHSPV56G.

A kinetic analysis has been made of the interaction of alpha-Hb chains with a mutant alpha-hemoglobin stabilizing protein, AHSP(V56G), which is the first case of an AHSP mutation associated with clinical symptoms of mild thalassemia syndrome. The chaperone AHSP is thought to protect nascent alpha chains until final binding to the partner beta-Hb. Rather than protecting alpha chains, the mutant chaperone is partially unfolded but recovers its secondary structure via interaction with alpha-Hb.

The alpha-hemoglobin stabilizing protein and expression of unstable alpha-Hb variants.

Objectives: To determine the role of the alpha-hemoglobin stabilizing protein (AHSP) in the clinical expression of alpha-hemoglobin (alpha-Hb) variants described as unstable, ten alpha chain variants have been studied with their chaperone. AHSP specifically binds free alpha-Hb to form a soluble heterodimer until it is replaced by the beta-Hb partner. In this way, AHSP prevents the precipitation of free alpha chains which might damage the membrane of erythrocyte.

Construction of a new polycistronic vector for over-expression and rapid purification of human hemoglobin.

To facilitate the study of the structure-function relationship of human hemoglobin (Hb A), we have developed a new hemoglobin expression vector, pGEX6P-alpha-[SD]-beta. This vector allows the co-expression of alpha-Hb as a fusion protein with Glutathione S-Transferase (GST-alpha-Hb) and beta-Hb with an additional methionine at the N-terminal extremity (rbeta-Hb). These proteins were solubilized as GST-alpha-Hb/rbeta-Hb complex form and purified in one step by affinity chromatography on immobilized glutathione.

Octamers and nanoparticles as hemoglobin based blood substitutes.

Progress in developing a blood substitute is aided by new biotechnologies and a better understanding of the circulatory system. For Hb based solutions, there is still a debate over the best set of fundamental parameters concerning the oxygen affinity which is correlated with the oxidation rate, the cooperativity, the transporter size, and of course the final source of material. Genetic engineering methods have helped discover novel globins, but not yet the quantity necessary for the high demand of blood transfusions.