Disease relevance of ERAF

• AHSP has been proposed as a candidate gene in some Heinz body hemolytic anemias and as a modifier gene in the beta-thalassemia syndromes [1].
• It remains to be seen if any association between AHSP and clinical severity is present in other population groups with a high frequency of beta thalassemia [2].
• Using gene mapping, direct genomic sequencing, and extended haplotype analysis, we found no mutation or specific association between haplotypes of AHSP and disease severity in these patients, suggesting that AHSP is not a disease modifier in Hb E-beta thalassemia [2].
• We also propose that absence of AHSP in EKLF-null red cells exacerbates the toxicity of free alpha-globin chains, which exist because of the defect in beta-globin gene activation [3].
• However, the role of EDRF-mediated pulmonary-artery relaxation in chronic hypoxic lung disease is unknown [4].

Psychiatry related information on ERAF

• EDRF transcripts and diagnosis of variant Creutzfeldt-Jakob disease [5].
• OBJECTIVES: to provide data and detect possible differences in self-assessment of appetite, hunger feelings and sensory perception in different health group of elderly using the Appetite, Hunger feelings and Sensory Perception (AHSP) questionnaire [6].

High impact information on ERAF

• Inhibition of EDRF synthesis by treatment with NG-monomethyl-L-arginine (10(-4) M) eliminated this difference, increasing the tension in the rings from the controls (P less than 0.01) but not in those from the patients with chronic lung disease [4].
• Endothelial cells release endothelium-derived relaxing factor (EDRF) in a variety of vascular beds, including the pulmonary circulation [4].
• We studied endothelium-dependent relaxation mediated by EDRF in vitro in pulmonary arteries that had been obtained from 22 patients undergoing heart-lung transplantation for end-stage chronic obstructive lung disease [4].
• Hence, AHSP is required for normal erythropoiesis, probably acting to block the deleterious effects of free alpha-haemoglobin precipitation [7].
• Accordingly, AHSP gene dosage is predicted to modulate pathological states of alpha-haemoglobin excess, such as beta-thalassaemia [7].

Chemical compound and disease context of ERAF

• Therefore, we investigated whether acetylcholine releases EDRF in humans in vivo and, if so, whether the response altered in essential hypertension [8].
• Nitroglycerin (NTG), frequently utilized in the management of unstable angina pectoris and acute myocardial infarction, undergoes bioconversion, via a sulfhydryl-dependent process, to nitric oxide, which is identical or closely related to EDRF [9].
• The release of EDRF from the endothelium can be mediated by both pertussis toxin-sensitive (alpha 2-adrenoceptor activation, serotonin, aggregating platelets, leukotrienes) and insensitive (adenosine diphosphate (ADP), bradykinin) G proteins [10].
• The antiaggregatory effect of EDRF is synergistic with prostacyclin, so their combined release may represent a physiological mechanism aimed at preventing thrombus formation [11].
• Hence, impairment of EDRF release or function could contribute to the reduced placental blood flow observed in various disease states associated with increased thromboxane A2 production such as pre-eclampsia [12].

Biological context of ERAF

• Alpha-hemoglobin-stabilizing protein (AHSP) is an erythroid protein that binds and stabilizes alpha-hemoglobin during normal erythropoiesis and in pathological states of alpha-hemoglobin excess [1].
• The AHSP promoter is an excellent candidate region for mutations associated with decreased AHSP gene expression [1].
• In transgenic mice, a reporter gene directed by a minimal human AHSP promoter was expressed in bone marrow, spleen, and reticulocytes, but not in nonerythroid tissues [1].
• Biophysical characterization of the alpha-globin binding protein alpha-hemoglobin stabilizing protein [13].
• The CO rebinding kinetics of the AHSP/alpha-Hb(42mutant) complexes were similar to those previously obtained with the AHSP/alpha-Hb(WT) complex, which shows a modified rate that is intermediate to the classical Hb allosteric states [14].

Anatomical context of ERAF

• Folding in the endoplasmic reticulum (ER) must couple protein-synthesis pathways operating outside of the compartment with ER-assisted folding (ERAF) pathways in the lumen [15].
• The alpha-hemoglobin-stabilizing protein (AHSP), a small protein of 102 amino acids, is synthesized in red blood cell precursors [16].
• Because AHSP might act as a chaperone to prevent the harmful aggregation of alpha-globin during normal erythroid cell development and in diseases of globin chain imbalance, it is important to characterize the biochemical properties of the AHSP.alpha-globin complex [13].
• He then recounts how an accidental finding in an experiment in 1978 on preparations of rabbit aorta eventually led to the discovery of endothelium dependent relaxation and the endothelium-derived relaxing factor (EDRF); and how additional findings led him to propose in 1986 that EDRF is nitric oxide [17].
• The discovery of endothelium-derived relaxing factor (EDRF) and its importance in the identification of nitric oxide (NO) originated with studies using rabbit aorta to examine drug-receptor interactions in vascular smooth muscle [18].

Associations of ERAF with chemical compounds

• In vitro the binding of AHSP to ferrous alpha-Hb accelerates oxidation of the heme iron in alpha-Hb, but the complex is more resistant to protein unfolding [14].
• Results obtained with recombinant Groene Hart alpha-Hb and Diamant alpha-Hb, in which proline 119 is replaced by a serine and a leucine, respectively, showed clearly an impaired interaction with AHSP [14].
• Bradykinin caused concentration-dependent release of NO from the cells in amounts sufficient to account for the biological activity of EDRF [19].
• Smooth muscle relaxation by acetylcholine and a number of other agonists was found to be dependent on the presence of endothelial cells, which, when stimulated by the agonist, released a diffusable, very labile, nonprostanoid substance, termed EDRF, that acted on vascular smooth muscle cells to activate relaxation [18].
• By contrast, brief (15 min) exposure of endothelial cells, stimulated to secrete EDRF, to homocysteine results in the formation of S-NO-homocysteine, a potent antiplatelet agent and vasodilator [20].

Other interactions of ERAF

• GATA-1 and Oct-1 are required for expression of the human alpha-hemoglobin-stabilizing protein gene [1].
• More recently, AHSP was rediscovered as a highly erythroid Kruppel-like factor (EKLF) -dependent transcript [3].

Analytical, diagnostic and therapeutic context of ERAF

• CONCLUSION: A strategy of approximately 24-hour delay in cardioversion shock timing decreased the incidence of ERAF, relative to a shock delivered within a few hours of AF onset [21].
• We have used isothermal titration calorimetry to show that the interaction is of moderate affinity with an association constant of 1 x 10(7) m(-1) and is thus likely to be biologically significant given the concentration of AHSP (approximately 0.1 mm) and hemoglobin (approximately 4 mm) in the late pro-erythroblast [13].
• AHSP and alpha-globin are both monomeric in solution as determined by analytical ultracentrifugation and bind each other to form a complex with 1:1 subunit stoichiometry, as judged by gel filtration and amino acid analysis [13].
• Nevertheless, EKLF binds this atypical site by gel mobility shift assay, specifically occupies the AHSP promoter in vivo in a chromatin immunoprecipitation assay, and transactivates AHSP through this CACC site in promoter-reporter assays [3].
• The relaxation of the bioassay tissues induced by EDRF was indistinguishable from that induced by NO [19].

References