Ubiquitin aldehyde increases adenosine triphosphate-dependent proteolysis of hemoglobin α-subunits in β-thalassemic hemolysates

• Published in: Blood Vol. 90; no. 3; pp. 1300 - 1308
• Main Authors: SHAEFFER, J. R, COHEN, R. E
• Format: Journal Article
• Language: English
• Published: Washington, DC The Americain Society of Hematology 01.08.1997
• Subjects: Adenosine Triphosphate - physiology; Anemias. Hemoglobinopathies; beta-Thalassemia - blood; beta-Thalassemia - genetics; Biological and medical sciences; Carbon-Nitrogen Lyases; Cell-Free System; Diseases of red blood cells; Drug Evaluation, Preclinical; Endopeptidases - blood; Globins - metabolism; Hematologic and hematopoietic diseases; Hemoglobin A - metabolism; Hemolysis; Humans; Lyases - antagonists & inhibitors; Lyases - blood; Medical sciences; Stimulation, Chemical; Ubiquitins - analogs & derivatives; Ubiquitins - pharmacology; Human; Ubiquitin; Hemoglobinopathy; Enzyme; Enzyme inhibitor; Hemopathy; Aldehyde; Genetic disease; Peptidases; Hemolytic anemia; β-Thalassemia; Proteolysis; Hemoglobin; Hydrolases; Alpha-Peptide chain; ATP
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.v90.3.1300

Two major causes of the anemia in beta-thalassemia are a deficiency in hemoglobin (Hb) beta-subunit (and consequently HbA) synthesis and, due to the resulting excess of Hb alpha-subunits, erythroid cell hemolysis. The hemolytic component might be ameliorated by increasing the intracellular proteolysis of the excess alpha-subunits. Isolated 3H-labeled alpha-chains are known to be degraded primarily by the adenosine triphosphate (ATP)- and ubiquitin (Ub)-dependent proteolysis pathway in unfractionated beta-thalassemic hemolysates. Our objective was to increase this degradation by targeted intervention. Ub aldehyde (Ubal), a synthetic inhibitor of isopeptidases (proteases that hydrolyze the bond between the Ub polypeptide and its protein adduct), was added to reaction mixtures containing a hemolysate from the blood cells of one of four beta-thalassemic donors and 3H-alpha-chains or 3H-alpha-globin as a substrate. Optimum enhancement of ATP-dependent degradation occurred at 0.4 to 1.5 micromol/L Ubal and ranged from 29% to 115% for 3H-alpha-chains and 47% to 96% for 3H-alpha-globin among the four hemolysates. We suggest that Ubal stimulates 3H-alpha-subunit proteolysis by inhibition of an isopeptidase(s) that deubiquitinates, or "edits," Ub-3H-alpha-subunit conjugates, intermediates in the degradative pathway. In control studies, similarly low Ubal concentrations did not enhance the degradation of 3H-alpha2beta2 (HbA) tetramers or inhibit the activities of methemoglobin reductase and four selected glycolysis pathway enzymes. These and other results may be the basis for a therapeutic approach to beta-thalassemia.