Role of hemichrome binding to erythrocyte membrane in the generation of band-3 alterations in beta-thalassemia intermedia erythrocytes.
Nine splenectomized, hematologically well-compensated beta-thalassemia intermedia patients randomly chosen from a pool of 60 similar patients were studied. Membrane proteins solubilized with nondenaturing detergent C12E8 were gel filtered on Sepharose CL-6B (Pharmacia Fine Chemicals, Uppsala, Sweden). Fractions containing higher than 4,000-kD molecular-weight aggregates were isolated and analyzed. Four patients had remarkably increased amounts of membrane-bound hemichromes and Igs. In those patients, band 3 underwent oxidative modifications such as aggregation and a decrease in sulfhydryl groups. The other five patients had low amounts of membrane-bound hemichromes and less modifications of band 3. The same band-3 modifications could be reproduced by challenging normal membranes with artificially generated hemichromes or with hemolysates prepared from thalassemic erythrocytes of the high-hemichrome group. Addition of reduced glutathione to the challenged membranes did not hinder hemichrome binding, but prevented oxidative modifications of band 3 and Ig binding to high-molecular-weight band-3 aggregates. Hemichrome binding to band 3, hemichrome-mediated oxidation of band-3 cytoplasmic domains, generation of high-molecular-weight band-3 aggregates, and enhanced opsonization by anti-band-3 antibodies is a possible sequence of events leading to phagocytic removal of erythrocytes in thalassemia.
Mannu
F
F
Department of Genetics, Biology, Medical Chemistry, University of Torino Medical School, Italy.
Arese
P
P
Cappellini
M D
MD
Fiorelli
G
G
Cappadoro
M
M
Giribaldi
G
G
Turrini
F
F
D000293:Adolescent; D000328:Adult; D001457:Anion Exchange Protein 1, Erythrocyte / Q000302:isolation & purification / Q000378:metabolism*; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005260:Female; D005838:Genotype; D006420:Hemeproteins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000097:blood* / Q000302:isolation & purification; D008970:Molecular Weight; D017086:beta-Thalassemia / Q000097:blood* / Q000235:genetics
D001457:Anion Exchange Protein 1, Erythrocyte; D006420:Hemeproteins; D008565:Membrane Proteins; C001332:hemichrome