Altered membrane structure and surface potential in homozygous hemoglobin C erythrocytes.
BACKGROUND
Hemoglobin C differs from normal hemoglobin A by a glutamate-to-lysine substitution at position 6 of beta globin and is oxidatively unstable. Compared to homozygous AA erythrocytes, homozygous CC erythrocytes contain higher levels of membrane-associated hemichromes and more extensively clustered band 3 proteins. These findings suggest that CC erythrocytes have a different membrane matrix than AA erythrocytes.


RESULTS
We found that AA and CC erythrocytes differ in their membrane lipid composition, and that a subset of CC erythrocytes expresses increased levels of externalized phosphatidylserine. Detergent membrane analyses for raft marker proteins indicated that CC erythrocyte membranes are more resistant to detergent solubilization. These data suggest that membrane raft organization is modified in CC erythrocytes. In addition, the average zeta potential (a measure of surface electrochemical potential) of CC erythrocytes was approximately 2 mV lower than that of AA erythrocytes, indicating that substantial rearrangements occur in the membrane matrix of CC erythrocytes. We were able to recapitulate this low zeta potential phenotype in AA erythrocytes by treating them with NaNO(2) to oxidize hemoglobin A molecules and increase levels of membrane-associated hemichromes.


CONCLUSIONS
Our data support the possibility that increased hemichrome deposition and altered lipid composition induce molecular rearrangements in CC erythrocyte membranes, resulting in a unique membrane structure.
Tokumasu
Fuyuki
F
Biophysical and Biochemical Parasitology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America. ftokumasu@niaid.nih.gov
Nardone
Glenn A
GA
Ostera
Graciela R
GR
Fairhurst
Rick M
RM
Beaudry
Steven D
SD
Hayakawa
Eri
E
Dvorak
James A
JA
D003902:Detergents / Q000494:pharmacology; D004563:Electrochemistry / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000378:metabolism*; D005434:Flow Cytometry; D005971:Glutamates / Q000737:chemistry; D006444:Hemoglobin C / Q000235:genetics*; D006720:Homozygote; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D010641:Phenotype
D003902:Detergents; D005971:Glutamates; D008055:Lipids; D008563:Membrane Lipids; D006444:Hemoglobin C; D008239:Lysine; D010100:Oxygen