Irreversible AE1 tyrosine phosphorylation leads to membrane vesiculation in G6PD deficient red cells.
BACKGROUND
While G6PD deficiency is one of the major causes of acute hemolytic anemia, the membrane changes leading to red cell lysis have not been extensively studied. New findings concerning the mechanisms of G6PD deficient red cell destruction may facilitate our understanding of the large individual variations in susceptibility to pro-oxidant compounds and aid the prediction of the hemolytic activity of new drugs.


RESULTS
Our results show that treatment of G6PD deficient red cells with diamide (0.25 mM) or divicine (0.5 mM) causes: (1) an increase in the oxidation and tyrosine phosphorylation of AE1; (2) progressive recruitment of phosphorylated AE1 in large membrane complexes which also contain hemichromes; (3) parallel red cell lysis and a massive release of vesicles containing hemichromes. We have observed that inhibition of AE1 phosphorylation by Syk kinase inhibitors prevented its clustering and the membrane vesiculation while increases in AE1 phosphorylation by tyrosine phosphatase inhibitors increased both red cell lysis and vesiculation rates. In control RBCs we observed only transient AE1 phosphorylation.


CONCLUSIONS
Collectively, our findings indicate that persistent tyrosine phosphorylation produces extensive membrane destabilization leading to the loss of vesicles which contain hemichromes. The proposed mechanism of hemolysis may be applied to other hemolytic diseases characterized by the accumulation of hemoglobin denaturation products.
Department of Genetics, Biology and Biochemistry, University of Turin, Turin, Italy.
Antonella
A
Pantaleo
Emanuela
E
Ferru
Franco
F
Carta
Franca
F
Mannu
Luigi F
LF
Simula
Amina
A
Khadjavi
Proto
P
Pippia
Francesco
F
Turrini
D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000473:pathology* / Q000648:ultrastructure; D005955:Glucosephosphate Dehydrogenase Deficiency / Q000473:pathology*; D006454:Hemoglobins / Q000378:metabolism; D006461:Hemolysis; D006801:Humans; D016877:Oxidants / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D001457:Anion Exchange Protein 1, Erythrocyte; D006454:Hemoglobins; D016877:Oxidants; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases
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