Changes in membrane polypeptides, polyphosphoinositides and phosphatidate in dense fractions of sickle cells

Increased membrane activity of glyceraldehyde 3-phosphate dehydrogenase in erythrocytes of patients with homozygous sickle cell anaemia

Membrane-bound glyceraldehyde 3-phosphate dehydrogenase activity was measured in erythrocytes from 43 patients with sickle cell anaemia, 24 heterozygous and 27 controls. A significant increase of the activity was found among the patients but no such difference was observed between the heterozygous and the control individuals. The patients showed nearly non Gaussian distribution of the enzyme activity and were subgrouped on the basis of these results, subgroup I had normal values and subgroup II showed markedly increased activities. The patients in subgroup II had significantly lower blood haemoglobin concentrations and significantly higher lactate dehydrogenase activities in serum than subgroup I. The subgroups did not differ in blood reticulocyte counts, serum bilirubin, serum iron concentrations or band 3 protein content of erythrocyte membranes.

Sickle cell anaemia in Sudan: clinical findings, haematological and serum variables

Ninety homozygous patients with Hb S haemoglobinopathy from Sudan were reported with respect to clinical findings, haematological and serum parameters. For comparison, 27 Hb AS heterozygous subjects and 28 Hb AA controls were investigated also. The patients showed an extreme type of illness presenting with severe clinical signs such as dactylitis, liver enlargement and cardiac complications. There was marked haemolytic anaemia (mean haemoglobin 66 g/l). Some patients also presented with low serum (S)-iron levels, indicating iron deficiency. S-bilirubin, S-ASAT, S-ALAT, S-GT and S-urate were notably raised, most probably as a consequence of haemolysis with liver involvement. The patients had lower S-calcium levels when compared with the AS and AA subjects. This may suggest a possible role of HB S in the production of this feature.

Reduction in band 3 protein of red cells in sickle cell anaemia

Twelve patients suffering from sickle cell anaemia (Hb less than 75 g/l) with SS-haemoglobin were studied with special regard to Band 3-protein content in their erythrocyte membranes on SDS-PAGE. They were compared in this respect with 7 asymptomatic individuals with AS-haemoglobin and 10 healthy controls with the ordinary adult haemoglobin. A heterogeneity in Band 3-protein content was evident among the 12 patients. Six of them belonged to a low content group while the other 6 belonged to a high content group comparable with the asymptomatic subjects and the controls. No simple relationship seemed to exist between Band 3-protein reduction and the clinical presentation.

Red cell membrane phosphatidylinositol kinase activity in hemolytic anemias and myeloproliferative diseases

Phosphatidylinositol kinase activity was determined in red cell membranes from 85 healthy individuals, 20 patients with hereditary hemolytic anemia and 24 patients with myeloproliferative disorder. Increased activity was found in all ten cases of sickle red disease and seven among ten cases of other hereditary hemolytic anemias. These increases had no correlation with the reticulocyte count nor with the red cell shape. An unexpected decreased activity was found in several cases of myeloproliferative disorders, especially in polycythemia vera, with a negative correlation with the reticulocyte count. The mechanism(s) and significance of the phosphatidylinositol kinase abnormalities in these different groups of diseases remain to determine.

Endogenous calcium in sickle cells does not activate polyphosphoinositide phospholipase C

Sickle-cell-anaemia erythrocytes (SS cells) are known to have a high Ca2+ content (particularly the dense cell fraction) and to take up Ca2+ on deoxygenation. It has been reported that this high Ca2+ was responsible for the activation of the Ca2+-dependent K+ loss, and of the Ca2+-sensitive polyphosphoinositide phospholipase C (PIC) in dense SS cells. We found that, either in the total population of SS cells or in the light or dense fractions, the content of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] was not changed, whereas that of phosphatidylinositol 4-phosphate was increased and that of phosphatidic acid (PtdOH) was decreased compared with normal (AA) erythrocytes. Deoxygenation-induced Ca2+ entry into SS cells did not change the concentration or, in 32P-prelabelled cells, the radioactivity of polyphosphoinositides and PtdOH. It also failed to induce the formation of inositol 1,4,5-trisphosphate, the product of PtdIns(4,5)P2 hydrolysis by PIC, which was measured by an original method using ion-pair reverse-phase h.p.l.c. Thus there was no evidence of an endogenous Ca2+ effect on the PIC activity in SS cells, in agreement with the demonstration that the excess Ca2+ in SS cells is compartmentalized into internal vesicles and unavailable as free Ca2+. The 32P incorporation in polyphosphoinositides and PtdOH was markedly higher in SS than in AA cells, but this increase was the same in both dense and light SS cells. The increase in the turnover of these phospholipids in SS cells is consistent either with an activation of the lipid kinases and phosphatases or with perturbation in the metabolic compartmentation of these lipids.

Increased membrane-associated phorbol-12,13 dibutyrate (PDBu) receptor function in sickle red cells

A four-fold increase in the binding of 3H-PDBu by red cell membrane ghosts isolated from sickle red cells compared to that from normal controls is presented. Phosphorylation studies with gamma-32P-ATP indicate a similar (two to three-fold) increase in the radiolabelling of the acid-precipitable membrane proteins in sickle red cells. When red cells were loaded with Ca2+ using Ionophore A23187, both normal and sickle red cells enhanced their phosphorylation and sickle red cells to a greater extent than normal red cells. Polyacrylamide slab gel electrophoretic separation of the phosphoproteins and autoradiography also reveal phosphorylation, predominantly of protein bands 3, 4.1 and 4.9 which are known in the red cells as specific substrates for the PDBu receptor, protein kinase C. These results indicate that membrane association of protein kinase C in sickle red cells is increased, possibly as a consequence of the pathological change in their ability to accumulate intracellular calcium.