The homolog of chromatin binding protein Bx42 identified in Dictyostelium.

We identified in Dictyostelium a gene snwA containing a region of similarity to SH2 domains of higher eukaryotes. snwA is homologous to a novel human gene SNW1 and to Bx42 from Drosophila melanogaster, a gene coding for a chromatin binding protein responsive to 20-OH-ecdysone. snwA has one mRNA transcript of an approximate size of 2.5 kb.

The effect of inositol 1,4,5-trisphosphate and inositol 1,4,5-trisphosphorothioate on calcium release and membrane skeleton organization in the human red blood cell.

The inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] content of unstimulated human red blood cells (RBC) has been found to be 227 +/- 83 pmol of Ins(1,4,5)P3 per mL of packed cells. Ins (1,4,5)P3 at concentrations between 0.4-5.0 microM releases Ca2+ from RBC plasma membrane with an EC50 of 0.55 microM. Inositol 4,5-bisphosphate [Ins(4,5)P2] is less potent, but inositol 1-phosphate [Ins(1)P], inositol 1,4-bisphosphate [Ins (1,4)P2], and adenosine triphosphate (ATP) are inactive. The release was stereospecific for D-Ins(1,4,5)P3; 1 microM L-Ins(1,4,5)P3 released no more Ca2+ than the control. A nonhydrolyzable analog of Ins(1,4,5)P3, inositol 1,4,5-trisphosphorothioate [Ins(1,4,5)PS3] evokes sustained release of Ca2+ from isolated ghosts. Release of 45Ca2+ was also observed after the addition of AlF4-. Ionophore A23187 and AlF4- increase the level of Ins(1,4,5)P3 in intact RBC to 1004 +/- 533 and 455 +/- 74 pmol/mL of packed RBC, respectively. We have elaborated a method for visualization of spectrin by indirect immunofluorescence in smears of RBC. Ins(1,4,5)P3 evokes shape changes in permeabilized RBC and disorganization of the spectrin network. The shape changes are stereospecific for the D-enantiomer, since L-Ins(1,4,5)P3 and other compounds had no effect. Whereas the effect of Ins(1,4,5)P3 was reversible, as was the weaker effect of Ins(4,5)P2, Ins(1,4,5)PS3 evoked irreversible shape changes. Shape changes and spectrin disorganization were also observed after the action of AlF4- and ionophore A23187. We conclude that the phosphoinositide signaling system plays an important role in the shape maintenance of human RBC.

Phosphoinositide signalling system in red blood cells of patients with hereditary spherocytosis.

Hereditary spherocytosis (HS) is characterised with many deviations of red blood cells properties. We investigated a group of 14 patients with mild HS, 7 of whom were splenectomised. We found changes in the content and/or turnover of polyphosphoinositides and phosphatidic acid accompanied by the higher generation of inositol 1,4,5-trisphosphate. We suggest that the activation of the phosphoinositide signalling system may be crucial for the manifestation of HS.

Phosphoinositide signalling system in human erythrocyte and its role in cell pathology.

Human erythrocytes contain 217.2 +/- 70.5 pmole of inositol 1,4,5-trisphosphate per ml of packed cells (n = 14). The increased generation of Ins 1,4,5P3, was induced by 1 microM A 23187, 20 microM Pb2+, and by AlF4-. Ins 1,4,5P3, Pb2+ and AlF4- evoke shape changes, disorganisation of spectrin network and vesiculation. In erythrocytes of patients with hereditary spherocytosis the level of Ins 1,4,5P3 was increased to 556.7 +/- 374 pmole per ml of packed cells. We suggest that activation of the phosphoinositide signalling system may represent a common denominator for many divergent stimuli and defects which affect shape changes of erythrocytes.

Transbilayer redistribution of phosphatidylserine in erythrocytes of a patient with autoerythrocyte sensitization syndrome (psychogenic purpura).

We have investigated a female patient with autoerythrocyte sensitization syndrome (AES syndrome), having a positive skin response to her own red blood cells (RBC) and to phosphatidylserine (PS). Using 2,4,6-trinitrobenzenesulfonic acid (TNBS), bee venom phospholipase A2 and merocyanine 540 binding, we have demonstrated that in RBC of patient more than 50% of PS is redistributed into the outer leaflet of the plasma membrane. Using homologous RBC from a healthy donor we were able to induce transbilayer PS redistribution by incubation with the patient plasma. The presence of immunoglobulin E against cardiolipin and PS was proved in patient's plasma. We elaborated a method for cytoskeleton visualization using indirect immunofluorescence technique. We found disorders in cytoskeleton organization in RBC of the patient. We recommend in vitro testing for AES syndrome diagnosis. The positive effect of chlorpromazine treatment is described.