Abnormality in a specific protein of the erythrocyte membrane in hereditary spherocytosis

Induction of erythrocyte protein 4.2 gene expression during differentiation of murine erythroleukemia cells

Protein 4.2 (P4.2) is an important component in the erythrocyte membrane skeletal network that regulates the stability and flexibility of erythrocytes. Recently, we provided the evidence for specific P4.2 expression in erythroid cells during development (L. Zhu et al., 1998, Blood 91, 695-705). Using dimethyl sulfoxide (DMSO)-induced differentiation of murine erythroleukemia (MEL) cells as a model, transcription of the P4.2 gene was found to be induced during erythroid differentiation. To examine the mechanism for this induction, we isolated the mouse P4.2 genomic DNA containing the 5' flanking sequence and defined the location of the P4.2 promoter. Transcription of the mouse P4.2 gene initiates at multiple sites, with the major initiation site mapped at 174 nucleotides upstream of the ATG start codon. The mouse P4.2 promoter is TATA-less and contains multiple potential binding sites for erythroid transcription factors GATA-1, NF-E2, EKLF, and tal-1/SCL. Transient transfection experiments demonstrated that a 1.7-kb mouse P4.2 promoter fused with the luciferase coding regions was induced in DMSO-treated MEL cells. Deletion analysis showed that a 259-bp P4.2 promoter DNA (nucleotide position -88 to +171 relative to the major transcription initiation site designated +1), containing a GATA-binding site at position -29 to -24, could still respond to the induction in differentiated MEL cells. Importantly, mutations in the -29/-24 GATA motif rendered the promoter unresponsive to DMSO induction. Electrophoretic mobility shift assay revealed that GATA-1 could bind to the -29/-24 GATA motif and this was confirmed by the observation that the nuclear protein bound to the motif was supershifted by an anti-GATA-1 monoclonal antibody. Taken together, these results suggest that the erythroid transcription factor GATA-1 plays an important role in the induction of P4.2 gene expression during erythroid cell differentiation.

Electron microscopic evidence of impaired intramembrane particles and instability of the cytoskeletal network in band 4.2 deficiency in human red cells

To obtain direct evidence of impaired intramembrane particles (IMPs) and a deranged cytoskeletal network in situ in human red cells of band 4.2 deficiency, electron microscopic studies were performed utilizing the freeze fracture method for IMPs and the quick-freeze deep-etching method for the cytoskeletal network. Three patients with three different previously identified mutations of the band 4.2 gene, i.e., band 4.2 Komatsu (homozygous; codon 175 GAT --> TAT), band 4.2 Nippon (homozygous; codon 142 GCT --> ACT), and band 4.2 Shiga (compound heterozygous; codon 317 CGC --> TGC and codon 142 GCT --> ACT), were selected for this study. The decrease in the number of IMPs with increase in their size was most marked in band 4.2 Komatsu, which was clinically most severe with no band 4.2 protein. In this regard, in band 4.2 Nippon, which showed moderate severity in clinical hematology with a nearly missing band 4.2 protein, increased sizing was less marked. The abnormalities in IMPs were the least in band 4.2 Shiga, which demonstrated compensated hemolysis with band 4.2 protein in a trace amount. The extent of the impairment of IMPs may be reflected by the total absence or the presence of band 4.2 protein even in a trace amount and/or by the specific site(s) of the mutation of the band 4.2 gene. Derangement of the cytoskeletal network was also observed in these three patients. It was most abnormal in band 4.2 Komatsu, and less so in band 4.2 Nippon and in band 4.2 Shiga. These results clearly indicate that 1) band 4.2 plays an important role not only in its binding to band 3 but also to the skeletal network (mostly to spectrins) vertically, and 2) its deficiency produces critical abnormality in maintenance of the structural and functional integrity of the integral proteins (such as band 3), as well as the cytoskeletal network.

Band 4.2 Shiga: 317 CGC-->TGC in compound heterozygotes with 142 GCT-->ACT results in band 4.2 deficiency and microspherocytosis

A novel compound heterozygous mutation of 317 CGC-->TGC with 142 GCT-->ACT in human red cell band 4.2 deficiency is described. A proband and his son suffered from compensated haemolysis with nearly complete deficiency of red cell band 4.2. Their red cell morphology exhibited microspherocytosis resembling classic hereditary spherocytosis (HS). Sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed band 4.2 to be nearly missing (< 1% of normal controls) with the presence of 74 kD and 72 kD isoforms in trace amounts. Other family members (daughters older and younger than the son) exhibited nearly normal amounts of 72kD as a wild form of band 4.2 on SDS-PAGE with the presence of the 74kD isoform in a trace amount. The proband and his son demonstrated two compound heterozygous mutations in trans: i.e. nucleotide (nt) 949 CGC-->TGC (codon 317 Arg-->Cys) in exon 7 and nt 424 GCT--ACT (codon 142 Ala-->Thr) in exon 3 of the band 4.2 gene. The two daughters demonstrated only the mutation of nt 949 CGC-->TGC in exon 7 in heterozygous states, but no 142 mutation. Therefore the proband and his son were compound heterozygotes of these two mutations in trans. It is interesting to note that the 74 kD isoform of band 4.2 protein existed in a trace amount in the two daughters in spite of the absence of the 142 Ala-->Thr mutation. In addition, even in the presence of the 142 mutation in one allele in the proband and his son, their red cell morphology demonstrated classic HS with microspherocytosis, although a homozygous state of the 142 mutation known as the Nippon type of band 4.2 deficiency exhibits ovalostomatocytosis.

A novel mutation in the erythrocyte protein 4.2 gene of Japanese patients with hereditary spherocytosis (protein 4.2 Fukuoka)

Human erythrocyte protein 4.2 (band 4.2; pallidin) is a major membrane protein that comprises 5% of the total weight of the human erythrocyte membrane. Deficiencies of this protein have been observed in hereditary spherocytosis with anaemia, suggesting a role of protein 4.2 in erythrocyte stability and integrity. The molecular basis of this disorder remains unknown. As a first step in elucidating the pathogenesis of hereditary spherocytosis associated with protein 4.2 deficiency, we cloned and sequenced the erythrocyte protein 4.2 gene from a normal Japanese person. We prepared sets of oligonucleotide primers for polymerase chain reaction (PCR) and determined nucleotide sequences of exons and exon-intron boundaries of the protein 4.2 gene from three unrelated Japanese patients with hereditary spherocytosis due to a complete defect of protein 4.2, using PCR-related techniques. Two patients were homozygous for a missense mutation in codon 142 with the Ala (GCT)-->Thr (ACT) amino acid substitution that has been reported previously (protein 4.2NIPPON), whereas one patient was compound heterozygous for the same missense mutation in codon 142 and a guanine-adenine transition in codon 119 that changes the codon for Trp (TGG) to the termination codon (TGA) (protein 4.2Fukuoka). No additional mutation was identified in other exons of the protein 4.2 genes. Dot-blot hybridization with allele-specific oligonucleotide probes showed that homozygosity for the missense mutation in codon 142 and compound heterozygosity for the codon 142 and the codon 119 mutations were related to protein 4.2 deficiency in the families. Although two alleles of missense mutation of the codon 142 were also detected in 100 alleles of healthy Japanese, results obtained in this study indicate that the two mutations described above are closely related to the pathogenesis of hereditary spherocytosis due to protein 4.2 defect.

Hereditary spherocytosis: diagnostic and anaemia-associated aberrations of ghost proteins

Various disorders of the red cell skeleton and membrane have been described in hereditary spherocytosis. To elucidate which aberrations could be used for identification of HS patients in a Danish population, we examined ghosts from 17 HS patients and 20 normals by use of SDS-gel scanning, native spectrin extraction, and limited tryptic digestion. Compared to normals, HS patients had significantly lowered alpha-spectrin (p < 0.004), protein 4.2 (p < 0.025), and actin (p < 0.05), and significantly increased anion-transporter (p < 3 x 10(-6)) and glyceraldehyde-3-phosphate dehydrogenase (G3PD, p < 0.04). Sixteen out of 17 HS patients could be identified by aberrations of the anion-transporter or protein 4.2 outside a 95% confidence interval for normals. Extraction of native spectrin and limited tryptic digest showed no difference between normals and HS patients. RBC separated into young and old fractions were used to examine the occurrence of protein aberrations associated with RBC age. Young RBC contained more G3PD (35%) and less protein 4.1 (6.5%) and actin (8.7%) than old. In male HS patients an increased G3PD content showed a linear correlation (p < 0.001) with a low concentration of blood haemoglobin. We conclude that aberrations of G3PD, and possibly protein 4.1, and actin, are associated with anaemia in HS. Increased anion-transporter or lowered protein 4.2 may be useful for diagnosis of HS, and were inherited in five out of six families where two generations were available.

Band 4.2 abnormalities in human red cells

Abnormalities of membrane protein band 4.2 in human red cells are reviewed from the standpoints of clinical hematology, protein chemistry, membrane functions, and gene expression. This article will help more extensive investigations in clarifying the physiologic significance of this protein, and to understand abnormalities of band 4.2 in clinical, biochemical, biologic, and genetic aspects.

Red cell membrane protein band 4.2: phenotypic, genetic and electron microscopic aspects

The present status of band 4.2 has been reviewed from the standpoint of protein chemistry, gene analysis and clinical hematology. Band 4.2 plays an important role in various cellular functions. In 142 GCT-->ACT band 4.2 deficiency, abnormalities of the cytoskeletal network were clearly observed by electron microscopy and by ektacytometry, although the cytoskeletal proteins themselves were essentially normal in these red cells. The physiological states of band 3 in situ in the membranes were also affected in band 4.2 deficiency, as detected by electron microscopy, although again the biochemical properties of band 3 itself were essentially normal in these red cells. Other disorders of band 4.2 deficiency in the absence of the 142 GCT-->ACT mutation appear to be most interesting in the pathogenesis of hemolysis. In some of the band 4.2 anomalies, other membrane proteins including band 3 would appear to be most pathognomonic for the disease states. These conditions require elucidation by protein chemistry and gene analysis. The control mechanism of the gene expression should also be clarified to understand the important role of band 4.2 in health and disease.

Structural domain mapping and phosphorylation of human erythrocyte pallidin (band 4.2)

Pallidin (band 4.2) is a major protein of the human erythrocyte membrane, and plays an important but as yet undefined role in maintaining the normal shape and lifespan of the erythrocyte. The pallidin protein has been purified by a new procedure which yields a protein which is > 97% pure as judged by gel electrophoresis, while pallidin purified by our original procedure is only approx. 85% pure. The new form of the protein is unstable in physiological salt solutions. However, taking advantage of its high purity, we have used the new form of the protein to produce a structural domain map of its principal tryptic fragments. We also show that pallidin can be phosphorylated by a red-cell membrane kinase which partially co-purifies with it, and has properties similar to the catalytic subunit of cAMP-dependent kinase. Both cAMP-dependent kinase and the red-cell kinase phosphorylate the same tryptic domains on the pallidin protein. Our results show that endogenous pallidin on the red-cell membrane is a poor substrate for the kinase, possibly because it is fully phosphorylated, or inaccessible to the kinase.

Point mutation in the band 4.2 gene associated with autosomal recessively inherited erythrocyte band 4.2 deficiency

A patient who represented acute hemolytic crisis was studied. Analysis of the erythrocyte membrane proteins by SDS-PAGE revealed a deficiency of band 4.2. In the family, the sister of the patient who had been clinically normal was also shown to be deficient in band 4.2. Binding studies showed that the propositus' membranes were able to bind normal band 4.2 protein as much as control. It was suggested that the binding sites for the protein were prepared on the membrane. We analyzed the band 4.2 cDNA of the propositus and detected a mutation that changes a codon for alanine to one for threonine at residue 142. Band 4.2 exon III of genomic DNA which included the mutation site was amplified and sequenced directly in the family members, and it was revealed that only the homozygotes of the mutation allele manifested band 4.2 deficiency and the parents, who were heterozygotes, showed normal amounts of band 4.2. Recently, the same mutation was reported as Protein 4.2NIPPON in another 4 cases (Bouhassira et al. Blood 1992: 79: 1846-1854). This study supports the hypothesis that this mutation is the pathogenetic cause of band 4.2 deficiency and not a polymorphism.

A haemolytic syndrome associated with the complete absence of red cell membrane protein 4.2 in two Tunisian siblings

We report on the complete absence of protein 4.2 in two Tunisian siblings. The propositus presented with a haemolytic anaemia that evolved in an intermittent fashion until she was cured by splenectomy. Her red cells had a normal morphology, as well as normal deformability upon osmotic gradient ektacytometry. SDS-polyacrylamide gel electrophoresis failed to reveal any protein 4.2. Using anti-protein 4.2 polyclonal antibodies. Western blots were also unable to detect protein 4.2. Preparation of inside out vesicles resulted in no detectable loss of ankyrin. The propositus's sister presented with a haemolytic anaemia but had not undergone splenectomy; she showed the same biochemical features. The two cases presented of missing protein 4.2 are the first ones to be described outside the Japanese population. Considered as homozygotes for some defect that must alter the protein 4.2 gene itself, they exemplify a unique syndrome pertaining neither to elliptocytosis nor to spherocytosis, at least not closely. The parents, who are first cousins and whom we regarded as heterozygotes, were clinically and morphologically normal; they had a normal content of protein 4.2. Therefore, the 4.2 (-) haemolytic anaemia appears as entirely recessive.

A genetic defect of erythrocyte band 4.2 protein associated with hereditary spherocytosis

We report two patients with hereditary spherocytosis associated with band 4.2 protein deficiency from a Japanese family. The defect of band 4.2 protein was confirmed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) not only in freshly prepared white ghosts but also in washed whole erythrocytes. The finding was quite reproducible and was also recognized postsplenectomy. The interaction of ankyrin with band 3 in the patients' ghosts was stable both at low ionic strength and at acidic pH. Our results suggested that band 4.2 protein might not be essential for the structural stability of band 3-ankyrin interaction. On the other hand, membrane protein phosphorylation studies revealed an increased phosphorylation of spectrin/ankyrin, band 3 and band 4.1 in the patients' erythrocytes as compared with normal cells. The finding might be related to a dysregulation of protein phosphorylation which could result in membrane instability in affected cells. Band 4.2 deficiency is an inherited disorder in association with hereditary haemolytic anaemias and seems to be relatively prevalent in the Japanese population.

Complete amino acid sequence and homologies of human erythrocyte membrane protein band 4.2

The complete amino acid sequence for human erythrocyte band 4.2 has been derived from the nucleotide sequence of a full-length 2.35-kilobase (kb) cDNA. The 2.35-kb cDNA was isolated from a human reticulocyte cDNA library made in the expression vector lambda gt11. Of the 2348 base pairs (bp), 2073 bp encode 691 amino acids representing 76.9 kDa (the SDS/PAGE molecular mass is 72 kDa). RNA blot analysis of human reticulocyte total RNA gives a message size for band 4.2 of 2.4 kb. The amino acid sequence of band 4.2 has homology with two closely related Ca2(+)-dependent cross-linking proteins, guinea pig liver transglutaminase (protein-glutamine gamma-glutamyltransferase; protein-glutamine: amine gamma-glutamyltransferase, EC 2.3.2.13) (32% identity in a 446-amino acid overlap) and the a subunit of human coagulation factor XIII (27% identity in a 639-amino acid overlap), a transglutaminase that forms intermolecular gamma-glutamyl-epsilon-lysine bonds between fibrin molecules. The region of greatest identity includes a 49-amino acid stretch of band 4.2, which is 69% and 51% identical with guinea pig liver transglutaminase and the a subunit of factor XIII, respectively, within the regions that contain the active sites of these enzymes. Significantly, within the five contiguous consensus residues of the transglutaminase active site, Gly-Gln-Cys-Trp-Val, band 4.2 has an alanine substituted for cysteine (which is apparently essential for activity). Consistent with this active site substitution, erythrocyte membranes or inside-out vesicles, which contain band 4.2, show no evidence of transglutaminase activity by two types of in vitro assay.

Deficiency of protein 4.2 in erythrocytes from a patient with a Coombs negative hemolytic anemia. Evidence for a role of protein 4.2 in stabilizing ankyrin on the membrane

A patient with a mild hemolytic anemia and osmotically fragile, spherocytic erythrocytes was studied. Analysis of the erythrocyte membrane proteins by SDS-PAGE revealed a deficiency of protein 4.2 (less than 0.10% of normal). The protein 4.2-deficient erythrocytes contained normal amounts of all other membrane proteins, although the amount of band 3 was slightly reduced and the amount of band 6 (G3PD) was slightly elevated. The spectrin content of these cells was normal, as measured by both SDS-PAGE and radioimmunoassay. Erythrocytes from the patient's biologic parents were hematologically normal and contained normal amounts of protein 4.2. Immunological analysis using affinity purified antibodies revealed that the patient's protein 4.2 was composed of equal amounts of a 74-kD and 72-kD protein doublet, whereas the normal protein was composed primarily of a 72-kD monomer. Proteolytic digestion studies using trypsin, alpha-chymotrypsin and papain demonstrated that the patient's protein 4.2 was similar but not identical to the normal protein. Binding studies showed that the protein 4.2-deficient membranes bound purified protein 4.2 to the same extent as normal membranes, suggesting that the membrane binding site(s) for the protein were normal. Depleting the protein 4.2-deficient membranes of spectrin and actin resulted in a loss of nearly two-thirds of the membrane ankyrin, whereas similar depletion of normal membranes resulted in no loss of ankyrin. Repletion of the protein 4.2-deficient membranes with purified protein 4.2 before spectrin-actin extraction partially prevented the loss of ankyrin. These results suggest that protein 4.2 may function to stabilize ankyrin on the erythrocyte membrane.

Abnormal degradation of erythrocyte membrane proteins in hereditary spherocytosis

The degradation rate of erythrocyte membrane proteins by membrane-bound proteases was compared in healthy controls and in patients with hereditary spherocytosis (HS). An increased degradation rate of spectrin and a decreased digestion rate of Band 3 were found in HS patients. These differences may be due to altered accessibilities of membrane proteins to proteases and/or to changes in the pattern of membrane-associated proteases and may be connected with the decrease in the spectrin: Band 3 ratio reported for erythrocyte membranes in HS.

A phenomenological difference between membrane skeletal protein complexes isolated from normal and hereditary spherocytosis erythrocytes

Membrane skeletons may be obtained from human erythrocytes by extraction with non-ionic detergent. When treated under defined conditions with a cAMP-independent kinase preparation from normal membranes, a suspension of these membrane skeletons sets to a gelatinous mass. Membrane skeletons from the cells of hereditary spherocytosis patients fail to show this response. Those from subjects with some other haemolytic anaemias do not share the abnormality. The gelation process could be shown also to occur with normal membrane skeletons, extracted at high ionic strength, and containing essentially only the structural protein constituents, spectrin, actin, 4.1 and 4.9. It also occurred rapidly when a column-purified kinase preparation was used, so that no significant amounts of contaminating proteins were introduced. Added spectrin, 4.1 or actin in moderate amounts did not induce gelation in the presence of ATP. Cytochalasin E did not perturb the gelation process. Gelation required ATP as well as kinase, and did not occur when the non-hydrolysable analogue, AMP X PNP, was used instead. Gelation was accompanied by phosphorylation of the spectrin alone, and is thus evidently a consequence of the modification of its properties by this means. Inhibition of phosphorylation by added adenosine retarded gelation. It may be inferred that phosphorylation of spectrin generates new, probably weak, non-covalent interactions between cytoskeletal constituents that cause association of the isolated cytoskeletons. A semi-quantitative method of observing the gelation process, based on the time of incubation before the membrane skeleton suspension ceases to flow under gravity at a low shear, is described.

Erythrocyte membrane skeleton abnormalities in hereditary spherocytosis

Erythrocyte ghosts from eight individuals with hereditary spherocytosis have been compared with respect to their protein compositions as judged by SDS gel electrophoresis, their ease of spectrin extractability, and their freeze-etch electron microscopic appearance after incubation in condition designed to promote aggregation of the intramembrane particles. Four of these HS cases were unrelated, while the other four represented two generations from a single family, including a pair of identical twins, one of whom had not undergone splenectomy when this investigation was initiated. Of the four unrelated cases, one showed no departures from normal under the conditions of this investigation, whereas the other three exhibited features which suggested a membrane skeleton lesion. In one of these there was a reduced proportion of spectrin tetramers relative to dimers in 4 degrees C extracts, while the two remaining cases exhibited abnormal intramembrane particle aggregation. The four related cases had almost identical variations from normal. Spectrin was not extractable from their ghost membranes during a mild extraction incubation which removed spectrin from normal control ghosts. However, the intramembrane particle aggregation subsequently induced in these ghosts was of a degree unobtainable in normal ghosts without such spectrin extraction. In addition the ghosts from one twin, the only one of these patients who had not undergone splenectomy at the start of this investigation, showed a reduced amount of band 4.2. However, when this patient's blood was re-tested after splenectomy, this protein was found to be at normal levels. Our results support the view that hereditary spherocytosis is not a single disease, but is rather a term used to describe a variety of different molecular lesions of the erythrocyte membrane skeleton with similar clinical manifestations.

A genetic defect in the binding of protein 4.1 to spectrin in a kindred with hereditary spherocytosis

Indirect evidence suggests that the genetic defect in hereditary spherocytosis lies in the erythrocyte membrane skeleton, a submembranous meshwork of proteins (principally spectrin, actin, and protein 4.1) responsible for membrane shape and structural stability. To test this premise we systematically assayed the interactions of spectrin, the major skeletal protein, in six kindreds with autosomal dominant hereditary spherocytosis. In one these kindreds, enhancement of spectrin-actin binding by protein 4.1 was reduced, owing to a 39 +/- 4 per cent decrease (mean +/- S.D) in the binding of normal protein 4.1 by spectrin, in all of four members with the disorder. The defective spectrin was separated into two populations by affinity chromatography on immobilized normal protein 4.1. One population (41 +/- 2 per cent) lacked the ability to bind 4.1, but the other functioned normally. Presumable, the nonfunctional spectrin was the product of the autosomal dominant gene responsible for the hereditary spherocytosis in this kindred.

Inherited disorders of the red cell membrane skeleton

Current knowledge of red cell membrane structure and function are briefly presented, and the pathophysiology, diagnosis, and treatment of hereditary spherocytosis, hereditary elliptocytosis, and hereditary pyropoikilocytosis are discussed.

Inhibition of malaria parasite invasion into erythrocytes pretreated with membrane-active drugs

Normal rhesus monkey erythrocytes were incubated with various membrane-active drugs (for 1 h at 37 degrees C) and after thorough washing, were exposed to infection with Plasmodium knowlesi in an invitro cultivation system. The ability of merozoites to infect with drug-pretreated erythrocytes was assessed both by counting the number of infected cells and by measuring the incorporation of [3H]isoleucine into parasite protein. Marked inhibition of invasion was observed with vinblastine and colchicine, at concentrations greater than 5 x 10(-4) M, respectively. At similar concentrations, cytochalasin B or amantadine had no apparent effect. The addition of 10(-3) M 3',5'-cAMP to the medium during the incubation in the presence of colchicine or vinblastine partially decreased the inhibitory effects. The effects of colchicine and vinblastine on parasite invasion may be correlated with a reversible alteration in erythrocyte conformation (spherocytosis) which occurs at similar drug concentrations to those above and which can be relieved by simultaneous incubation with cAMP. A possible mechanism of action is proposed.

Red cell membrane in hemolytic disease. Studies on variables affecting electrophoretic analysis

Significant alterations in the spectrin: band 3 and band 4.1a: band 4.1b ratios and an occasional decrease in the peak height of band 4.2 with respect to band 4.1 were found in electrophoretic patterns of red cell membranes from patients with hereditary xerocytosis. Electrophoretic comparison of whole cell, cytoplasm and membrane polypeptides implied that atypical partitioning at hemolysis could account for some, but not all, of the alterations seen in membrane patterns of xerocytes. A decrease in band 4.2 peak height as well as a variation in the profile of band 3 were produced in controls by specific manipulations of the electrophoresis protocol. Metabolic depletion of normal cells produced the type of alterations in bands 3 and 4.1 found in xerocyte membranes, whereas Heinz body production, addition of calcium to the hemolysis buffer and incubation of membranes in detergent under conditions designed to promote proteolysis did not. The presence of a higher peak height of band 4.1b with respect to that of band 4.1a in membranes of patients with various other red cell disorders correlated with an increase in the percentage of reticulocytes in peripheral circulation. The appearance of both band 3 and 4.1 abnormalities in the patterns of control cells which had been enriched in young cells by density gradient centrifugation suggested that these alterations in hemolytic disease are related to the predominance of young cells in the population.

Abnormalities of erythrocyte membranes in biliary atresia: ultrastructure and lipid composition

Biochemical and ultrastructural studies of red blood cell membranes from seven patients with congenital biliary atresia have been performed. Scanning electron microscopic observations revealed that more than half of these cells were of abnormal shapes, such as target, spur and cup-formed cells. By freeze-fracture electron microscopy, membrane particle-free smooth areas were noted in the fracture faces. In addition, the number of membrane-associated particles was 20% less than those in control subjects. The lipid analysis of red blood cells showed a significant increase in phospholipid and a marked increase in cholesterol content. The increase of phospholipid content was primarily caused by the increase of lecithin. The acyl chain analysis of erythrocyte lecithin demonstrated an increase in palmitic, palmitoleic and oleic acid, and a decrease in stearic and linoleic acid. These observations are similar to those of acquired biliary obstruction. The fluidity of erythrocyte membrane lipid, studied by a fluorescence technique using fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH), was found to be less in an individual with congenital biliary atresia than in the control subject.

Biochemical studies on abnormal erythrocyte membranes. Protein abnormality of erythrocyte membrane in biliary obstruction

Biochemical studies on erythrocyte membranes from eleven obstructive jaundice patients (due to various disorders) have been undertaken, By scanning electron microscopic observation these erythrocytes were spur and target in appearance. The lipid composition showed a marked increase in both cholesterol and phosphatidylcholine. In addition to these changes, it was unexpectedly demonstrated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate that a specific membrane protein component 4.2 was reduced or absent in all cases tested. This membrane protein abnormality was identical with that of hereditary spherocytosis erythrocyte membranes. It is of particular interest to note that after surgical relief of biliary obstruction in a typical case of common duct cholelithiasis, the disc electrophoretic pattern of erythrocyte membranes became normal and both lipid composition and red cell morphology returned to normal.

Isoelectric focusing of spectrin components in hereditary spherocytosis

1. By isoelectric focusing in 8 M urea, spectrin purified from normal human erythrocytes was resolved into 12 to 15 peptide bands differing by their isoelectric point. Most of them were focused between pH 6.4 and 5.2, one at pH 8.7 and some minor components between pH 7.4 and 6.8. 2. The results were not influenced by the erythrocyte population age. 3. Spectrin purified from erythrocytes of five patients with hereditary spherocytosis gave similar isoelectric focusing patterns, with the exception of the lack of the pH 8.7-focused component in two related patients.

Elevated microviscosity in membranes of erythrocytes affected by hereditary spherocytosis

Erythrocytes affected by hereditary spherocytosis (HS), obtained from several splenectomized patients, showed a varying degree of elevated osmotic fragility. In order to evaluate a possible role of the erythrocyte membrane lipids in HS, microviscosity of the membrane lipid core was measured by a fluorescence-polarization technique. Intact HS-affected red cells, as well as their ghost membranes and liposomes prepared from their lipid extract, all showed a distinctly higher micro-viscosity than the respective normal control. The increased microviscosity correlated with the severity of HS. The data support the proposition that the defect in HS-affected red cells is associated, at least in part, with alterations in the membrane lipids.