Molecular cloning of human protein 4.2: a major component of the erythrocyte membrane

Erythrocyte membrane protein analysis by sodium dodecyl sulphate-capillary gel electrophoresis in the diagnosis of hereditary spherocytosis

BACKGROUND

Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) is currently the reference method for detecting protein deficiencies related to hereditary spherocytosis. The aim of the study was to evaluate an automated capillary gel electrophoresis system, the Experion instrument from BioRad, for its ability to separate and quantify the erythrocyte membrane proteins.

METHODS

The major erythrocyte membrane proteins (actin, protein 4.2, protein 4.1, band 3, ankyrin, α- and β-spectrin) were extracted and purified from membrane ghosts by centrifugation, immunoprecipitation and electroelution. Analyses were performed using SDS-PAGE and sodium dodecyl sulphate capillary gel electrophoresis (SDS-CGE) to establish a separation profile of the total ghosts. Then, the samples from patients received for investigations of erythrocyte membrane defects were analysed.

RESULTS

Five of the seven expected erythrocyte membrane proteins were finally separated and identified. In the 20 studied cases, taking into account the screening test results and the clinical and family histories, the SDS-CGE method allowed us to achieve the same conclusion as with SDS-PAGE, except for the patient with elliptocytosis.

CONCLUSIONS

The new SDS-CGE method presents interesting features that could make this instrument a powerful diagnostic tool for detection of erythrocyte membrane protein abnormalities, and can be proposed as an automated alternative method to the labour intensive SDS-PAGE analysis.

Interactions of Recombinant Mouse Erythrocyte Transglutaminase with Membrane Skeletal Proteins

Transglutaminases (TGs) are a family of enzymes that catalyze the formation of covalent gamma-glutamyl-epsilon-lysine crosslinks between glutamine (Q) acyl-donors and lysine (K) acyl-acceptors. Here, we report the cDNA cloning of a TG from mouse reticulocytes, its 4.6-kb message size and high-yield synthesis of recombinant TG in yeast cultures. Its activity was assayed by crosslinking the amine of monodansylcadaverine (DC) onto casein and inside-out vesicles of erythrocytes. The latter contain TG substrates including the anion ion exchanger (AE1) or band 3, and the crosslinking activity was the highest at physiological [GTP] and [ATP] of erythrocytes. To study individually how TG interacts with band 3 and what role P4.2, a pseudo-TG that is normally associated with band 3, may play in their interaction, recombinant cytoplasmic domain of band 3 (cdb3) and P4.2 were also cloned by polymerase chain reaction from mouse reticulocytes, expressed and affinity-purified from Escherichia coli. Enzyme-linked immunosorbent assay and Western blot analysis revealed that increasing [CaCl(2)] enhanced TG-mediated crosslinking of DC to cdb3 but decreased TG binding to cdb3. P4.2 inhibited the TG-mediated crosslinking of cdb3 but stabilized the binding of TG to cdb3 in the presence of calcium. This in vitro study suggests a relationship among TG, cdb3 and P4.2 in erythrocyte membrane during calcium influx.

Protein 4.2 Komatsu (D175Y) associated with the lack of interaction with ankyrin in human red blood cells

Membrane skeletal proteins play an important role in regulating the shape and function of the human red blood cell. Protein 4.2 interacts with cytoplasmic domain of band 3 (CDB3) and ankyrin for association between the skeleton network and the membrane. The deficiency of protein 4.2 may result in hereditary spherocytosis. In order to explore the molecular mechanism of the linkage of protein 4.2 Komatsu (D175Y) and protein 4.2 Nippon (A142T) with hereditary spherocytosis, a series of protein 4.2-derived mutants were designed and expressed in Escherichia coli. Their interactions with ankyrin and CDB3 were investigated by Far Western blot and pull-down assay in vitro. The results showed that the mutant D175Y of protein 4.2 cannot interact with ankyrin while mutant A142T, just like normal protein 4.2, can bind to ankyrin directly and can associate with CDB3 in the presence of ankyrin. Based on comparing the binding abilities of the protein 4.2 mutants D175F, D175A, D175K and D175Y with ankyrin and CDB3, we suggested that defective binding of protein 4.2 Komatsu to ankyrin is resulted from the charge effect of amino acid residue 175 substitution (D-->Y), which leads to significant structural change in protein 4.2 function domain.

Associations of protein 4.2 with band 3 and ankyrin

Protein-protein and protein-lipid interactions are thought to play the vital role in maintenance and deformation of red blood cell (RBC) membrane. Protein 4.2, a 76-KDa peripheral protein, binds to the cytoplasmic domain of band 3 (CDB3) and also interacts with ankyrin in RBCs. In order to explore the characteristics of protein 4.2-CDB3-ankyrin interactions, three protein 4.2-derived recombinant proteins encompassing amino acid residues 31-200, 1-300, and 187-260 respectively were expressed in Escherichia coli. Their interactions with CDB3 and ankyrin were investigated by using Far-Western blot and pull-down assay. The results showed that the CDB3-binding site of protein 4.2 is located in the region of residues 200-211 and the ankyrin-binding site is located in the region of residues 187-200 of protein 4.2. Our findings also suggested that the ankyrin D34 domain can interact directly with protein 4.2. The proper tertiary structures of these protein 4.2 fragments are essential for protein 4.2-ankyrin interaction. Meanwhile, ankyrin can enhance the interaction between protein 4.2 and CDB3.

Protein-4.2 association with band 3 (AE1, SLCA4) in Xenopus oocytes: effects of three natural protein-4.2 mutations associated with hemolytic anemia

We have investigated the effects of coexpression of protein 4.2 and three protein-4.2 variants with band 3 in the Xenopus oocyte expression system. Normal protein 4.2 increased band-3–specific chloride transport in the oocytes. Protein 4.2 also coimmunoprecipitated with band 3 and colocalized with band 3 at the oocyte plasma membrane. The increase in band-3–mediated chloride transport and coimmunoprecipitation of protein 4.2 required the presence of the N-terminal cytoplasmic domain of band 3. Protein 4.2 also localized to the oocyte plasma membrane in the absence of band 3. The protein-4.2 variants 4.2 Tozeur (R310Q) and 4.2 Komatsu (D175Y) had impaired ability to bind to band 3 and these variants did not localize to the oocyte plasma membrane when expressed on their own or when coexpressed with band 3. Unexpectedly, 4.2 Nippon (A142T) behaved similarly to normal protein 4.2. In the absence of a crystal structure of protein 4.2, we propose a homology model of protein 4.2 based on the structure of the sequence-related protein transglutaminase. Using our results in oocytes and this homology model we speculate how these mutations affect protein 4.2 and result in hereditary spherocytosis.

Mapping of a spectrin-binding domain of human erythrocyte membrane protein 4.2

Protein 4.2 is a major component of the red blood cell membrane skeleton. Deficiency of protein 4.2 is linked with a variety of hereditary haemolytic anaemias. However, the interactions of protein 4.2 with other proteins of the erythrocyte membrane remain poorly understood. The major membrane-binding site for protein 4.2 resides on the cytoplasmic domain of band 3. Protein 4.2 interacts directly with spectrin in solution, suggesting that it stabilizes interactions between the membrane skeleton and the erythrocyte membrane. A 30 kDa polypeptide, with its N-terminus corresponding to amino acid residue 269, derived by partial proteolysis of protein 4.2, was found to interact with biotinylated spectrin in gel renaturation assays. A series of overlapping glutathione S-transferase fusion peptides were constructed, and an alpha-helical domain encompassing residues 470-492 was found to be instrumental in mediating protein 4.2-spectrin interactions. Direct binding of a synthetic peptide, with the sequence corresponding to residues 470-492, to spectrin and the ability of the peptide to inhibit spectrin binding of protein 4.2 confirmed that these residues are crucial in mediating protein 4.2-spectrin interactions.

Site-directed mutagenesis of the calcium-binding site of blood coagulation factor XIIIa

Blood coagulation factor XIIIa is a calcium-dependent enzyme that covalently ligates fibrin molecules during blood coagulation. X-ray crystallography studies identified a major calcium-binding site involving Asp(438), Ala(457), Glu(485), and Glu(490). We mutated two glutamic acid residues (Glu(485) and Glu(490)) and three aspartic acid residues (Asp(472), Asp(476), and Asp(479)) that are in close proximity. Alanine substitution mutants of these residues were constructed, expressed, and purified from Escherichia coli. The K(act) values for calcium ions increased by 3-, 8-, and 21-fold for E485A, E490A, and E485A,E490A, respectively. In addition, susceptibility to proteolysis was increased by 4-, 9-, and 10-fold for E485A, E490A, and E485A,E490A, respectively. Aspartic acids 472, 476, and 479 are not involved directly in calcium binding since the K(act) values were not changed by mutagenesis. However, Asp(476) and Asp(479) are involved in regulating the conformation for exposure of the secondary thrombin cleavage site. This study provides biochemical evidence that Glu(485) and Glu(490) are Ca(2+)-binding ligands that regulate catalysis. The binding of calcium ion to this site protects the molecule from proteolysis. Furthermore, Asp(476) and Asp(479) play a role in modulating calcium-dependent conformational changes that cause factor XIIIa to switch from a protease-sensitive to a protease-resistant molecule.

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.

Mapping of a palmitoylatable band 3-binding domain of human erythrocyte membrane protein 4.2

Evidence accumulated over the years suggests that human erythrocyte membrane protein 4.2 is one of the proteins involved in strengthening the cytoskeleton-membrane interactions in the red blood cell. Deficiency of protein 4.2 is linked with a variety of hereditary haemolytic anaemia. However, the interactions of protein 4.2 with other proteins of the erythrocyte membrane remain poorly understood. The major membrane-binding site for protein 4.2 resides on the cytoplasmic domain of band 3 (CDB3). In order to carry out an initial characterization of its interaction with the CDB3, protein 4. 2 was subjected to proteolytic cleavage and gel renaturation assay, and the 23-kDa N-terminal domain was found to interact with band 3. This domain contained two putative palmitoylatable cysteine residues, of which cysteine 203 was identified as the palmitoylatable cysteine. Recombinant glutathione S-transferase-fusion peptides derived from this domain were characterized with respect to their ability to interact with the CDB3. Whereas these studies do not rule out the involvement of other subsites on protein 4.2 in interaction with the CDB3, the evidence suggests that the region encompassing amino acid residues 187-211 is one of the domains critical for the protein 4.2-CDB3 interaction. This is also the first demonstration that palmitoylation serves as a positive modulator of this interaction.

Molecular basis of bovine red-cell protein 4.2 polymorphism in Japanese black cattle

Cattle were divided into three groups according to the red cell-protein 4.2 (P4.2) phenotypes P4.2(76), P4.2(75) and P4. 2(76/75), whose red cells contained Mr 76000 (P4.2/76), 75000 (P4. 2/75) and both 76000 and 75000 isoforms respectively. To elucidate the molecular basis that underlies the diversity of P4.2, the gene structures of bovine P4.2/76 and P4.2/75 were investigated. Two P4.2 cDNA clones were isolated from bone-marrow cDNAs of the animal with the P4.2(76/75) phenotype. These were identical in size (2.2 kb), encoding major erythroid P4.2 with 687 amino acids, but were different in three nucleotides, resulting in changes of amino acids at the 599th, 601st and 627th residues. Analysis of genomic DNA from the three phenotypes demonstrated that these two clones were derived from gene transcripts by which P4.2/76 and/or P4.2/75 were produced. In vitro transcription and translation of P4.2/76 and P4.2/75 cDNAs indeed generated P4.2/76 and P4.2/75 identical in size to the red-cell proteins. These findings demonstrated that polymorphism of the P4.2 gene at codons 599, 601 and 627 of P4.2 cDNA was the cause of the molecular diversity of bovine red-cell P4.2. Although distinct electrophoretic mobilities suggested a structural difference in the two isoforms, this polymorphism appeared to have little effect at least on P4.2 association with band 3, since no significant difference was observed in the amount of P4.2 relative to total membrane proteins despite the phenotype difference for P4.2.

Developmental Expression of Mouse Erythrocyte Protein 4.2 mRNA: Evidence for Specific Expression in Erythroid Cells

Erythrocyte protein 4.2 (P4.2) is an important component of the erythrocyte membrane skeletal network with an undefined biologic function. Presently, very little is known about the expression of the P4.2 gene during mouse embryonic development and in adult animals. By using the Northern blot and in situ hybridization techniques, we have examined the spatial and temporal expression of the P4.2 gene during mouse development. We show that expression of the mouse P4.2 gene is temporally regulated during embryogenesis and that the P4.2 mRNA expression pattern coincides with the timing of erythropoietic activity in hematopoietic organs. P4.2 transcripts are first detected in embryos on day 7.5 of gestation and are localized exclusively in primitive erythroid cells of yolk sac origin. These erythroid cells remain to be the only source for P4.2 expression until the switch of the hematopoietic producing site to fetal liver. In mid- and late-gestation periods, P4.2 mRNA expression is restricted to the erythroid cells in fetal liver and to circulating erythrocytes. Around and after birth, the site for P4.2 expression is switched from liver to spleen and bone marrow, and P4.2 transcripts are only detected in cells of the erythroid lineage. These results provide the evidence for specific P4.2 expression in erythroid cells. In addition, the timing and pattern of expression of the P4.2 gene suggest the specific regulation of the P4.2 gene.

Developmental Expression of Mouse Erythrocyte Protein 4.2 mRNA: Evidence for Specific Expression in Erythroid Cells

Erythrocyte protein 4.2 (P4.2) is an important component of the erythrocyte membrane skeletal network with an undefined biologic function. Presently, very little is known about the expression of the P4.2 gene during mouse embryonic development and in adult animals. By using the Northern blot and in situ hybridization techniques, we have examined the spatial and temporal expression of the P4.2 gene during mouse development. We show that expression of the mouse P4.2 gene is temporally regulated during embryogenesis and that the P4.2 mRNA expression pattern coincides with the timing of erythropoietic activity in hematopoietic organs. P4.2 transcripts are first detected in embryos on day 7.5 of gestation and are localized exclusively in primitive erythroid cells of yolk sac origin. These erythroid cells remain to be the only source for P4.2 expression until the switch of the hematopoietic producing site to fetal liver. In mid- and late-gestation periods, P4.2 mRNA expression is restricted to the erythroid cells in fetal liver and to circulating erythrocytes. Around and after birth, the site for P4.2 expression is switched from liver to spleen and bone marrow, and P4.2 transcripts are only detected in cells of the erythroid lineage. These results provide the evidence for specific P4.2 expression in erythroid cells. In addition, the timing and pattern of expression of the P4.2 gene suggest the specific regulation of the P4.2 gene.

A new transglutaminase-like from the ascidian Ciona intestinalis

A cDNA clone encoding a transglutaminase (TGase) was isolated from a cDNA library prepared from the larval stage of Ciona intestinalis. The cDNA sequence has an open reading frame encoding a protein of 696 amino acids and is about 36% identical to 11 other TGase sequences. In addition, the critical residues thought to form the catalytic center are conserved. The Ciona TGase (CiTGase) has an extension of 39 amino acids in the NH2-terminal region similar to that reported for keratinocyte TGases. A phylogenetic analysis among other types of TGases demonstrated that CiTGase represents a new type of the enzyme.

Association of a transglutaminase-related antigen with intermediate filaments

A mouse monoclonal antibody, G92.1.2, raised against guinea pig liver transglutaminase (TGase) recognizes an antigen present in primary mouse dermal fibroblasts. A filamentous pattern, bearing remarkable similarity to the vimentin intermediate filament (IF) network, is seen when these cells are fixed and processed for indirect immunofluorescence with the antibody. Double-label immunofluorescence reveals that the antigen reacting with the antibody colocalizes precisely with vimentin IF and that this colocalization is retained after the treatment of fibroblasts with colchicine, which induces a redistribution of the majority of IFs into perinuclear aggregates. These morphological observations are further supported by the finding that the protein reacting with G92.1.2 is retained in IF-enriched cytoskeletal preparations made by using nonionic detergent-containing high ionic strength solutions. Western blots of the IF fraction show that G92.1.2 recognizes a major band of approximately 280 kDa and does not cross react with vimentin. Furthermore, when the antibody is microinjected into live dermal fibroblasts, it causes a collapse of the vimentin IF network in the majority of injected cells. The results suggest that a form of TGase, or a TGase-related antigen, is closely associated with the vimentin IF network of primary cultures of mouse dermal fibroblasts.

Identification of a band-3 binding site near the N-terminus of erythrocyte membrane protein 4.2

Protein 4.2 (P4.2) is a major component of the erythrocyte plasma membrane accounting for approx. 5% of total membrane protein. The major membrane binding site for P4.2 is contained within the cytoplasmic domain of band 3 (cdb3), although the precise location of the cdb3 binding site is not known. To identify the cdb3 binding site, we used synthetic P4.2 peptides (15-mers) that spanned the entire 721-amino-acid large isoform of P4.2, and determined the binding of these peptides to cdb3 in an in vitro binding assay. One peptide, P8 (L61FVRRGQPFTIILYF), bound strongly to cdb3 and four others bound less strongly (P22, L271LNKRRGSVPILRQW; P27, G346EGQRGRIWIFQTST; P41, L556WRKKLHLTLSANLE; P48, I661HRERSYRFRSVWPE). These peptides have in common a cluster of two or three basic amino acid residues (arginine or lysine), in a region without nearby acidic residues. Cdb3 bound saturably to P8 with a Kd of 0.16 microM and a capacity of 0.56 mol of cdb3 monomer/mol of P8. Use of overlapping synthetic peptides further defined the cdb3 site as being contained within V63RRGQPFTIILYF. Replacement of R64R with R64G, G64R or G64G almost completely abolished cdb3 binding, suggesting that R64R is essential for cdb3 binding. P8 competitively inhibited binding of purified human erythrocyte P4.2 to cdb3. In blot overlay assays, cdb3 bound to a 23 kDa N-terminal P4.2 tryptic peptide containing V63RRGQPFTIILYF but not to other P4.2 tryptic peptides lacking this site. The V63RRGQPFTIILYF site is highly conserved in mouse and human erythrocyte P4.2 as well as between P4.2 and transglutaminase proteins, which are evolutionarily related to P4.2.

A point mutation in the protein 4.2 gene (allele 4.2 Tozeur) associated with hereditary haemolytic anaemia

A recessively transmitted haemolytic anaemia associated with the lack of protein 4.2 was found in a Tunisian kindred. Trace amounts of this protein (72 kD component) became visible using high-sensitivity Western blots. Band 3 and ankyrin genes were excluded as candidate genes by linkage studies, and nucleotide sequencing of band 3 cytoplasmic domain cDNA revealed no alteration. In contrast, protein 4.2 gene contained in the homozygous state a mutation at position 310: CGA-->CAA (Arg-->Gln). This mutation defining allele 4.2 Tozeur was co-inherited with the disease. The mRNA encoding the variant protein was normal in size and approximately normal in amount. Recombinant protein 4.2 Tozeur bound normally to red cell IOVs but disclosed an increased susceptibility to proteolysis in vitro. We infer that the nearly total absence of protein 4.2 in the patients results from imbalance between destruction and synthesis of mutated protein 4.2 prior to its binding to the membrane.

Expression of tissue-type transglutaminase correlates positively with metastatic properties of human melanoma cell lines

In this study the relationship between tissue-type transglutaminase (TGase2) activity and the propensity to metastasize was investigated in human melanoma cell lines with different metastatic behavior. TGase2 catalyzes an acyl-transfer reaction between peptide-bound glutamine residues and primary amines, including the epsilon-amino group of lysine residues. Northern-blot analysis demonstrated that TGase2 RNA-expression (3.7 kb) was elevated in highly metastatic cell lines (MV3 and BLM) as compared to weakly metastatic ones (IF6 and 530). Immunoprecipitation and enzyme assays of TGase2 showed that the differential expression at the mRNA level was also reflected at the protein level. These findings reveal a positive relation between the expression of TGase2 and the metastatic properties of the human melanoma cell lines.

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.

Human erythrocyte membrane protein 4.2 is palmitoylated

Protein 4.2 is a major protein of the human erythrocyte membrane. It has previously been shown to be N-myristoylated. After labeling of intact human erythrocytes with [3H]palmitic acid, radioactivity was found to be associated with protein 4.2 by immunoprecipitation of peripheral membrane proteins extracted at pH 11 from ghosts with anti-(4.2) sera, followed by SDS/PAGE and fluorography. The fatty acid linked to protein 4.2 was identified as palmitic acid after hydrolysis of protein and thin-layer chromatography of the fatty acid extracted in the organic phase. Protein 4.2 could be depalmitoylated with hydroxylamine, suggesting a thioester linkage. Depalmitoylated protein 4.2 showed significantly decreased binding to protein-4.2-depleted membranes, compared to native protein 4.2.

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.

Cellular transglutaminases in neural development

Enzymes of the transglutaminase family catalyze the Ca(2+)-dependent covalent cross-linking of peptide-bound glutamine residues of proteins and glycoproteins to the epsilon-amino group of lysine residues to create inter- or intramolecular isopeptide bonds. Transglutaminases can also covalently link a variety of primary amines to peptide-bound glutamine residues giving rise to two possibilities; firstly, where the primary amine has two or more amino groups, further catalysis can result in the formation of cross-linked bridges between glutamine residues, and secondly, where the primary amine is a monoamine, glutamine residues are rendered inert to further modification. The products are therefore in the main, homo- or heterodimers, or extensive, metabolically-stable multimeric complexes or matrices. Ca(2+)-dependent transglutaminase activity is present in the mammalian peripheral and central nervous systems and transglutaminase-catalyzed cross-linking of endogenous substrates has been demonstrated in neurons of Aplysia and the mammalian brain. Transglutaminase activity increases in the brain during development, principally owing to the increasing preponderance of glial cell activity. In a few regions including the cerebellar cortex, activity is also high in early development. Cellular transglutaminases occur widely in differentiating cells and tissues in mammals, with more than one transglutaminase frequently associated with a single cell type. The primary protein sequences of three cellular transglutaminases have been fully determined in different species, together with that of a mammalian protein homologue (band 4.2) which shares extensive sequence homologies with transglutaminases, but lacks the active site cysteine residue. The upstream sequences of two mammalian cellular transglutaminase genes (C and K) contain numerous regulatory sites, and an invertebrate transglutaminase, annulin, is spatially regulated within homeodomains. Multiple molecular forms of transglutaminase C and possibly other cellular transglutaminases exist in mammalian brain. The emerging picture is one of a family of cytosolic and membrane-bound proteins central to several regulatory pathways whose functions is to stabilize the cellular and intercellular superstructure in growing organisms. The targeted formation of glu-lys isopeptide bonds between proteins is central to this function. Cytoskeletal proteins, membrane-associated receptors, enzymes in signal transduction pathways and extracellular glycoproteins are candidate substrates as are polyamines, but few cellular proteins have been identified as components of naturally-occurring covalently-bonded matrices. Transglutaminases participate in the programme of neuronal differentiation in some but not all classes of neurone. Both neuronal and non-neuronal expression of transglutaminases may be important for guidance of migrating neurons or growth cones and sustainment of cell shape and coordinates during development.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

An isoform-specific mutation in the protein 4.1 gene results in hereditary elliptocytosis and complete deficiency of protein 4.1 in erythrocytes but not in nonerythroid cells

Multiple protein 4.1 isoforms are expressed in a variety of tissues through complex alternative pre-mRNA splicing events, one function of which is to regulate use of two alternative translation initiation signals. Late erythroid cells express mainly the downstream initiation site for synthesis of prototypical 80-kD isoforms; nonerythroid cells in addition use an upstream site to encode higher molecular mass isoform(s). In this study, we examined the effects of a 5' gene rearrangement in a family with hereditary elliptocytosis and complete deficiency of erythrocyte 4.1 protein on 4.1 isoform expression in erythroid vs. nonerythroid cells. Patient 4.1 mRNAs from reticulocytes, fibroblasts, and B lymphocytes were amplified by reverse transcriptase/polymerase chain reaction techniques and shown to exhibit a 318-nucleotide deletion that encompasses the downstream AUG, but leaves intact the upstream AUG. Immunoblot analysis revealed a total deficiency of 4.1 in patient red cells and a selective deficiency of 80-kD isoform(s) but not high molecular weight 4.1 in patient nonerythroid cells. Thus, the 4.1 gene mutation in this family produces an isoform-specific deficiency that is manifested clinically in tissue-specific fashion, such that red cells are affected but other cell types are unaffected because of tissue-specific differences in RNA splicing and translation initiation.

Cloning and expression of chicken erythrocyte transglutaminase

We report the sequences of cDNAs encoding chicken erythrocyte transglutaminase (EC 2.3.2.13). The complete mRNA consists of 3345/3349 nucleotides and predicts a single open reading frame. Nine peptide sequences derived from partial digests of the isolated protein agreed with the corresponding translation of the open reading frame. Approximately 60% identities between the avian protein and three related mammalian enzymes were found. Chicken erythrocyte transglutaminase mRNA is most abundant in red blood cells and kidney, and it accumulates during erythroid cell differentiation.

The murine pallid mutation is a platelet storage pool disease associated with the protein 4.2 (pallidin) gene

Pallid is one of 12 independent murine mutations with a prolonged bleeding time that are models for human platelet storage pool deficiencies in which several intracellular organelles are abnormal. We have mapped the murine gene for protein 4.2 (Epb4.2) to chromosome 2 where it co-localizes with pallid. Southern blot analyses suggest that pallid is a mutation in the Epb4.2 gene. Northern blot analyses demonstrate a smaller than normal Epb4.2 transcript in affected pallid tissues, such as kidney and skin. This is the first gene defect to be associated with a platelet storage pool deficiency, and may allow the identification of a novel structure or biological pathway that influences granulogenesis.

Organization and evolution of the human epidermal keratinocyte transglutaminase I gene

Transglutaminases (TGases; protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13) are calcium-dependent crosslinking enzymes that modify proteins posttranslationally. Several distinct types of TGases have been identified, which appear to be encoded by a family of closely related genes. We isolated the gene encoding human keratinocyte-specific type I TGase (TGase I) and characterized its chromosomal organization. The TGase I gene consists of 15 exons separated by 14 introns and exhibits a restriction fragment length polymorphism. Exons appear to encode functional and/or structural domains: exon I and part of exon XV encode untranslated regions, whereas exons VII and XI contain the active site and a presumptive calcium-binding domain, respectively. Interestingly, exon VI of TGase I contains a consensus Arg-Gly-Asp tripeptide sequence whose presence suggests an intriguing extracellular function for the enzyme. We present a likely phylogenetic tree for seven known members of the TGase family based on amino acid sequence similarity. Arguments presented suggest that the active enzyme evolved first and the structural human erythrocyte membrane protein 4.2 (band 4.2) has undergone a rapid change in amino acid sequence. It follows that band 4.2 evolved from the type II TGases, whereas factor XIII subunit a evolved from the type I group.

Characterization of the phosphorylated state of protein 4.2 from a patient partially deficient in protein 4.2

These studies compare the protein 4.2 found in a patient with osmotically fragile, spherocytic erythrocytes to the normal protein 4.2. The patient protein 4.2 is present in the erythrocyte ghost membranes as a doublet of 74 and 72 KDa at a concentration less than 1% of normal. The patient protein 4.2 becomes highly phosphorylated in the presence of Zn++ and is phosphorylated, relative to the amount of protein present, to a greater extent than the normal 72 KDa protein 4.2. These studies indicate that both the patient and the normal protein 4.2 usually exists in a highly phosphorylated state. The phosphorylation sites on the patient protein 4.2 appear to be more readily cycled than on the normal protein 4.2. Staphylococcus aureus V8 protease generates similar phosphopeptides in both the normal and patient protein 4.2 except for an extra 11 KDa phosphopeptide generated from the 74 KDa form of the protein.

The gene for human erythrocyte protein 4.2 maps to chromosome 15q15

Protein 4.2 (P4.2), one of the major components of the red-blood-cell membrane, is located on the interior surface, where it binds with high affinity to the cytoplasmic domain of band 3. Individuals whose red blood cells are deficient in P4.2 have osmotically fragile, abnormally shaped cells and moderate hemolytic anemia. cDNA clones from both the 5' and the 3' coding regions of the P4.2 gene were used to map its chromosomal location by fluorescence in situ hybridization. The probes, individually or in combination, gave specific hybridization signals on chromosome 15. The hybridization locus was identified by combining fluorescence images of the probe signals with fluorescence banding patterns generated by Alu-PCR (R-like) probe and by DAPI staining (G-like). Our results demonstrate that the locus of the P4.2 gene is located within 15q15.

Organization of the gene for human erythrocyte membrane protein 4.2: structural similarities with the gene for the a subunit of factor XIII

Human erythrocyte band 4.2 is a major membrane-associated protein with an important, but still undefined, role in erythrocyte survival. We previously sequenced the complete cDNA for band 4.2 and showed that the protein has a strong sequence identity with the transglutaminase family of proteins but lacks transglutaminase activity. Here we have analyzed the genomic organization of band 4.2. The band 4.2 gene is approximately 20 kilobases, consisting of 13 exons and 12 introns. Reticulocytes contain two different sized messages for band 4.2, and our results show that the major, smaller, message is produced by alternative splicing within band 4.2 exon I. The upstream region of the gene has several prospective promoter elements arranged in a pattern similar to that of two other erythroid genes, beta-globin and porphobilinogen deaminase. Alignment of the band 4.2 amino acid sequence with that of the a subunit of human coagulation factor XIII and division of the sequences into exons reveal a remarkable correspondence, and in most cases identity, in the sizes of the paired exons. Moreover, each corresponding intron of the two genes is of an identical splice junction class. These and other similarities suggest that the gene for band 4.2 is closely related to and possibly derived from that for the a subunit of factor XIII and that the proteins may share common structural and functional properties.

Primary structure of keratinocyte transglutaminase

The nucleotide and deduced amino acid sequences of the coding regions of human and rat keratinocyte transglutaminases (protein-glutamine: amine gamma-glutamyltransferase; EC 2.3.2.13) have been determined. These yield proteins of approximately 90 kDa that are 92% identical, indicative of the conservation of important structural features. Alignments of amino acid sequences show substantial similarity among the keratinocyte transglutaminase, human clotting factor XIII catalytic subunit, guinea pig liver tissue transglutaminase, and the human erythrocyte band-4.2 protein. The keratinocyte enzyme is most similar to factor XIII, whereas the band-4.2 protein is most similar to the tissue transglutaminase. A salient feature of the keratinocyte transglutaminase is its 105-residue extension beyond the N terminus of the tissue transglutaminase. This extension and the unrelated activation peptide of factor XIII (a 37-residue extension) appear to be added for specialized functions after divergence of the tissue transglutaminase from their common lineage.

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.