Molecular Basis of Tn-Polyagglutinability

Andreu

European Journal of Biochemistry

et al. 1978

105

The serum and red cell membranes from seven Tn individuals have been tentatively characterized for the U DPgalactose : ~~-acety~-D-ga~actosamine-~-D-ga~actosy~transferase and UDPgalactose : 2'-ncetyl-~-glucosamine-~-4-~-galactosyltransferase activities using p-Nitrophenyl-2-acetamido-2-deoxy-a-D-galactopyranoside and p-N~trophenyl-2-acetamido-2-deoxy-~-~-glucopyranos~de respectively as low molecular weight acceptors. In five cases, Tn-positive and Tn-negative red cells were at first separated by Polybrene differential aggregation. The following conclusions have been drawn.1. The p-3-D and 8-4-D-galactosyltransferases activities are found in serum and red cell membranes from all normal individuals.2. Polybrene-positive cells (normal sialic acid content) from Tn bloods have either normal or higher 8-3-D and ~-4-~-galactosyltransferase activities.3. Polybrene-negative cells (low sialic acid content) from Tn bloods have a selective deficiency in P-3-~-galactosyltransferase (T-transferase) activity, but normal or even increased P-4-~-galactosyltransferase activity.4. The serum from all Tn individuals behaves like normal sera in respect of the two galactosyltransferase activities. The serum may also be used as source of enzyme for conversion in vitro of Tn to T-reactive erythrocytes.The above data strongly support the view that Tn-polyagglutination results from a somatic mutation in stem cells of haematopoietic tissue which involves a single genetic step in red cell glycoprotein synthesis. It also provides further evidence of a dual population of erythrocytes in each Tn blood sample and suggests that T-transferase found in serum is produced in unidentified cells of the organism. No difference has been noticed between apparently healthy Tn donors and Tn patients.Polyagglutinable erythrocytes are agglutinated by many sera, irrespective of blood group [l]. The phenomenon arises either by acquisition of extrinsic antigen or by uncovering of receptors, normallyAbbreviations. UDP-Gal, uridine diphospho-D-galactose; Npha-GalNAc, p-nitrophenyl-2-acetam~do-2-deoxy-a-~-galactopyranoside; Nph-P-GlcNAc: p-nitrophenyl-2-acetamido-2-deoxy-~-~-glucopyranoside; NaCl/Pi, phosphate-buffered saline (9 vol. 0.9 % NaCl + 1 vol. isotonic phosphate buffer pH 7

“…The curve given in Fig. 1 reduced mobility corresponding to a mean sialic acid loss of 50 -60 % [9,12,24,27]. According to the above results (Fig.…”

Section: Erythrocyte Charge and Polybrene Aggregationsupporting

confidence: 52%

Section: Polyacrylamide Gel Electrophoresismentioning

confidence: 81%

See 1 more Smart Citation

Demonstration of T‐Transferase Deficiency in Tn‐Polyagglutinable Blood Samples

Andreu

European Journal of Biochemistry

et al. 1978

105

“…Tn syndrome or permanent mixed-field polyagglutinability (PMFP)' is a human disorder characterized by the exposure of truncated 0-glycans, in particular the Tn antigen (GalNAca 1-O-Ser/Thr) (1) due to a selective deficiency of UDP-Gal:GalNAca l-O-Ser/Thr #1-3 galactosyltransferase (f3Gal-T) activ-ity (2, 3) in a variable proportion of hematopoietic cells (4). These patients, who are also said to have blood group Tn (5), occasionally develop hemolytic anemia, thrombopenia, and leukopenia most likely mediated by anti-Tn natural antibodies present in normal serum (6).…”

Section: Introductionmentioning

confidence: 99%

Persistent repression of a functional allele can be responsible for galactosyltransferase deficiency in Tn syndrome.

Thurnher¹,

Rusconi²,

Berger³

1993

J. Clin. Invest.

A human hematopoietic disorder designated as Tn syndrome or permanent mixed-field polyagglutinability has been ascribed to a stem cell mutation leading to a specific deficiency of UDP-Gal:GalNAcal-O-Ser/Thr #1-3 galactosyltransferase (#3Gal-T) activity in affected cells. To test for the possibility that an allele of the ,3Gal-T gene might be repressed instead of mutated, we have investigated whether 5-azacytidine or sodium n-butyrate, both inducers of gene expression, would reactivate expression of #3Gal-T in cloned enzyme-deficient T cells derived from a patient affected by the Tn syndrome. Flow cytometry revealed that a single treatment induced de novo expression of the Thomsen-Friedenreich antigen (Gal,61-3GalNAc-R), the product of 63Gal-T activity. In addition, a sialylated epitope on CD43 (leukosialin), which is present on normal but not on ,3Gal-T-deficient T cells, was also reexpressed. Although no #3Gal-T activity was detectable in untreated Tn syndrome T cells, after exposure to 5-azaC, #3Gal-T activity reached nearly normal values. Both agents failed to reactivate ,63Gal-T in Jurkat T leukemic cells, which also lack #3Gal-T activity. These data demonstrate that Tn syndrome T cells contain an intact B83Gal-T gene copy and that the enzyme deficiency in this patient is due to a persistent and complete but reversible repression of a functional allele. In contrast, the cause of 03Gal-T deficiency appears to be different in Jurkat T cells. (J. Clin.

European Journal of Biochemistry

“…Sialic acid, protein and sodium dodecylsulfate/polyacrylamide gel electrophoretic analyses were performed by the methods of Warren [23], Lowry et al [24] and Laemmli [22,25], respectively. Amino acids and amino sugars were determined on automated amino acid analyzers [18,20].…”

Section: Analytical Proceduresmentioning

confidence: 99%

Structural analysis of the Ss sialoglycoprotein specific for Henshaw blood group from human erythrocyte membranes

Dahr

Kordowicz

Judd

et al. 1984

The N-terminal structures of the MN and Ss erythrocyte membrane sialoglycoproteins (glycophorins A, B) from two Henshaw (He) blood-group heterozygotes were determined by manual sequencing of tryptic glycopeptides and various secondary fragments. No structural alteration of the M N glycoprotein co+uld be de+tected. The He-specific portion of the Ss glycoprotein was found to exhibit the N-terminal sequence Trp-Ser-Thr-Ser-Gly-(+ = glycosylation). Thus it differs at three positions from its normal counterpart which possesses 'N' activity and exhibits the N-terminal structure Leu-Sir-Thr-Thr-Glu-. Analysis of the Ss glycoprotein from 15 He-negative erythrocyte samples did not reveal any of the three He-specific structural alterations. The presence of a glycine residue at the fifth position of the blood-group-M-active M N glycoprotein as well as in the He-specific Ss glycoprotein provides an explanation for the occurence of antisera (anti-Me) reacting with the M and He antigens. + +Previous studies have provided evidence that the human MN and Ss blood-group gene loci encode the amino acid sequences of two (MN and Ss) sialoglycoproteins (SGPs) (synonyms : glycophorins A, B) in red blood cell membranes [I -41. Amino acid polymorphisms at the first (serinejleucine) and fifth (glycine/glutamic acid) positions of the major (MN) SGP determine M N blood-group specificity [5 -101, whereas the Ss antigens appear to be dependent on a methioninel threonine polymorphism at position 29 of the Ss SGP [ l l -131. The N-terminal 26 residues of the Ss SGP are identical with those of the blood-group-N-active major glycoprotein [9 -121. Therefore, the former molecule carries an additional N receptor, denoted as 'N' [1,3].The Henshaw (He) erythrocyte antigen, which occurs in about 5% of blacks and only rather rarely in Caucasians, is genetically associated with the MNSs receptors [ l , 14 -171. Serological studies have revealed that certain rabbit or human antisera, denoted as anti-Me, react with the He and M antigens, suggesting that both receptors exhibit a structural similarity. In the present communication we describe studies on the SGPs from two He heterozygotes. Our data demAbbreviations. BNPS-skatole, 2-(2-nitrophenylsulfenyl)-3-methyl-3-bromoindolenine; dansyl-, l-(dimethylamino)naphthalene-5-sulphonyl-; DABITC, 4-N,N-dimethylaminoazobenzene-4'-isothiocyanate; DABTH, 4-N,N-dimethylaminoazobenzene-4'-thiohydantoin; PITC, phenylisothiocyanate; SGP, sialoglycoprotein. Peptides are designated according to the SGP (MN or Ss) from which they were derived by trypsin (T), chymotrypsin (C), V8 protease (V) (after desialylation (d)) or cyanogen bromide (B) treatment, the elution during gel filtration (1 etc.) (EC 3.4.21.19). [3,7 -9,31,12,18 -221. Analytical proceduresSialic acid, protein and sodium dodecylsulfate/polyacrylamide gel electrophoretic analyses were performed by the methods of Warren [23], Lowry et al. [24] and Laemmli [22,25], respectively. Amino acids and amino sugars were determined on automated amino acid analyzers [...