Possible role of ABO system in age-related diseases and longevity: a narrative review

ABO blood group antigens are expressed either on the surface of red blood cells either on a variety of other cells. Based on the available knowledge of the genes involved in their biosynthesis and their tissue distribution, their polymorphism has been suggested to provide intraspecies diversity allowing to cope with diverse and rapidly evolving pathogens. Accordingly, the different prevalence of ABO group genotypes among the populations has been demonstrated to be driven by malaria selection. In the similar manner, a particular ABO blood group may contribute to favour life-extension via biological mechanisms important for surviving or eluding serious disease. In this review, we will suggest the possible association of ABO group with age-related diseases and longevity taking into account the biological role of the ABO glycosyltransferases on some inflammatory mediators as adhesion molecules.     

Consequences of the expression of sialylated antigens in breast cancer

Changes in cell surface glycosylation are common modifications that occur during oncogenesis, leading to the over-expression of tumour-associated carbohydrate antigens (TACA). Most of these antigens are sialylated and the increase of sialylation is a well-known feature of transformed cells. In breast cancer, expression of TACA such as sialyl-Lewis^x or sialyl-Tn is usually associated with a poor prognosis and a decreased overall survival of patients. However, the specific role of these sialylated antigens in breast tumour development and aggressiveness is not clearly understood. These glycosylation changes result from the modification of the expression of genes encoding specific glycosyltransferases involved in glycan biosynthesis and the level of expression of sialyltransferase genes has been proposed to be a prognostic marker for the follow-up of breast cancer patients. Several human cellular models have been developed in order to explain the mechanisms by which carbohydrate antigens can reinforce breast cancer progression and aggressiveness. TACA expression is associated with changes in cell adhesion, migration, proliferation and tumour growth. In addition, recent data on glycolipid biosynthesis indicate an important role of G_D3 synthase expression in breast cancer progression. The aim of this review is to summarize our current knowledge of sialylation changes that occur in breast cancer and to describe the cellular models developed to analyze the consequences of these changes on disease progression and aggressiveness.     

Identification and genetic regulation of the chalcone synthase multigene family in pea.

Chalcone synthase (CHS) is a key enzyme in the biosynthesis of diverse flavonoids involved in disease resistance, nodulation, and pigmentation in pea. We describe a multigene family encoding CHS and the effects of two regulatory loci, a and a2, on the pattern of expression of three of its member genes. Two of the genes, CHS1 and CHS3, are expressed in both petal and root tissue, whereas expression of a third gene, CHS2, is detected only in roots. The products encoded by the a and a2 loci are required for the expression of the CHS1 gene and for wild-type levels of expression of the CHS3 gene in petal tissue. In root tissue, all three CHS genes are expressed and induced by CuCl2 regardless of the genotype at the a and a2 loci. These results show that the various members of the CHS multigene family interact in diverse ways with multiple genetic signals in the plant, providing a basis for the differential expression of these genes. Spatially specific genetic regulation of distinct members of a multigene family has been clearly demonstrated.     

Histochemical and cytochemical localization of blood group antigens.

The oligosaccharide structures of blood group antigens are not the primary gene products; they are constructed in a stepwise manner by adding particular sugar to precursor oligosaccharides via several glycosyltransferases coded for by different blood group genes (Watkins 1966, 1978, 1980). Consequently, final profiles of antigens expressed in each cell type are influenced by many different factors such as the intrinsic composition of glycosyltransferase species which are defined by the genotype of the individuals, relative activity or amount of these enzymes (repression, derepression or induction of the enzymes), competition between enzymes with overlapping substrate specificity, the organization of the enzymes in membranes, utilizability of precursors and specific substrate sugars, and the activity level of degradating enzymes. Changes in the antigen profiles during maturation, differentiation and malignant transformation are thought to be intimately related to the variability of these factors. Although great importance attaches to histo- and cytochemical information on the distribution and levels of glycosyltransferases and messenger RNA corresponding to the relevant enzyme, detailed and precise localization of the blood group antigens and their variants is the base line for analyzing these complex factors. On the basis of individual genotype and histochemical findings about the antigen distribution and the interrelationship between cells and cellular components producing different antigenic structures (cellular and subcellular mosaicism), we can deduce precursor oligosaccharide levels as well as the status of gene activation and its primary product, glycosyltransferases. Thus, these findings are a prerequisite for further analysis at the molecular genetic level. As emphasized in this article, lectin staining or immunostaining methods with MAbs combined with glycosidase digestion procedures are powerful tools for in situ analysis of carbohydrate structures in histochemical systems. Although in some cases valuable results have been obtained by applying the technique, our knowledge concerning the distribution of complex carbohydrate structures is still far from satisfactory. Along with well defined MAbs and lectins, the key to developing our methods further is successful introduction of glycosidases, in particular, endoglycosidases since these reagents are indispensable for analyzing the inner core structures and glycoconjugate species of the blood group antigens. Application of these techniques at the ultrastructural level is an alluring possibility, even though many difficulties must be overcome. Although their functional roles have not yet been determined, a diverse array of macromolecules is known to be decorated with blood group-related antigens.(ABSTRACT TRUNCATED AT 400 WORDS)     

Occurrence and specificities of alpha 3-fucosyltransferases.

Summary The Le^x (CD15) carbohydrate antigen and sialylated and oligomeric derivatives thereof have been implicated in cell adhesion processes. Expression of these antigens is developmentally regulated and (re)occurrence of several members of this group has been reported in malignant transformation of cells. Studies on the enzymology and genetics of 3-fucosyltransferases, glycosyltransferases that play a key role in the biosynthesis of these antigens, would yield insight in the regulation of expression of these carbohydrate structures. In this paper the existing literature on these enzymes is reviewed and placed in the context of cell adhesion and malignancy.     

ABO blood group system

The ABO blood group system in humans has three different carbohydrate antigens named A, B, and O. The A antigen sequence is terminal trisaccharide N-acetylgalactosamine (GalNAc)α1-3[Fucα1-2]Galβ-, B is terminal trisaccharide Galα1-3[Fucα1-2]Galβ-, and O is terminal disaccharide Fucα1-2Galβ-. The single ABO gene locus has three alleles types A, B and O. The A and B genes code A and B glycosyltransferases respectively and O encodes an inactive enzyme. A large allelic diversity has been found for A and B transferases resulting in the genetic subgrouping of each ABO blood type. Genes for both transferases have been cloned and the 3D structure of enzymes with and without substrate has been revealed by NMR and X ray crystallography. The ABO blood group system plays a vital role in transfusion, organ and tissue transplantation, as well as in cellular or molecular therapies.     

Human chromosome 11 carries at least four genes controlling expression of cell-surface antigens

We have mapped two new genes to chromosome 11 which control the cell-surface expression of two distinct antigens defined by monoclonal antibodies. One of the antigens has a general tissue distribution and is associated with a molecular complex of two polypeptides of 80,000 dalton and 40,000 dalton molecular weight. The second antigen has a restricted tissue distribution and is carried on a polypeptide of 100,000 daltons. We have used a combination of genetic and biochemical techniques to demonstrate that these new markers are distinct from the antigens defined by the monoclonal antibodies F10.44.2 and W6/34 which are also encoded by genes on chromosome 11. It is concluded that human chromosome 11 carries at least four distinct genes controlling cell-surface antigen expression.     

Coordinated expression of clustered cancer/testis genes encoded in a large inverted repeat DNA structure

Cancer/testis antigens (CTA) are expressed in cancers and testis or placenta only and, therefore are considered promising targets for cancer immunotherapy and diagnosis. One family of CTA is the MAGEA family which comprises 13 members and was shown to be expressed synchronously with members from the CSAG (TRAG-3) family of CTA. The MAGEA genes are arranged in 4 subclusters located on the X chromosome. Subcluster III exposes a remarkable gene organization with an inverted repeat (IR) DNA structure of a triplicated couplet of a MAGEA gene and a CSAG gene. Analyzing the mRNA expression pattern of all genes of the MAGEA and CSAG family of cancer/testis genes, we show that the MAGEA and CSAG genes encoded in the large IR are expressed coordinately and independent from the MAGEAs encoded outside the IR. These results reinforce our hypothesis that the large MAGEA/CSAG-IR DNA structure has an impact on the regulation of gene expression.     

Donor substrate specificity of recombinant human blood group A, B and hybrid A/B glycosyltransferases expressed in Escherichia coli.

The human blood group A and B glycosyltransferases catalyze the transfer of GalNAc and Gal, to the (O)H-precursor structure Fuc alpha (1-2)Gal beta-OR to form the blood group A and B antigens, respectively. Changing four amino acids (176, 235, 266 and 268) alters the specificity from an A to a B glycosyltransferase. A series of hybrid blood group A/B glycosyltransferases were produced by interchanging these four amino acids in synthetic genes coding for soluble forms of the enzymes and expressed in Escherichia coli. The purified hybrid glycosyltransferases were characterized by two-substrate enzyme kinetic analysis using both UDP-GalNAc and UDP-Gal donor substrates. The A and B glycosyltransferases were screened with other donor substrates and found to also utilize the unnatural donors UDP-GlcNAc and UDP-Glc, respectively. The kinetic data demonstrate the importance of a single amino acid (266) in determining the A vs. B donor specificity.     

Analysis of lipooligosaccharide biosynthesis in the Neisseriaceae

Neisserial lipooligosaccharide (LOS) contains three oligosaccharide chains, termed the alpha, beta, and gamma chains. We used Southern hybridization experiments on DNA isolated from various Neisseria spp. to determine if strains considered to be nonpathogenic possessed DNA sequences homologous with genes involved in the biosynthesis of these oligosaccharide chains. The presence or absence of specific genes was compared to the LOS profiles expressed by each strain, as characterized by their mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel and their reactivities with various LOS-specific monoclonal antibodies. A great deal of heterogeneity was seen with respect to the presence of genes encoding glycosyltransferases in Neisseria. All pathogenic species were found to possess DNA sequences homologous with the lgt gene cluster, a group of genes needed for the synthesis of the alpha chain. Some of these genes were also found to be present in strains considered to be nonpathogenic, such as Neisseria lactamica, N. subflava, and N. sicca. Some nonpathogenic Neisseria spp. were able to express high-molecular-mass LOS structures, even though they lacked the DNA sequences homologous with rfaF, a gene whose product must act before gonococcal and meningococcal LOS can be elongated. Using a PCR amplification strategy, in combination with DNA sequencing, we demonstrated that N. subflava 44 possessed lgtA, lgtB, and lgtE genes. The predicted amino acid sequence encoded by each of these genes suggested that they encoded functional proteins; however, structural analysis of LOS isolated from this strain indicated that the bulk of its LOS was not modified by these gene products. This suggests the existence of an additional regulatory mechanism that is responsible for the limited expression of these genes in this strain.     

Histo-blood group p: biosynthesis of globoseries glycolipids in EBV-transformed B cell lines

The genetic and biosynthetic basis of the histo-blood group P-system is not fully understood. Individuals with the rare p phenotype do not express the three glycolipid antigens (P^k, P and P₁) of this system, probably because of deficiencies in glycosyltransferases involved in their biosynthesis. Iiukaet al. [Iiuka S, Chen SH, Yoshida A (1986)Biochem Biophys Res Commun 137: 1187–95], however, previously reported that detergent extracts from an EBV-transformed B cell line derived from a p individual did express the glycosyltransferase activity (P^k transferase) assumed to be missing in this blood group status. Here, we have reinvestigated the antigen expression and glycosyltransferase activities in two p individuals by analysing EBV-transformed cell lines as well as erythrocytes to confirm the blood group P status. The thin layer chromatography glycolipid profile of extracts from erythrocytes and EBV-transformed B cell lines showed characteristic accumulation of lactosylceramide and absence of P^k and P antigens. Glycosyltransferase activities of the B cell lines were analysed using glycolipid substrates and both extracts were found to contain lactosylceramide synthetase and P transferase activities but to be completely devoid of P^k transferase activity. The presented data indicate that p individuals, in contrast to previous reports, do not express a functional P^k glycosyltransferase.Dedicated to Professor S. Hakomori in the occasion of his 65th birthday from two of his past posdoc's.     

Gene products required for surface expression of the capsular form of the group 1 K antigen in Escherichia coli (O9a:K30)

The group 1 K30 antigen from Escherichia coli (O9a:K30) is present on the cell surface as both a capsular structure composed of high-molecular-weight K30 polysaccharide and as short K30 oligosaccharides linked to lipid A-core in a lipopolysaccharide molecule (K30LPS). To determine the molecular processes that are responsible for the two forms of K antigen, the 16 kb chromosomal cps region has been characterized. This region encodes 12 gene products required for the synthesis, polymerization and translocation of the K30 antigen. The gene products include four glycosyltransferases responsible for synthesis of the K30 repeat unit; a PST (1) exporter (Wzx), required to transfer lipid-linked K30 units across the plasma membrane to the periplasmic space; and a K30-antigen polymerase (Wzy). These gene products are typical of those seen in O-antigen biosynthesis gene clusters and they interact with the lipopolysaccharide translocation pathway to express K30LPS on the cell surface. The same gene products also provide the biosynthetic intermediates for the capsule assembly pathway, although they are not in themselves sufficient for synthesis of the K30 capsule. Three additional genes, wza, wzb and wzc, encode homologues to proteins that are encoded by gene clusters involved in expression of a variety of bacterial exopolysaccharides. Mutant analysis indicates that Wza and Wzc are required for wild-type surface expression of the capsular structure but are not essential for polymerization and play no role in the translocation of K30LPS. These surface expression components provide the key feature that distinguishes the assembly systems for O antigens and capsules.     

Lewis antigens in Helicobacter pylori: biosynthesis and phase variation

The lipopolysaccharides (LPS) of most Helicobacter pylori strains contain complex carbohydrates known as Lewis antigens that are structurally related to the human blood group antigens. Investigations on the genetic determinants involved in the biosynthesis of Lewis antigens have led to the identification of the fucosyltransferases of H. pylori, which have substrate specificities distinct from the mammalian fucosyltransferases. Compared with its human host, H. pylori utilizes a different pathway to synthesize the difucosylated Lewis antigens, Lewis y. and Lewis b. Unique features in the H. pylori fucosyltransferase genes, including homopolymeric tracts mediating slipped-strand mispairing and the elements regulating translational frameshifting, enable H. pylori to produce variable LPS epitopes on its surface. These new findings have provided us with a basis to further examine the roles of molecular mimicry and phase variation of H. pylori Lewis antigen expression in both persistent infection and pathogenesis of this important human gastric pathogen.     

Novel UDP-GalNAc Derivative Structures Provide Insight into the Donor Specificity of Human Blood Group Glycosyltransferase

Two closely related glycosyltransferases are responsible for the final step of the biosynthesis of ABO(H) human blood group A and B antigens. The two enzymes differ by only four amino acid residues, which determine whether the enzymes transfer GalNAc from UDP-GalNAc or Gal from UDP-Gal to the H-antigen acceptor. The enzymes belong to the class of GT-A folded enzymes, grouped as GT6 in the CAZy database, and are characterized by a single domain with a metal dependent retaining reaction mechanism. However, the exact role of the four amino acid residues in the specificity of the enzymes is still unresolved. In this study, we report the first structural information of a dual specificity cis-AB blood group glycosyltransferase in complex with a synthetic UDP-GalNAc derivative. Interestingly, the GalNAc moiety adopts an unusual yet catalytically productive conformation in the binding pocket, which is different from the “tucked under” conformation previously observed for the UDP-Gal donor. In addition, we show that this UDP-GalNAc derivative in complex with the H-antigen acceptor provokes the same unusual binding pocket closure as seen for the corresponding UDP-Gal derivative. Despite this, the two derivatives show vastly different kinetic properties. Our results provide a important structural insight into the donor substrate specificity and utilization in blood group biosynthesis, which can very likely be exploited for the development of new glycosyltransferase inhibitors and probes.