Mixed-Up Sugars: Glycosyltransferase Cross-Reactivity in Cancerous Tissues and Their Therapeutic Targeting.
Chembiochem2 Nov 2021, . Epub 2 Nov 2021
The main categories of glycan changes in cancer are: (1) decreased expression of histo-blood group A and/or B antigens and increased Lewis-related antigens, (2) appearance of cryptic antigens, such as Tn and T, (3) emergence of genetically incompatible glycans, such as A antigen expressed in tumors of individuals of group B or O and heterophilic expression of Forssman antigen (FORS1), and (4) appearance of neoglycans. This review focuses on the expression of genetically incompatible A/B/FORS1 antigens in cancer. Several possible molecular mechanisms are exemplified, including missense mutations that alter the sugar specificity of A and B glycosyltransferases (AT and BT, respectively), restoration of the correct codon reading frame of O alleles, and modification of acceptor specificity of AT to synthesize the FORS1 antigen by missense mutations and/or altered splicing. Taking advantage of pre-existing natural immunity, the potential uses of these glycans for immunotherapeutic targeting will also be discussed.
Anderluh M, Berti F, Bzducha-Wróbel A, Chiodo F, Colombo C, Compostella F, Durlik K, Ferhati X, Holmdahl R, Jovanovic D, Kaca W, Lay L, Marinovic-Cincovic M, Marradi M, Ozil M, Polito L, Reina-Martin JJ, Reis CA, Sackstein R, Silipo A, Švajger U, Vaněk O, Yamamoto F, Richichi B, van Vliet SJ
Emerging glyco-based strategies to steer immune responses.
FEBS J16 Aug 2021, 288(16)4746-4772.
Glycan structures are common posttranslational modifications of proteins, which serve multiple important structural roles (for instance in protein folding), but also are crucial participants in cell-cell communications and in the regulation of immune responses. Through the interaction with glycan-binding receptors, glycans are able to affect the activation status of antigen-presenting cells, leading either to induction of pro-inflammatory responses or to suppression of immunity and instigation of immune tolerance. This unique feature of glycans has attracted the interest and spurred collaborations of glyco-chemists and glyco-immunologists to develop glycan-based tools as potential therapeutic approaches in the fight against diseases such as cancer and autoimmune conditions. In this review, we highlight emerging advances in this field, and in particular, we discuss on how glycan-modified conjugates or glycoengineered cells can be employed as targeting devices to direct tumor antigens to lectin receptors on antigen-presenting cells, like dendritic cells. In addition, we address how glycan-based nanoparticles can act as delivery platforms to enhance immune responses. Finally, we discuss some of the latest developments in glycan-based therapies, including chimeric antigen receptor (CAR)-T cells to achieve targeting of tumor-associated glycan-specific epitopes, as well as the use of glycan moieties to suppress ongoing immune responses, especially in the context of autoimmunity.
ABO blood group A transferases catalyze the biosynthesis of FORS blood group FORS1 antigen upon deletion of exon 3 or 4.
Blood Adv26 Dec 2017, 1(27)2756-2766. Epub 20 Dec 2017
Evolutionarily related ABO and GBGT1 genes encode, respectively, A and B glycosyltransferases (AT and BT) and Forssman glycolipid synthase (FS), which catalyze the biosynthesis of A and B, and Forssman (FORS1) oligosaccharide antigens responsible for the ABO and FORS blood group systems. Humans are a Forssman antigen-negative species; however, rare individuals with Apae phenotype express FORS1 on their red blood cells. We previously demonstrated that the replacement of the LeuGlyGly tripeptide sequence at codons 266 to 268 of human AT with GBGT1-encoded FS-specific GlyGlyAla enabled the enzyme to produce FORS1 antigen, although the FS activity was weak. We searched for additional molecular mechanisms that might allow human AT to express FORS1. A variety of derivative expression constructs of human AT were prepared. DNA was transfected into COS1 (B3GALNT1) cells, and cell-surface expression of FORS1 was immunologically monitored. To our surprise, the deletion of exon 3 or 4, but not of exon 2 or 5, of human AT transcripts bestowed moderate FS activity, indicating that the A allele is inherently capable of producing a protein with FS activity. Because RNA splicing is frequently altered in cancer, this mechanism may explain, at least partially, the appearance of FORS1 in human cancer. Furthermore, strong FS activity was attained, in addition to AT and BT activities, by cointroducing 1 of those deletions and the GlyGlyAla substitution, possibly by the synergistic effects of altered intra-Golgi localization/conformation by the former and modified enzyme specificity by the latter.
Evolutionary divergence of the ABO and GBGT1 genes specifying the ABO and FORS blood group systems through chromosomal rearrangements.
Sci Rep24 Aug 2017, 7(1)9375. Epub 24 Aug 2017
Human alleles at the ABO and GBGT1 genetic loci specify glycosylation polymorphism of ABO and FORS blood group systems, respectively, and their allelic basis has been elucidated. These genes are also present in other species, but presence/absence, as well as functionality/non-functionality are species-dependent. Molecular mechanisms and forces that created this species divergence were unknown. Utilizing genomic information available from GenBank and Ensembl databases, gene order maps were constructed of a chromosomal region surrounding the ABO and GBGT1 genes from a variety of vertebrate species. Both similarities and differences were observed in their chromosomal organization. Interestingly, the ABO and GBGT1 genes were found located at the boundaries of chromosomal fragments that seem to have been inverted/translocated during species evolution. Genetic alterations, such as deletions and duplications, are prevalent at the ends of rearranged chromosomal fragments, which may partially explain the species-dependent divergence of those clinically important glycosyltransferase genes.
Non-AUG start codons responsible for ABO weak blood group alleles on initiation mutant backgrounds.
Sci Rep31 Jan 2017, 741720. Epub 31 Jan 2017
Histo-blood group ABO gene polymorphism is crucial in transfusion medicine. We studied the activity and subcellular distribution of ABO gene-encoded A glycosyltransferases with N-terminal truncation. We hypothesized that truncated enzymes starting at internal methionines drove the synthesis of oligosaccharide A antigen in those already described alleles that lack a proper translation initiation codon. Not only we tested the functionality of the mutant transferases by expressing them and assessing their capacity to drive the appearance of A antigen on the cell surface, but we also analyzed their subcellullar localization, which has not been described before. The results highlight the importance of the transmembrane domain because proteins deprived of it are not able to localize properly and deliver substantial amounts of antigen on the cell surface. Truncated proteins with their first amino acid well within the luminal domain are not properly localized and lose their enzymatic activity. Most importantly, we demonstrated that other codons than AUG might be used to start the protein synthesis rather than internal methionines in translation-initiation mutants, explaining the molecular mechanism by which transferases lacking a classical start codon are able to synthesize A/B antigens.
Crosstalk between ABO and Forssman (FORS) blood group systems: FORS1 antigen synthesis by ABO gene-encoded glycosyltransferases.
Sci Rep30 Jan 2017, 741632. Epub 30 Jan 2017
A and B alleles at the ABO genetic locus specify A and B glycosyltransferases that catalyze the biosynthesis of A and B oligosaccharide antigens, respectively, of blood group ABO system which is important in transfusion and transplantation medicine. GBGT1 gene encodes Forssman glycolipid synthase (FS), another glycosyltransferase that produces Forssman antigen (FORS1). Humans are considered to be Forssman antigen-negative species without functional FS. However, rare individuals exhibiting Apae phenotype carry a dominant active GBGT1 gene and express Forssman antigen on RBCs. Accordingly, FORS system was recognized as the 31st blood group system. Mouse ABO gene encodes a cis-AB transferase capable of producing both A and B antigens. This murine enzyme contains the same GlyGlyAla tripeptide sequence as FSs at the position important for the determination of sugar specificity. We, therefore, transfected the expression construct into appropriate recipient cells and examined whether mouse cis-AB transferase may also exhibit FS activity. The result was positive, confirming the crosstalk between the ABO and FORS systems. Further experiments have revealed that the introduction of this tripeptide sequence to human A transferase conferred some, although weak, FS activity, suggesting that it is also involved in the recognition/binding of acceptor substrates, in addition to donor nucleotide-sugars.
Yamamoto F, Cid E, Yamamoto M, Saitou N, Bertranpetit J, Blancher A
An integrative evolution theory of histo-blood group ABO and related genes.
Sci Rep2014, 46601. Epub 13 Oct 2014
The ABO system is one of the most important blood group systems in transfusion/transplantation medicine. However, the evolutionary significance of the ABO gene and its polymorphism remained unknown. We took an integrative approach to gain insights into the significance of the evolutionary process of ABO genes, including those related not only phylogenetically but also functionally. We experimentally created a code table correlating amino acid sequence motifs of the ABO gene-encoded glycosyltransferases with GalNAc (A)/galactose (B) specificity, and assigned A/B specificity to individual ABO genes from various species thus going beyond the simple sequence comparison. Together with genome information and phylogenetic analyses, this assignment revealed early appearance of A and B gene sequences in evolution and potentially non-allelic presence of both gene sequences in some animal species. We argue: Evolution may have suppressed the establishment of two independent, functional A and B genes in most vertebrates and promoted A/B conversion through amino acid substitutions and/or recombination; A/B allelism should have existed in common ancestors of primates; and bacterial ABO genes evolved through horizontal and vertical gene transmission into 2 separate groups encoding glycosyltransferases with distinct sugar specificities.
Murine cell glycolipids customization by modular expression of glycosyltransferases.
PLoS ONE2013, 8(6)e64728. Epub 14 Jun 2013
Functional analysis of glycolipids has been hampered by their complex nature and combinatorial expression in cells and tissues. We report an efficient and easy method to generate cells with specific glycolipids. In our proof of principle experiments we have demonstrated the customized expression of two relevant glycosphingolipids on murine fibroblasts, stage-specific embryonic antigen 3 (SSEA-3), a marker for stem cells, and Forssman glycolipid, a xenoantigen. Sets of genes encoding glycosyltansferases were transduced by viral infection followed by multi-color cell sorting based on coupled expression of fluorescent proteins.
Transfus Med RevApr 2012, 26(2)103-18. Epub 23 Sep 2011
Research on ABO has advanced significantly in recent years. A database was established to manage the sequence information of an increasing number of novel alleles. Genome sequencings have identified ABO orthologues and paralogues in various organisms and enhanced the knowledge on the evolution of the ABO and related genes. The most prominent advancements include clarification of the association between ABO and different disease processes. For instance, ABO status affects the infectivity of certain strains of Helicobacter pylori and Noroviruses as well as the sequestration and rosetting of red blood cells infected with Plasmodium falciparum. Genome-wide association studies have conclusively linked the ABO locus to pancreatic cancer, venous thromboembolism, and myocardial infarction in the presence of coronary atherosclerosis. These findings suggest ABO's important role in determining an individual's susceptibility to such diseases. Furthermore, our understanding of the structures of A and B transferases and their enzymology has been dramatically improved. ABO has also become a research subject in neurobiology and the preparation of artificial/universal blood and became a topic in the pseudoscience of "blood type diets." With such new progress, it has become evident that ABO is a critical player in the modern era of genomic medicine. This article provides the most up-to-date information regarding ABO genomics.