Importance of molecular studies on major blood groups--intercellular adhesion molecule-4, a blood group antigen involved in multiple cellular interactions

Intercellular adhesion molecule 4 and ischemic stroke: a two-sample Mendelian randomization study

BACKGROUND

Experimental studies suggested that intercellular adhesion molecule 4 (ICAM-4) might be implicated in ischemic stroke, but the population-based evidence on the relationship between ICAM-4 and ischemic stroke were limited. Herein, we performed a two-sample Mendelian randomization (MR) analysis to investigate the associations of genetically determined plasma ICAM-4 with the risks of ischemic stroke and its subtypes.

METHODS

A total of 11 single-nucleotide polymorphisms associated with ICAM-4 were selected as instrumental variables based on the genome-wide association studies (GWAS) with 3,301 European individuals. Summary-level data about ischemic stroke and its subtypes were obtained from the Multi-ancestry GWAS launched by the International Stroke Genetics Consortium. We used the inverse-variance weighted method followed by a series of sensitivity analyses to evaluate the associations of genetically determined ICAM-4 with the risks of ischemic stroke and its subtypes.

RESULTS

Genetically determined higher ICAM-4 levels were significantly associated with increased risks of ischemic stroke (in the IVW method fitted to multiplicative random effects model: odds ratio [OR] per standard deviation [SD] increase, 1.04; 95% confidence interval [CI], 1.01-1.07; P = 0.006; in the IVW analysis with fixed effects model: OR per SD increase, 1.04; 95% CI, 1.01-1.07; P = 0.003) and cardioembolic stroke (in multiplicative random effects model: OR per SD increase, 1.08; 95% CI, 1.02-1.14; P = 0.004; in fixed effects model: OR per SD increase, 1.08; 95% CI, 1.03-1.13; P = 0.003). There was no association of ICAM-4 with the risks of large artery stroke and small vessel stroke. MR-Egger regression showed no directional pleiotropy for all associations, and the sensitivity analyses with different MR methods further confirmed these findings.

CONCLUSIONS

We found positive associations of genetically determined plasma ICAM-4 with the risks of ischemic stroke and cardioembolic stroke. Future studies are needed to explore the detailed mechanism and investigate the targeting effect of ICAM-4 on ischemic stroke.

Endothelial cell antibodies associated with novel targets and increased rejection

The initial contact point between a recipient's immune system and a transplanted graft is the vascular endothelium. Clinical studies suggest a pathogenic role for non-HLA antiendothelial cell antibodies (AECAs) in allograft rejection; however, evidence linking AECAs of known specificity to in vivo vascular injury is lacking. Here, we used high-density protein arrays to identify target antigens for AECAs isolated from the sera of recipients of kidney transplants experiencing antibody-mediated rejection in the absence of donor-specific HLA antibodies. Four antigenic targets expressed on endothelial cells were identified: endoglin, Fms-like tyrosine kinase-3 ligand, EGF-like repeats and discoidin I-like domains 3, and intercellular adhesion molecule 4; the first three have been implicated in endothelial cell activation and leukocyte extravasation. To validate these findings, ELISAs were constructed, and sera from an additional 150 renal recipients were tested. All four AECAs were detected in 24% of pretransplant sera, and they were associated with post-transplant donor-specific HLA antibodies, antibody-mediated rejection, and early transplant glomerulopathy. AECA stimulation of endothelial cell cultures increased adhesion molecule expression and production of inflammatory cytokines: regulated on activation, normal T cell expressed and secreted PDGF and RESISTIN. These correlations between in vitro experiments and in vivo histopathology suggest that AECAs activate the vascular endothelium, amplifying the alloimmune response and increasing microvascular damage. Given the growing number of transplant candidates, a better understanding of the antigenic targets, beyond HLA, and mechanisms of immune injury will be essential for improving long-term allograft survival.

Studies on the role of goat heart galectin-1 as a tool for detecting post-malignant changes in glycosylation pattern

Galectins are mammalian lectins established to play a crucial role in the progression of various cancer types by the virtue of their differential expression in normal and cancerous cells. In the present study, goat heart galectin-1 (GHG-1) was purified and investigated for its potential role in the detection of post-malignant changes in glycosylation pattern. When exposed to superoxide radicals generated from a pyrogallol auto-oxidation system, GHG-1 treated erythrocyte suspension released higher amount of oxyhemoglobin than the unagglutinated erythrocytes. The extent of erythrocyte hemolysis was found to be directly proportional to concentrations of hypochlorous acid. GHG-1 was used to detect the change in the β-galactoside expression pattern in erythrocyte membrane from human donors suffering from prostate and breast cancer. No significant change was observed in the hemolysis of lectin agglutinated erythrocytes collected from pre-operated breast cancer patients, whereas significant increase was observed in normal healthy control and post-operated samples. Findings of this study proclaim GHG-1 as an important tool for the detection of post-malignant changes in glycosylation pattern.

Genetic variation of the whole ICAM4 gene in Caucasians and African Americans

BACKGROUND

Landsteiner-Wiener (LW) is the human blood group system Number 16, which comprises two antithetical antigens, LW(a) and LW(b) and the high-prevalence antigen LW(ab) . LW is encoded by the intracellular adhesion molecule 4 (ICAM4) gene. The ICAM4 protein is part of the Rhesus complex in the red cell membrane and is involved in cell-cell adhesion.

STUDY DESIGN AND METHODS

We developed a method to sequence the whole 1.9-kb ICAM4 gene from genomic DNA in one amplicon. We determined the nucleotide sequence of Exons 1 to 3, the two introns, and 402-bp 5'-untranslated region (UTR) and 347-bp 3'-UTR in 97 Caucasian and 91 African American individuals.

RESULTS

Seven variant ICAM4 alleles were found, distinct from the wild-type ICAM4 allele (GenBank KF712272), known as LW*05 and encoding LW(a) . An effect of the LW(a) /LW(b) amino acid substitution on the protein structure was predicted by two of the three computational modeling programs used.

CONCLUSIONS

We describe a practical approach for sequencing and determining the ICAM4 alleles using genomic DNA. LW*05 is the ancestral allele, which had also been observed in a Neanderthal sample. All seven variant alleles are immediate derivatives of the prevalent LW*05 and caused by one single-nucleotide polymorphism (SNP) in each allele. Our data were consistent with the NHLBI GO Exome Sequencing Project (ESP) and the dbSNP databases, as all SNPs had been observed previously. Our study has the advantage over the other databases in that it adds haplotype (allele) information for the ICAM4 gene, clinically relevant in the field of transfusion medicine.

ICAM-5: a neuronal dendritic adhesion molecule involved in immune and neuronal functions

The neuron-specific intercellular adhesion molecule-5 (ICAM-5, telencephalin) is a member of the ICAM family of adhesion proteins. It has a complex structure with nine external immunoglobulin domains followed by a transmembrane and a cytoplasmic domain. The external part binds to beta1- and beta2-integrins and the matrix protein vitronectin, whereas its transmembrane domain binds to presenilins and the cytoplasmic domain to alpha-actinin and the ERM family of cytoplasmic proteins. In neurons it is confined to the soma and dendrites and it is enriched in dendritic filopodia with less expression in more mature dendritic spines. ICAM-5 strongly stimulates neurite outgrowth. ICAM-5 is cleaved by matrix metalloproteases upon activation of glutamate receptors or degraded through endocytosis resulting in increased spine maturation. Ablation of ICAM-5 expression increases functional synapse formation. The cleaved soluble fragment of ICAM-5 is immunosuppressive, which may be important in neuronal inflammatory diseases.

Longer storage of red blood cells is associated with increased in vitro erythrophagocytosis

BACKGROUND AND OBJECTIVES

Refrigerated storage of red blood cells (RBCs) induces numerous changes that may target the cells for erythrophagocytosis following transfusion. The influence of storage upon the phagocytosis of unseparated and fractionated young and old stored RBCs was investigated using two in vitro quantitative phagocytosis assays.

MATERIALS AND METHODS

Leucocyte-depleted RBC units were sampled at day 1 or 42 of storage. Young and old RBCs were fractionated at day 1 by density centrifugation and stored in paediatric packs for up to 42 days. RBCs were labelled with the fluorescent dye PKH26 and incubated with the human monocytic cell line THP-1. Erythrophagocytosis was quantified by flow cytometry and plate fluorometric assays.

RESULTS

A higher proportion of THP-1 cells phagocytosed RBCs stored for 42 days compared with 1 day (41% and 24% respectively; P<0·0001). This was associated with an increased mean number of RBCs phagocytosed per THP-1 cell (5·2±0·6 and 3·3±0·2 respectively; P<0·002). Erythrophagocytosis of fractionated young and old RBCs increased with longer storage duration up to 28 days (P<0·05). However, no significant differences were observed between erythrophagocytosis of young and old RBCs.

CONCLUSION

The susceptibility of stored RBCs to erythrophagocytosis significantly increased with longer storage time of the RBC units. Storage duration of RBCs had a greater influence on in vitro erythrophagocytosis than the chronological age of the RBCs at donation.

Intercellular adhesion molecule 1: recent findings and new concepts involved in mammalian spermatogenesis

Spermatogenesis, the process of spermatozoa production, is regulated by several endocrine factors, including testosterone, follicle stimulating hormone, luteinizing hormone and estradiol 17β. For spermatogenesis to reach completion, developing germ cells must traverse the seminiferous epithelium while remaining transiently attached to Sertoli cells. If germ cell adhesion were to be compromised for a period of time longer than usual, germ cells would slough from the seminiferous epithelium and infertility would result. Presently, Sertoli-germ cell adhesion is known to be mediated largely by classical and desmosomal cadherins. More recent studies, however, have begun to expand long-standing concepts and to examine the roles of other proteins such as intercellular adhesion molecules. In this review, we focus on the biology of intercellular adhesion molecules in the mammalian testis, hoping that this information is useful in the design of future studies.

Variation in the ICAM1-ICAM4-ICAM5 locus is associated with systemic lupus erythematosus susceptibility in multiple ancestries

OBJECTIVE

Systemic lupus erythematosus (SLE; OMIM 152700) is a chronic autoimmune disease for which the aetiology includes genetic and environmental factors. ITGAM, integrin α(M) (complement component 3 receptor 3 subunit) encoding a ligand for intracellular adhesion molecule (ICAM) proteins, is an established SLE susceptibility locus. This study aimed to evaluate the independent and joint effects of genetic variations in the genes that encode ITGAM and ICAM.

METHODS

The authors examined several markers in the ICAM1-ICAM4-ICAM5 locus on chromosome 19p13 and the single ITGAM polymorphism (rs1143679) using a large-scale case-control study of 17 481 unrelated participants from four ancestry populations. The single-marker association and gene-gene interaction were analysed for each ancestry, and a meta-analysis across the four ancestries was performed.

RESULTS

The A-allele of ICAM1-ICAM4-ICAM5 rs3093030, associated with elevated plasma levels of soluble ICAM1, and the A-allele of ITGAM rs1143679 showed the strongest association with increased SLE susceptibility in each of the ancestry populations and the trans-ancestry meta-analysis (OR(meta)=1.16, 95% CI 1.11 to 1.22; p=4.88×10(-10) and OR(meta)=1.67, 95% CI 1.55 to 1.79; p=3.32×10(-46), respectively). The effect of the ICAM single-nucleotide polymorphisms (SNPs) was independent of the effect of the ITGAM SNP rs1143679, and carriers of both ICAM rs3093030-AA and ITGAM rs1143679-AA had an OR of 4.08 compared with those with no risk allele in either SNP (95% CI 2.09 to 7.98; p=3.91×10(-5)).

CONCLUSION

These findings are the first to suggest that an ICAM-integrin-mediated pathway contributes to susceptibility to SLE.

Generation and characterisation of Rhd and Rhag null mice

Mouse Rhd* and Rhag* genes were targeted using insertional vectors; the resulting knockout mice, and double-knockout descendants, were analysed. Rhag glycoprotein deficiency entailed defective assembly of the erythroid Rh complex with complete loss of Rh and intercellular adhesion molecule 4 (ICAM-4), but not CD47, expression. Absence of the Rh protein induced a loss of ICAM-4, and only a moderate reduction of Rhag expression. Double knockout phenotype was similar to that of Rhag targeted mice. Rhd and Rhag deficient mice exhibited neither the equivalent of human Rh(null) haemolytic anaemia nor any clinical or cellular abnormalities. Rhd-/- and Rhag-/- erythrocytes showed decreased basal adhesion to an endothelial cell line resulting from defective ICAM-4 membrane expression. There was no difference in recovery from phenylhydrazine-induced haematopoietic stress for double knockout mice as compared to controls, suggesting that ICAM-4 might be dispensable during stress erythropoiesis. Ammonia and methylammonia transport in erythrocytes was severely impaired in Rhag-/- but only slightly in Rhd-/- animals that significantly expressed Rhag, supporting the view that RhAG and Rhag, but not Rh, may act as ammonium transporters in human and mouse erythrocytes. These knockout mice should prove useful for further dissecting the physiological roles of Rh and Rhag proteins in the red cell membrane.

Regulation of integrin activity and signalling

The ability of cells to attach to each other and to the extracellular matrix is of pivotal significance for the formation of functional organs and for the distribution of cells in the body. Several molecular families of proteins are involved in adhesion, and recent work has substantially improved our understanding of their structures and functions. Also, these molecules are now being targeted in the fight against disease. However, less is known about how their activity is regulated. It is apparent that among the different classes of adhesion molecules, the integrin family of adhesion receptors is unique in the sense that they constitute a large group of widely distributed receptors, they are unusually complex and most importantly their activities are strictly regulated from the inside of the cell. The activity regulation is achieved by a complex interplay of cytoskeletal proteins, protein kinases, phosphatases, small G proteins and adaptor proteins. Obviously, we are only in the beginning of our understanding of how the integrins function, but already now fascinating details have become apparent. Here, we describe recent progress in the field, concentrating mainly on mechanistical and structural studies of integrin regulation. Due to the large number of articles dealing with integrins, we focus on what we think are the most exciting and rewarding directions of contemporary research on cell adhesion and integrins.

ICAM-5--a novel two-facetted adhesion molecule in the mammalian brain

Cell adhesion is of utmost importance for normal development and cellular functions. ICAM-5 (intercellular adhesion molecule-5, telencephalin) is a member of the ICAM-family of adhesion proteins. These proteins bind to leukocyte beta(2)-integrins (CD11/CD18), but ICAM-5 is exceptional in several ways. It is solely expressed in the mammalian forebrain, appears at the time of birth, and is located in the soma and dendrites of neurons. It is structurally more complex than the others, and also shows homophilic adhesion. Recent studies show that it is important for the regulation of immunological activity in the brain and for the development of neuronal synapses and signal transmission.