The gene coding for the human T-lymphocyte CD2 antigen is located on chromosome 1p

Costimulatory Function of Cd58/Cd2 Interaction in Adaptive Humoral Immunity in a Zebrafish Model

CD58 and CD2 have long been known as a pair of reciprocal adhesion molecules involved in the immune modulations of CD8⁺ T and NK-mediated cellular immunity in humans and several other mammals. However, the functional roles of CD58 and CD2 in CD4⁺ T-mediated adaptive humoral immunity remain poorly defined. Moreover, the current functional observations of CD58 and CD2 were mainly acquired from in vitro assays, and in vivo investigation is greatly limited due to the absence of a Cd58 homology in murine models. In this study, we identified cd58 and cd2 homologs from the model species zebrafish (Danio rerio). These two molecules share conserved structural features to their mammalian counterparts. Functionally, cd58 and cd2 were significantly upregulated on antigen-presenting cells and Cd4⁺ T cells upon antigen stimulation. Blockade or knockdown of Cd58 and Cd2 dramatically impaired the activation of antigen-specific Cd4⁺ T and mIgM⁺ B cells, followed by the inhibition of antibody production and host defense against bacterial infections. These results indicate that CD58/CD2 interaction was required for the full activation of CD4⁺ T-mediated adaptive humoral immunity. The interaction of Cd58 with Cd2 was confirmed by co-immunoprecipitation and functional competitive assays by introducing a soluble Cd2 protein. This study highlights a new costimulatory mechanism underlying the regulatory network of adaptive immunity and makes zebrafish an attractive model organism for the investigation of CD58/CD2-mediated immunology and disorders. It also provides a cross-species understanding of the evolutionary history of costimulatory signals from fish to mammals as a whole.

Molecular analysis of CD2 gene expression in acute myeloblastic leukemia expressing T-lineage associated surface antigens

CD2 is a surface marker of T cells and NK cells, and is not normally expressed on human myeloid cells, but is found on a significant minority of cases of acute myeloid leukemia (AML). Molecular studies were performed on bone marrow myeloblasts from two patients with CD2 surface positive AML. No abnormality of the CD2 gene was detected on Southern blot analysis. On Northern blots, CD2 mRNA of normal size was present. The CD2 gene contained a site which was unmethylated, consistent with active transcription, in a CD2 positive AML case, and in a CD2 positive T cell line, but methylated in CD2 negative AML cells. The evidence does not support the hypothesis that inappropriate surface expression of lineage markers is due to leukemia-related genetic changes, such as amplification or rearrangement, of the CD2 gene itself. Rather, the results are consistent with the hypothesis that mixed lineage leukaemia arises from rare normal bone marrow progenitors with multilineage phenotypes.

Mutational analysis of the CD2/CD58 interaction: the binding site for CD58 lies on one face of the first domain of human CD2

The adhesion interaction between the immunoglobulin superfamily molecules CD2 and CD58 (lymphocyte function-associated antigen 3) plays an important role in T cell and natural killer cell interaction with various antigen-presenting and target cells. Determination of the solution structure of rat CD2 domain 1 has allowed a model of human CD2 domain 1 to be generated, and a series of mutants based on this model have been made. Residues of domain 1 of human CD2 predicted to be solvent exposed were substituted with the equivalent residues present in the rat CD2 molecule. The ability of these mutants to mediate rosetting with human and sheep erythrocytes was studied. Results show that the binding site of CD2 for both human and sheep CD58 maps to the beta sheet containing beta strands CC'C"F and G. Residues K34 and E36 in beta strand C, R48 and K49 in beta strand C', and K91 and N92 in the loop connecting beta strands F and G are shown to be critical in the interaction. The data support the proposition that the interaction between CD2 and CD58 involves the major beta sheet face of CD2.

Genomic organization and chromosomal localization of the human CTP synthetase gene (CTPS)

To elucidate the organization of the human genomic sequences encoding CTP synthetase (CTPS), fragments homologous to the cDNA were isolated from genomic lambda libraries. The fragments cloned were overlapping and cover over 40 kb. Cotransfection of the DNAs into CTPS-deficient, cytidine-requiring CHO mutants can transform them to cytidine-independent growth, indicating that the complete structural gene has been isolated. Direct sequencing and enzymatic amplification of the cloned genomic fragments revealed that the coding sequences are distributed to 19 exons covering about 35 kb. Multiple transcriptional start sites were detected by primer extension in a G + C-rich 5' flanking sequence that is separated from the translational start by an approximately 3-kb intron. A panel of human-rodent somatic cell hybrids and the CTPS cDNA were used to assign the structural gene to the short arm of human chromosome 1. This assignment was further refined through the use of somatic cell hybrids bearing fragments of the short arm of the chromosome, allowing localization to 1p36.11-p31, a region notable for its disruption in many types of tumors.

Gene structure, chromosomal location, and basis for alternative mRNA splicing of the human VCAM1 gene

Vascular cell adhesion molecule 1 (VCAM-1) is a cell surface glycoprotein adhesive for certain blood leukocytes and tumor cells, which is expressed by activated endothelium in a variety of pathologic conditions including atherosclerosis. Genomic clones encoding the VCAM1 gene were isolated and the organization of the gene was determined. The gene, which is present in a single copy in the human genome, contains 9 exons spanning approximately 25 kilobases of DNA. Exons 2-8 contain C2 or H-type immunoglobulin domains. At least two different VCAM-1 precursors can be generated from the human gene as a result of alternative mRNA splicing events, which include or exclude exon 5. A consensus TATAA element is located upstream of the transcriptional start site. The VCAM1 promoter contains consensus binding sites for NF-kappa B, the GATA family of transcription factors, as well as an AP1 site. The VCAM1 gene was assigned to the 1p31-32 region of chromosome 1 based on the analysis of human-mouse hybrid cell lines and in situ hybridization. Structural analysis of the human VCAM1 gene provides the basis for alternative mRNA splicing and an initial approach to elucidating the regulation of VCAM-1 expression.

1p13 is the most frequently involved band in structural chromosomal rearrangements in human breast cancer

Cytogenetic data on 14 breast carcinomas were examined to determine which chromosome arms and bands are preferentially involved in structural chromosome changes. Chromosome arms 17p, 16q, and 1p and band 1p13 were found to be significantly involved. A review of the world literature confirmed 1p as being the most frequently involved arm in structural chromosome changes in breast cancer and 1p13 as being the band most frequently involved in such changes. The two sets of results were pooled, and the analysis of 113 tumours revealed 229 of 304 bands to be involved, with 1p13 affected in 20% of the tumours.

Structure, expression, and genetic linkage of the mouse BCM1 (OX45 or Blast-1) antigen. Evidence for genetic duplication giving rise to the BCM1 region on mouse chromosome 1 and the CD2/LFA3 region on mouse chromosome 3

The mouse BCM1 (OX45, Blast-1) antigen has been cDNA cloned and sequenced to provide data supporting the view that BCM1, LFA3, and CD2 constitute a subgroup within the Ig superfamily. Mouse BCM1 is widely expressed on leukocytes and is likely to be anchored to the cell surface by a glycosyl-phosphatidylinositol anchor, as is the case for rat and human BCM1 antigen. Genetic linkage studies by recombination and pulse field analysis showed the BCM1 locus (Bcm-1) to be on distal mouse chromosome 1 and to be linked within 1,600 kb to the locus for an ATPase alpha chain gene (Atpa-3). A similar relationship was established between the human BCM1 locus (BCM1) and ATP1A2, and other markers on chromosome 1q. Conservation of genomic organization within a segment of human chromosome 1q and mouse chromosome 1 was demonstrated. A similar situation is seen in the region of the CD2 and LFA3 genes between mouse chromosome 3 and human chromosome 1p. Furthermore, the CD2/LFA3 genes are linked within 580 kb to Atpa-1/ATP1A1 genes to provide a parallel situation to the linkage between Bcm-1/BCM1 and Atpa-3/ATP1A2 on chromosomes 1 (mouse) and 1q (human). Taken together, the data suggest duplication of a chromosome region including the precursors of the genes for BCM1, CD2, and LFA3, and the ATPase genes to give rise to the linkage groups now observed. The duplicated regions may have stayed together on chromosome 1 in the human (with the insertion of a centromere), while in the mouse, the genetic regions are proposed to have become dispersed in the formation of chromosomes 1 and 3. CD2 and LFA3 are more dissimilar in sequence than BCM1 and LFA3, and if the precursors of the CD2 and LFA3 loci formed before the proposed chromosome segment duplication, then a gene encoding a recognizer molecule for BCM1 may exist in linkage with Bcm-1/BCM1 on chromosome 1 (mouse) and 1q (human).

Long-range restriction site mapping of a syntenic segment conserved between human chromosome 1 and mouse chromosome 3

A linkage map determined from segregation analysis of 338 meiotic events in an interspecific mouse cross was utilized to help investigate genomic organization of a linkage group conserved between human chromosome 1p and mouse chromosome 3. Using pulsed-field gel electrophoresis, the genes encoding the lymphocyte adhesion molecule human CD2/murine Ly-37, the alpha 1-subunit of Na, K-ATPase, the beta-subunit of thyrotropin, the beta-subunit of nerve growth factor, and muscle adenylate deaminase were similarly positioned on long-range restriction maps in both species. These studies indicate that the development of detailed genetic maps using interspecific Mus crosses facilitates rapid analysis of murine genomic organization and may enable physical mapping of syntenic regions within the human genome. Moreover, the data suggest profound conservation of genomic organization during mammalian evolution.

The structural biology of CD2

The CD2 molecule is a 50-55KD transmembrane glycoprotein expressed on the vast majority of thymocytes and virtually all peripheral T lymphocytes. Its functions are two-fold: adhesion and activation. CD2 serves to facilitate conjugate formation between the T-lineage cell and its cognate partner via intermolecular interaction of CD2 and LFA-3 on the former and latter cells, respectively. Perturbation of the CD2 extracellular segment by certain combinations of anti-CD2 MAbs or LFA-3 and a single anti-CD2 MAb activate T-lineage function. These CD2-mediated activation events also synergize with signals mediated through the TCR to augment T-cell response. Based on microchemical analysis of immunoaffinity-purified human CD2 and cDNA and genomic cloning of mouse and human molecules, considerable structural information is now available. The mature surface human CD2 molecule consists of 327 amino acids: a 185 aa extracellular segment; a 25 aa hydrophobic transmembrane segment; and a 117 aa cytoplasmic domain rich in prolines and basic residues. The CD2 gene is comprised of five exons which span approximately 12 Kb on chromosome 1. A similar protein structure and gene exon organization is found for the mouse CD2 homologue. The CD2 adhesion domain is approximately 103 aa in length and is encoded by a single exon (exon 2). This domain is resistant to proteolysis, even though it lacks any intrachain disulfides and, like the entire extracellular segment protein expressed in a baculovirus system, binds to its cellular ligand, LFA-3. The latter occurs with a micromolar Kd. This relatively low affinity suggests that multivalent interactions among CD2 monomers on the T cells and individual LFA-3 structures on the cognate partner are important in enhancing the avidity of the T-cell interaction with its target or stimulator cell. The affinity of the CD2 extracellular segment for LFA-3 is not affected by truncations in the CD2 cytoplasmic domain, implying that ligand binding is not regulated by intracellular mechanisms. Given that CD2 mRNA expression and surface CD2 copy number are increased by more than one order of magnitude post-TCR stimulation, it is more likely that adhesion via CD2 is modulated by alteration in surface copy number. Analysis of early transduction events occurring via CD3-Ti (TCR) and CD2 including single channel Ca2+ patch-clamp recordings on living human T lymphocytes indicate a virtual identity of signals.(ABSTRACT TRUNCATED AT 400 WORDS)

The human LFA-3 gene is located at the same chromosome band as the gene for its receptor CD2

Lymphocyte function-associated antigen 3 (LFA-3) is a widely distributed cell surface glycoprotein that has been assigned a role in cell-cell adhesion on the basis of its capacity to bind to the T-lymphocyte CD2 antigen. The amino acid sequences of the extracellular domains of these two antigens, predicted from their cDNA sequences, show significant similarities, and both are members of the immunoglobulin supergene family. In this communication, a probe prepared from LFA-3 cDNA has been used in Southern blot analyses of somatic cell hybrids and in in situ hybridization to assign the LFA-3 gene to the human chromosome band 1p13. This is the same location previously assigned to CD2. Thus the LFA-3 and CD2 genes have probably arisen by duplication of a common evolutionary precursor. These genes therefore represent a further instance in which related members of the immunoglobulin superfamily are located in adjacent regions of the genome.

Chromosomal localization of human Na+, K+-ATPase alpha- and beta-subunit genes

Na+, K+-ATPase is a heterodimeric enzyme responsible for the active maintenance of sodium and potassium gradients across the plasma membrane. Recently, cDNAs for several tissue-specific isoforms of the larger catalytic alpha-subunit and the smaller beta-subunit have been cloned. We have hybridized rat brain and human kidney cDNA probes, as well as human genomic isoform-specific DNA fragments, to Southern filters containing panels of rodent X human somatic cell hybrid lines. The results obtained have allowed us to assign the loci for the ubiquitously expressed alpha-chain (ATP1A1) to human chromosome 1, region 1p21----cen, and for the alpha 2 isoform that predominates in neural and muscle tissues (ATP1A2) to chromosome 1, region cen----q32. A common PstI RFLP was detected with the ATP1A2 probe. The alpha 3 gene, which is expressed primarily in neural tissues (ATP1A3), was assigned to human chromosome 19. A fourth alpha gene of unknown function (alpha D) that was isolated by molecular cloning (ATP1AL1) was mapped to chromosome 13. Although evidence to date had suggested a single gene for the beta-subunit, we found hybridizing restriction fragments derived from two different human chromosomes. On the basis of knowledge of conserved linkage groups on human and murine chromosomes, we propose that the coding gene ATP 1B is located on the long arm of human chromosome 1 and that the sequence on human chromosome 4 (ATP 1BL1) is either a related gene or a pseudogene.

Structure and function of the erythrocyte receptor CD2 on human T lymphocytes: a review

The human CD2 molecule is a 50kd surface glycoprotein expressed on greater than 95% of thymocytes and all peripheral T lymphocytes which mediates both adhesion between T cells and their targets, and subsequent T cell activation events. Molecular cloning of human CD2 cDNAs predicts a mature CD2 protein of 327 amino acids, with an extracellular segment of 185 amino acids, a transmembrane domain of 24 amino acids and an intracytoplasmic region of 117 amino acids. Genomic cloning shows that the extracellular segment is encoded by two exons, the transmembrane segment by a single exon and the intracytoplasmic region by a single exon. Expression and biochemical analysis of a soluble extracellular domain CD2 molecule reveal that it expresses native CD2 epitopes and contains a stable 15kd NH2-terminal fragment corresponding to a single exon. Binding analyses of the soluble CD2 molecule indicate that it binds specifically to a known cell-surface ligand for CD2 at a relatively low affinity, thus suggesting that T cell-target adhesion mediated by CD2 and its ligand depends on multimeric attachment between an array of CD2 molecules and their cognate ligands.