CEACAM1 Isoforms Research Articles

CEACAM expression in an in-vitro prostatitis model.

Prostatitis is an inflammatory disease of the prostate gland, which affects 2-16% of men worldwide and thought to be a cause for prostate cancer (PCa) development. Carcinoembryogenic antigen-related cell adhesion molecules (CEACAMs) are deregulated in inflammation and in PCa. The role of CEACAMs in prostate inflammation and their possible contribution to the malignant transformation of prostate epithelial cells is still elusive. In this study, we investigated the expression of CEACAMs in an in-vitro prostatitis model and their potential role in malignant transformation of prostate epithelial cells. Normal prostate epithelial RWPE-1 cells were treated with pro-inflammatory cytokines to achieve an inflammatory state of the cells. The expression of CEACAMs and their related isoforms were analyzed. Additionally, the expression levels of selected CEACAMs were correlated with the expression of malignancy markers and the migratory properties of the cells. This study demonstrates that the pro-inflammatory cytokines, tumor necrosis factor alpha (TNFα) and interferon-gamma (IFNγ), induce synergistically an up-regulation of CEACAM1 expression in RWPE-1 cells, specifically favoring the CEACAM1-L isoform. Furthermore, overexpressed CEACAM1-L is associated with the deregulated expression of JAK/STAT, NFκB, and epithelial-mesenchymal transition (EMT) genes, as well as an increased cell migration. We postulate that CEACAM1 isoform CEACAM1-4L may synergistically contribute to inflammation-induced oncogenesis in the prostate.

Unaltered Fungal Burden and Lethality in Human CEACAM1-Transgenic Mice During Candida albicans Dissemination and Systemic Infection.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, CD66a) is a receptor for Candida albicans. It is crucial for the immune response of intestinal epithelial cells to this opportunistic pathogen. Moreover, CEACAM1 is of importance for the mucosal colonization by different bacterial pathogens. We therefore studied the influence of the human CEACAM1 receptor in human CEACAM1-transgenic mice on the C. albicans colonization and infection utilizing a colonization/dissemination and a systemic infection mouse model. Our results showed no alterations in the host response between the transgenic mice and the wild-type littermates to the C. albicans infections. Both mouse strains showed comparable C. albicans colonization and mycobiota, similar fungal burdens in various organs, and a similar survival in the systemic infection model. Interestingly, some of the mice treated with anti-bacterial antibiotics (to prepare them for C. albicans colonization via oral infection) also showed a strong reduction in endogenous fungi instead of the normally observed increase in fungal numbers. This was independent of the expression of human CEACAM1. In the systemic infection model, the human CEACAM1 expression was differentially regulated in the kidneys and livers of Candida-infected transgenic mice. Notably, in the kidneys, a total loss of the largest human CEACAM1 isoform was observed. However, the overwhelming immune response induced in the systemic infection model likely covered any CEACAM1-specific effects in the transgenic animals. In vitro studies using bone marrow-derived neutrophils from both mouse strains also revealed no differences in their reaction to C. albicans. In conclusion, in contrast to bacterial pathogens interacting with CEACAM1 on different mucosal surfaces, the human CEACAM1-transgenic mice did not reveal a role of human CEACAM1 in the in vivo candidiasis models used here. Further studies and different approaches will be needed to reveal a putative role of CEACAM1 in the host response to C. albicans.

Studying Variations in CEACAM1 Nanoscale Organization, Structure, and Dynamics

CEACAMs are cell surface glycoproteins involved in homo- and hetero-philic intercellular interactions that control cellular growth, differentiation, tumourigenesis, inflammation and infection. There is growing evidence regarding the role that CEACAM1 isoforms play in regulating interactions between various cell types. In particular, given its potential as a tumour suppressor or immunomodulator, CEACAM1 is being targeted in clinical trials. However, there remain clear challenges owing to observation that different CEACAM1 isoforms display cell-type specific preferential expression patterns under different physiological conditions. Moreover, the ability of CEACAMs to form dimers and higher-order oligomers, which are thought to impact regulation of intercellular signals, adds considerable complexity to our understanding of its functional role(s). Super resolution microscopy has enabled the quantitative characterization of the nanoscale distribution of many membrane proteins, including their ability to form both micro- and nano-scale clusters. However, clustering and self-association are not necessarily the same and mapping how oligomeric state impact clustering and / or the oligomeric state of the proteins within a cluster is of particular interest to many. We report here on the development and application of a correlative STORM/homoFRET strategy to study CEACAM1 isoforms and mutants. This approach exploits eYFP for homoFRET measurements, an Alexa Fluor 647 (AF647) labeled an anti-eYFP single domain antibody (nanobody) for dSTORM, and Voronoi tessalation to perform cluster analysis of dSTORM dataset. Building on these data, we have also applied co-localization approaches to measure the CEACAM1 association to lipid-ordered regions, ezrin, and actin. We have further explored the use of single particle tracking (SPT) and mean square displacement analysis (MSD) to characterize CEACAM1 dynamics as a function of oligomeric state and location. These studies have helped develop a more fulsome perspective on the structure, association, and dynamics of this important class of membrane proteins.

Carcinoembryonic antigen (CEA)-related cell adhesion molecules are co-expressed in the human lung and their expression can be modulated in bronchial epithelial cells by non-typable Haemophilus influenzae, Moraxella catarrhalis, TLR3, and type I and II interferons

The carcinoembryonic antigen (CEA)-related cell adhesion molecules CEACAM1 (BGP, CD66a), CEACAM5 (CEA, CD66e) and CEACAM6 (NCA, CD66c) are expressed in human lung. They play a role in innate and adaptive immunity and are targets for various bacterial and viral adhesins. Two pathogens that colonize the normally sterile lower respiratory tract in patients with chronic obstructive pulmonary disease (COPD) are non-typable Haemophilus influenzae (NTHI) and Moraxella catarrhalis. Both pathogens bind to CEACAMs and elicit a variety of cellular reactions, including bacterial internalization, cell adhesion and apoptosis. To analyze the (co-) expression of CEACAM1, CEACAM5 and CEACAM6 in different lung tissues with respect to COPD, smoking status and granulocyte infiltration, immunohistochemically stained paraffin sections of 19 donors were studied. To address short-term effects of cigarette smoke and acute inflammation, transcriptional regulation of CEACAM5, CEACAM6 and different CEACAM1 isoforms by cigarette smoke extract, interferons, Toll-like receptor agonists, and bacteria was tested in normal human bronchial epithelial (NHBE) cells by quantitative PCR. Corresponding CEACAM protein levels were determined by flow cytometry. Immunohistochemical analysis of lung sections showed the most frequent and intense staining for CEACAM1, CEACAM5 and CEACAM6 in bronchial and alveolar epithelium, but revealed no significant differences in connection with COPD, smoking status and granulocyte infiltration. In NHBE cells, mRNA expression of CEACAM1 isoforms CEACAM1-4L, CEACAM1-4S, CEACAM1-3L and CEACAM1-3S were up-regulated by interferons alpha, beta and gamma, as well as the TLR3 agonist polyinosinic:polycytidylic acid (poly I:C). Interferon-gamma also increased CEACAM5 expression. These results were confirmed on protein level by FACS analysis. Importantly, also NTHI and M. catarrhalis increased CEACAM1 mRNA levels. This effect was independent of the ability to bind to CEACAM1. The expression of CEACAM6 was not affected by any treatment or bacterial infection. While we did not find a direct correlation between CEACAM1 expression and COPD, the COPD-associated bacteria NTHi and M. catarrhalis were able to increase the expression of their own receptor on host cells. Further, the data suggest a role for CEACAM1 and CEACAM5 in the phenomenon of increased host susceptibility to bacterial infection upon viral challenge in the human respiratory tract.

CEACAM1 deficiency exacerbates acute liver injury in a mouse model of immune-mediated hepatitis

Introduction: Injection of a sublethal dose of the T cell mitogenic plant lectin concanavalin A (ConA) induces acute immune-mediated liver injury. Hallmarks of liver injury are increased plasma transaminase activities and the release of pro-inflammatory cytokines. CEACAM1 is a cellular adhesion molecule that is expressed on epithelia, endothelia, and leukocytes. Originally, CEACAM1 has been identified as an intercellular homophilic adhesion molecule on hepatocytes. The CEACAM1 isoform with a long cytoplasmic domain contains an immune receptor tyrosine-based inhibition motif (ITIM) that is pivotal in for its negative regulation of leukocyte activation.

Carcinoembryonic antigen (CEA)-related cell adhesion molecules are co-expressed in the human lung and their expression can be modulated in bronchial epithelial cells by non-typable Haemophilus influenzae, Moraxella catarrhalis, TLR3, and type I and II interferons

BackgroundThe carcinoembryonic antigen (CEA)-related cell adhesion molecules CEACAM1 (BGP, CD66a), CEACAM5 (CEA, CD66e) and CEACAM6 (NCA, CD66c) are expressed in human lung. They play a role in innate and adaptive immunity and are targets for various bacterial and viral adhesins. Two pathogens that colonize the normally sterile lower respiratory tract in patients with chronic obstructive pulmonary disease (COPD) are non-typable Haemophilus influenzae (NTHI) and Moraxella catarrhalis. Both pathogens bind to CEACAMs and elicit a variety of cellular reactions, including bacterial internalization, cell adhesion and apoptosis.MethodsTo analyze the (co-) expression of CEACAM1, CEACAM5 and CEACAM6 in different lung tissues with respect to COPD, smoking status and granulocyte infiltration, immunohistochemically stained paraffin sections of 19 donors were studied. To address short-term effects of cigarette smoke and acute inflammation, transcriptional regulation of CEACAM5, CEACAM6 and different CEACAM1 isoforms by cigarette smoke extract, interferons, Toll-like receptor agonists, and bacteria was tested in normal human bronchial epithelial (NHBE) cells by quantitative PCR. Corresponding CEACAM protein levels were determined by flow cytometry.ResultsImmunohistochemical analysis of lung sections showed the most frequent and intense staining for CEACAM1, CEACAM5 and CEACAM6 in bronchial and alveolar epithelium, but revealed no significant differences in connection with COPD, smoking status and granulocyte infiltration. In NHBE cells, mRNA expression of CEACAM1 isoforms CEACAM1-4L, CEACAM1-4S, CEACAM1-3L and CEACAM1-3S were up-regulated by interferons alpha, beta and gamma, as well as the TLR3 agonist polyinosinic:polycytidylic acid (poly I:C). Interferon-gamma also increased CEACAM5 expression. These results were confirmed on protein level by FACS analysis. Importantly, also NTHI and M. catarrhalis increased CEACAM1 mRNA levels. This effect was independent of the ability to bind to CEACAM1. The expression of CEACAM6 was not affected by any treatment or bacterial infection.ConclusionsWhile we did not find a direct correlation between CEACAM1 expression and COPD, the COPD-associated bacteria NTHi and M. catarrhalis were able to increase the expression of their own receptor on host cells. Further, the data suggest a role for CEACAM1 and CEACAM5 in the phenomenon of increased host susceptibility to bacterial infection upon viral challenge in the human respiratory tract.

Clinical and experimental studies regarding the expression and diagnostic value of carcinoembryonic antigen-related cell adhesion molecule 1 in non-small-cell lung cancer

BackgroundCarcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a multifunctional Ig-like cell adhesion molecule that has a wide range of biological functions. According to previous reports, serum CEACAM1 is dysregulated in different malignant tumours and associated with tumour progression. However, the serum CEACAM1 expression in non-small-cell lung carcinomas (NSCLC) is unclear. The different expression ratio of CEACAM1-S and CEACAM1-L isoform has seldom been investigated in NSCLC. This research is intended to study the serum CEACAM1 and the ratio of CEACAM1-S/L isoforms in NSCLC.MethodsThe expression of the serum CEACAM1 was determined by enzyme-linked immunosorbent assay. The protein expression and the location of CEACAM1 in tumours were observed by immunohistochemical staining. The CEACAM1 mRNA levels in tumour and normal adjacent tissues were measured using quantitative real-time PCR, and the expression patterns and the rate of CEACAM1-S and CEACAM1-L were analysed by reverse transcription-PCR.ResultsSerum CEACAM1 levels were significantly higher in NSCLC patients compared with that from normal healthy controls (P <0.0001). 17 patients (81%) among 21 showed high expression of CEACAM1 by immunohistochemical staining. Although no significant differences were found between tumour and normal tissues on mRNA expression levels of CEACAM1 (P >0.05), the CEACAM1-S and the CEACAM1-S/L (S: L) ratios were significantly higher in tumour than normal tissues (P <0.05).ConclusionsOur data indicated that the serum levels of CEACAM1 could discriminate lung cancer patients from health donors and that CEACAM1 might be a useful marker in early diagnosis of NSCLC. Moreover, our results showed that the expression patterns of CEACAM1 isoforms could be changed during oncogenesis, even when total CEACAM1 in tumour tissues did not show significant changes. Our study suggested that the expression ratios of CEACAM1-S/CEACAM1-L might be a better diagnostic indicator in NSCLC than the quantitative changes of CEACAM1.

54 CEACAM1 in Brain Development and Preterm Brain Injury

Background and aimsAbout 10% of all neonates are born preterm before 37 weeks of gestation. These babies are at high risk to develop morbidities such as neurocognitive disorders (encephalopathy of...

Homophilic adhesion and CEACAM1-S regulate dimerization of CEACAM1-L and recruitment of SHP-2 and c-Src

Carcinoembryonic antigen (CEA)-related cell adhesion molecule 1 (CAM1 [CEACAM1]) mediates homophilic cell adhesion and regulates signaling. Although there is evidence that CEACAM1 binds and activates SHP-1, SHP-2, and c-Src, knowledge about the mechanism of transmembrane signaling is lacking. To analyze the regulation of SHP-1/SHP-2/c-Src binding, we expressed various CFP/YFP-tagged CEACAM1 isoforms in epithelial cells. The supramolecular organization of CEACAM1 was examined by cross-linking, coclustering, coimmunoprecipitation, and fluorescence resonance energy transfer. SHP-1/SHP-2/c-Src binding was monitored by coimmunoprecipitation and phosphotyrosine-induced recruitment to CEACAM1-L in cellular monolayers. We find that trans-homophilic CEACAM1 binding induces cis-dimerization by an allosteric mechanism transmitted by the N-terminal immunoglobulin-like domain. The balance of SHP-2 and c-Src binding is dependent on the monomer/dimer equilibrium of CEACAM1-L and is regulated by trans-binding, whereas SHP-1 does not bind under physiological conditions. CEACAM1-L homodimer formation is reduced by coexpression of CEACAM1-S and modulated by antibody ligation. These data suggest that transmembrane signaling by CEACAM1 operates by alteration of the monomer/dimer equilibrium, which leads to changes in the SHP-2/c-Src-binding ratio.

Editorial: CEACAM1: fine-tuned for fine-tuning

Editorial: CEACAM1: fine-tuned for fine-tuning

Genetic construction, expression, and characterization of a single chain anti-CEA antibody fused to cytosine deaminase from yeast

We report the genetic construction and expression of a fusion protein between a single chain fragment variable (scFv) human antibody (E8) specific for CEA cell surface antigen and yeast cytosine deaminase (yCD). Sequences encoding for the scFvE8 human monoclonal antibody recognizing an epitope shared by CEACAM1, CEACAM3 and CEACAM5 isoforms were assembled with a monomer of yCD. The construct was placed under the transcriptional regulation of the lac promoter, and in frame with 6xHis tag for protein purification. After transformation and induction of E. coli, the protein was recovered from cell lysates and processed for purification. The scFvE8:yCD fusion protein possessed the binding specificity for melanoma (Mel P5) and colon carcinoma (LoVo) cell lines similar to its cognate human scFv antibody. The scFv8:yCD system showed the ability to render tumor cells susceptible to the far less toxic substrate 5-fluorocytosine (5-FC) by its enzymatic conversion into 5-fluorouracil (5-FU). In vitro pre-treatment of Mel P5 and LoVo cell lines with scFvE8:yCD followed by cell washing and incubation with 5-FC, resulted in significant cell killing supporting the utility of this fusion protein as an agent for tumor-selective prodrug activation. This study shows the feasibility of constructing fusion proteins in a prokaryotic cell based system consisting of a human scFv antibody and yCD to convert the antifungal agent 5-FC to 5-FU, one of the widely used anticancer agent.

The Cell Adhesion Receptor Carcinoembryonic Antigen-related Cell Adhesion Molecule 1 Regulates Nucleocytoplasmic Trafficking of DNA Polymerase δ-Interacting Protein 38

The homophilic cell-cell adhesion receptor CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1, CD66a) acts as a regulator of contact-dependent cell survival, differentiation, and growth. It is involved in the control of proliferation in hematopoietic and epithelial cells and can act as a tumor suppressor. In this study, we identify DNA polymerase delta-interacting protein 38 (PDIP38) as a novel binding partner for CEACAM1-L and CEACAM1-S. We show that PDIP38 can occur in the nucleus, in the cytoplasm and at the plasma membrane in NBT-II, IEC18, RBE, and HeLa cells and that the distribution in NBT-II cells is influenced by the confluency of the cells. We also demonstrate that the interaction of CEACAM1 and PDIP38 is of functional importance in NBT-II cells, which co-express the long and the short CEACAM1 isoform. In subconfluent, proliferating NBT-II cells, perturbation of CEACAM1 by antibody clustering induces increased binding to PDIP38 and results in rapid recruitment of PDIP38 to the plasma membrane. The same treatment of confluent, quiescent NBT-II cells leads to a different response, i.e. translocation of PDIP38 to the nucleus. Together, our data show that PDIP38 can shuttle between the cytoplasmic and the nuclear compartments and that its subcellular localization is regulated by CEACAM1, implicating that PDIP38 may constitute a novel downstream target of CEACAM1 signaling.

Transmembrane CEACAM1 affects integrin-dependent signaling and regulates extracellular matrix protein–specific morphology and migration of endothelial cells

AbstractCarcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1/CD66a), expressed on leukocytes, epithelia, and endothelia mediates homophilic cell adhesion. It plays an important role in cell morphogenesis and, recently, soluble CEACAM1 isoforms have been implicated in angiogenesis. In the present study, we investigated the function of long transmembrane isoform of CEACAM1 (CEACAM1-L) in cultured rat brain endothelial cells. We observed that expression of CEACAM1-L promotes network formation on basement membrane Matrigel and increased cell motility after monolayer injury. During cell-matrix adhesion, CEACAM1-L translocated into the Triton X-100–insoluble cytoskeletal fraction and affected cell spreading and cell morphology on Matrigel and laminin-1 but not on fibronectin. On laminin-1, CEACAM1-L–expressing cells developed protrusions with lamellipodia, showed less stress fiber formation, reduced focal adhesion kinase (FAK) tyrosine phosphorylation, and decreased focal adhesion formation leading to high motility. CEACAM1-L–mediated morphologic alterations were sensitive to RhoA activation via lysophosphatidic acid (LPA) treatment and dependent on Rac1 activation. Furthermore, we demonstrate a matrix protein–dependent association of CEACAM1-L with talin, an important regulator of integrin function. Taken together, our results suggest that transmembrane CEACAM1-L expressed on endothelial cells is implicated in the activation phase of angiogenesis by affecting the cytoskeleton architecture and integrin-mediated signaling.

Identification of allelic variants of the bovine immune regulatory molecule CEACAM1 implies a pathogen-driven evolution

Carcinoembryonic antigen-related cell adhesion molecule (CEACAM1), the primordial member of the carcinoembryonic antigen (CEA) family, functions as a MHC-independent natural killer (NK) cell inhibitory receptor, regulates T and B cell proliferation, and induces dendritic cell (DC) maturation. Despite these fundamental functions, CEACAM1 and most of the CEA family members differ significantly in primates and rodents. A number of diverse murine and human pathogens use CEACAM1 as a cellular receptor, indicating that the observed species-specific differences are the result of divergent molecular pathogen/host coevolution. To gain deeper insight into its evolution and function, we cloned CEACAM1 cDNA from cattle as a representative of a third mammalian order. Bovine CEACAM1 differs considerably from rodent and primate CEACAM1 due to deletion of the B domain exon which was most likely caused by insertion of LINE/SINE sequences and reveals alternative splicing within the transmembrane exon. However, the characteristic long and short isoforms exist which contain or lack the typical immunoreceptor tyrosine-based inhibitory motifs (ITIM) in their cytoplasmic tails, respectively. Bovine peripheral blood lymphocytes (PBL) express only ITIM-containing CEACAM1 isoforms, and upregulate their expression upon stimulation, suggesting an inhibitory function in these cells. As found in rodents, two clearly distinct CEACAM1 alleles exist in cattle. In the a allele, a unique deletion of three amino acids is found in the N domain, which is important for pathogen binding in mice and humans. This is consistent with the notion that CEACAM1 serves or has served as a pathogen receptor in cattle.

Carcinoembryonic antigen-related cellular adhesion molecule 1 isoforms alternatively inhibit and costimulate human T cell function.

Carcinoembryonic Ag-related cellular adhesion molecule 1 (CEACAM1) represents a group of transmembrane protein isoforms that consist of variable numbers of extracellular Ig-like domains together with either a long cytoplasmic (cyt) tail containing two immunoreceptor tyrosine-based inhibitory motifs or a unique short cyt tail. Although CEACAM1 has been reported to be expressed on the surface of T lymphocytes upon activation, its roles in T cell regulation are controversial due to the lack of functional characterization of each individual CEACAM1 isoform. We thus cotransfected Jurkat T cells with CEACAM1 isoform-encoding constructs and an IL-2 promoter-bearing plasmid or a small interference RNA targeting src homology domain 2 containing phosphatase 1. In a luciferase reporter assay and through measurements of cytokine secretion (IL-2, IL-4, and IFN-gamma), CEACAM1 containing either a long or a short cyt tail inhibited or costimulated, respectively, TCR/CD3 complex plus CD28 mediated activation with the inhibitory functions of the long cyt tail dominating. The inhibitory function of CEACAM1, was dependent upon src homology domain 2 containing phosphatase 1 activity, required both tyrosine residues within the immunoreceptor tyrosine-based inhibitory motif domains of the cyt tail and was mediated through the mitogen-activated protein kinase pathway. CEACAM1-mediated inhibition could be functionally reconstituted by incubation of PBMC with either a CEACAM1-specific mAb or CEACAM1-Fc fusion protein in the presence of an allogeneic or mitogenic stimulus, respectively. These studies indicate that the long and short cyt tails of CEACAM1 serve as inhibitory and costimulatory receptors, respectively, in T cell regulation.

The cytoplasmic domain of CEACAM1-L controls its lateral localization and the organization of desmosomes in polarized epithelial cells.

Two CEACAM1 isoforms with different cytoplasmic domains, CEACAM1-L and CEACAM1-S, are unequally distributed in polarized epithelial MDCK cells. CEACAM1-S is exclusively apical whereas CEACAM1-L occurs both in apical and lateral cell surfaces. Using confocal microscopy and CEACAM1-L mutants, we identified several amino acids in the cytoplasmic domain that were instrumental for the lateral localization. Tyr515, but not Tyr488, constituted a prominent lateral targeting signal. Pervanadate-stimulated Tyr phosphorylation induced rapid phosphatidylinositol 3-kinase-dependent disappearance of lateral CEACAM1-L, whereas staurosporine, a Ser/Thr kinase inhibitor, resulted in slower phosphatidylinositol 3-kinase-independent disappearance. Both drugs caused accumulation of CEACAM1-L in a late endosome/lysosome compartment. Colocalization studies of occludin, ZO-1, E-cadherin, beta-catenin and desmoplakin indicated that laterally localized CEACAM1-L was present in adherens junctions but not in tight junctions or desmosomes. Overexpressed CEACAM1-L did not affect the organization of tight junction or adherens junction proteins, but perturbed the arrangement of desmosomes. The abundance of desmosomes in the lateral cell surfaces decreased significantly and the submembraneous cytokeratin filaments became disorganized. The signal for desmosomal perturbance resided within amino acids 484-518 in the C-terminal part of the cytoplasmic domain, among which an intact Tyr515 was indispensable.

CEACAM1 is a potent regulator of B cell receptor complex-induced activation.

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, CD66a) is a member of the immunoglobulin (Ig) superfamily, previously characterized as an adhesion and signaling molecule in epithelial, endothelial, and hematopoietic cells. Here, we show that the CEACAM1 isoform expression pattern is different in nonactivated and activated primary mouse B lymphocytes and that CEACAM1 influences B cell receptor complex-mediated activation. A CEACAM1-specific monoclonal antibody strongly triggered proliferation of mouse B cells when combined with surface IgM cross-linking. However, anti-CEACAM1 was not mitogenic when added alone. The proliferation was more pronounced and lasted longer as compared with other activators of B cells, such as anti-IgM in the presence of interleukin-4 or lipopolysaccharide. A similar, costimulatory effect was exerted by CEACAM1-expressing fibroblasts, indicating that homophilic CEACAM1-CEACAM1 cell-mediated binding is the physiological stimulus for CEACAM1-triggered B cell signaling. The anti-CEACAM1/anti-IgM-activated cells aggregated in a lymphocyte function-associated antigen-1-dependent manner. Furthermore, cells that were activated by anti-CEACAM1/anti-IgM secreted Ig but did not go through Ig class-switching. Anti-CEACAM1 induced phosphorylation of c-Jun N-terminal kinase (stress-activated protein kinase) but did not activate the extracellular signal-regulated kinase or p38 mitogen-activated protein kinases.

SHP-1 dependent and independent suppression of colitis by a CEACAM1 isoform expressing a long cytoplasmic tail

SHP-1 dependent and independent suppression of colitis by a CEACAM1 isoform expressing a long cytoplasmic tail

Targeted disruption of the Ceacam1 (MHVR) gene leads to reduced susceptibility of mice to mouse hepatitis virus infection.

The CEACAM1 glycoproteins (formerly called biliary glycoproteins; BGP, C-CAM, CD66a, or MHVR) are members of the carcinoembryonic antigen family of cell adhesion molecules. In the mouse, splice variants of CEACAM1 have either two or four immunoglobulin (Ig) domains linked through a transmembrane domain to either a short or a long cytoplasmic tail. CEACAM1 has cell adhesion activity and acts as a signaling molecule, and long-tail isoforms inhibit the growth of colon and prostate tumor cells in rodents. CEACAM1 isoforms serve as receptors for several viral and bacterial pathogens, including the murine coronavirus mouse hepatitis virus (MHV) and Haemophilus influenzae, Neisseria gonorrhoeae, and Neisseria meningitidis in humans. To elucidate the mechanisms responsible for the many biological activities of CEACAM1, we modified the expression of the mouse Ceacam1 gene in vivo. Manipulation of the Ceacam1 gene in mouse embryonic stem cells that contained the Ceacam1a allele yielded a partial knockout. We obtained one line of mice in which the insert in the Ceacam1a gene had sustained a recombination event. This resulted in the markedly reduced expression of the two CEACAM1a isoforms with four Ig domains, whereas the expression of the two isoforms with two Ig domains was doubled relative to that in wild-type BALB/c (+/+) mice. Homozygous (p/p) Ceacam1a-targeted mice (Ceacam1aDelta4D) had no gross tissue abnormalities and were viable and fertile; however, they were more resistant to MHV A59 infection and death than normal (+/+) mice. Following intranasal inoculation with MHV A59, p/p mice developed markedly fewer and smaller lesions in the liver than +/+ or heterozygous (+/p) mice. The titers of virus produced in the livers were 50- to 100-fold lower in p/p mice than in +/p or +/+ mice. p/p mice survived a dose 100-fold higher than the lethal dose of virus for +/+ mice. +/p mice were intermediate between +/+ and p/p mice in susceptibility to liver damage, virus growth in liver, and susceptibility to killing by MHV. Ceacam1a-targeted mice provide a new model to study the effects of modulation of receptor expression on susceptibility to MHV infection in vivo.

Soluble isoforms of CEACAM1 containing the A2 domain: increased serum levels in patients with obstructive jaundice and differences in 3-fucosyl-N-acetyl-lactosamine moiety.

CEACAM1 (biliary glycoprotein or CD66a) is a member of the carcinoembryonic antigen (CEA) subgroup of the CEA family. Eleven RNA isoforms derived from the splicing of a single CEACAM1 gene have been described. Some of the CEACAM1 isoforms have been recognized by the CD66 antibodies in T and B lymphocytes, natural killer cells, granulocytes and epithelial cells in several human tissues. Although it is also present in soluble form in bile and serum, and elevated levels have been found in the serum of patients with liver diseases, it is not known which isoforms are primarily involved. In order to learn more about the distribution and properties of particular CEACAM1 isoforms, we have prepared a monoclonal antibody specific for the A2 domain of CEACAM1, designated TEC-11. This antibody does not cross-react with other members of the CEA family. Immunoblotting analysis revealed that the TEC-11 epitope was present in all cell types expressing CEACAM1 containing the A2 domain [CEACAM1(A2)], including granulocytes (160 000 MW isoform) and sperm cells (140 000 MW isoform). A 115 000 MW isoform of CEACAM1(A2) was present in human serum, bile, saliva and seminal fluid. Human bile, saliva and seminal fluid also contained the 160 000 MW CEACAM1(A2) isoform. Significantly higher serum levels of the 115 000 MW CEACAM1(A2) isoform were detected in patients with obstructive jaundice. The 160 000 MW isoform of CEACAM1(A2) in bile, but not a 115 000 MW isoform in serum and bile, carried the 3-fucosyl-N-acetyl-lactosamine moiety. The combined data indicate that various isoforms of CEACAM1(A2) are present in different body fluids where they could take part in different CEACAM1-mediated functions.