Expression cloning of a human polysialyltransferase that forms the polysialylated neural cell adhesion molecule present in embryonic brain.

Polysialic acid is a developmentally regulated posttranslational modification of the neural cell adhesion molecule (N-CAM). It has been suggested that this large anionic carbohydrate modulates the adhesive property of N-CAM, but the precise function of polysialic acid is not known. Here we describe the isolation and functional expression of a cDNA encoding a human polysialyltransferase. For this expression cloning, COS-1 cells were cotransfected with a human fetal brain cDNA library and a cDNA encoding human N-CAM. Transfected COS-1 cells were stained with a monoclonal antibody specific for polysialic acid and enriched by fluorescence-activated cell sorting. Sibling selection of recovered plasmids resulted in a cDNA clone that directs the expression of polysialic acid on the cell surface. The deduced amino acid sequence indicates that the polysialyltransferase shares a common sequence motif with other sialyltransferases cloned so far. The polysialyltransferase is, however, distinct by having two clusters of basic amino acids. The amount of the polysialyltransferase transcripts correlates well with the formation of polysialic acid in various human tissues, and is abundant in the fetal brain but not in the adult brain. Moreover, HeLa cells stably expressing polysialic acid and N-CAM promoted neurite outgrowth and sprouting. These results indicate that the cloned polysialyltransferase forms polysialylated, embryonic N-CAM, which is critical for plasticity of neural cells.

Interferon-gamma, interleukin-10, intercellular adhesion molecule-1, and chemokine receptor 5, but not interleukin-4, attenuate the development of periapical lesions

This study examines the role of Th1 (interferon-gamma [IFN-gamma]) and Th2 (interleukin-4 [IL-4] and IL-10) cytokines, an intercellular adhesion molecule (ICAM-1), and a chemokine receptor (CCR5) in the pathogenesis of periapical lesions at different stages of development in knockout mice. For lesion induction, the first molar was opened and inoculated with 4 bacterial strains and left open to the oral environment. After 21 and 42 days, the IFN-gamma, IL-10, ICAM-1, and CCR5 knockout animals presented periapical lesions larger than those of wild-type animals. There was no statistically significant difference between periapical lesions induced in IL-4 knockout and wild-type animals during the periods evaluated. Our findings suggest an important role for IFN-gamma, IL-10, ICAM-1, and CCR5 in the pathogenesis of experimentally induced pulp infection and bone destruction as endogenous suppressor of periapical lesion development, whereas IL-4 appears to present a nonsignificant effect on periapical lesion modulation.

Characterization of a human synovial cell antigen: VCAM-1 and inflammatory arthritis

The contribution of synovial cells to the pathogenesis of rheumatoid arthritis (RA) is only partly understood. Monoclonal antibody (mAb) 1D5 is one of very few mAb ever raised against RA synovial cells in order to study the biology of these cells. Studies on the expression pattern and structural features of the 1D5 Ag suggest that 1D5 recognizes human vascular cell adhesion molecule-1 (VCAM-1), which is an intercellular adhesion molecule. Vascular cell adhesion molecule-1 may be involved in a number of crucial intercellular interactions in RA.

INSULIN REGULATES CYTOKINES AND INTERCELLULAR ADHESION MOLECULE-1 GENE EXPRESSION THROUGH NUCLEAR FACTOR-kappa B ACTIVATION IN LPS-INDUCED ACUTE LUNG INJURY IN RATS

Diabetic patients have increased susceptibility to infection, which may be related to impaired inflammatory response observed in experimental models of diabetes, and restored by insulin treatment. The goal of this study was to investigate whether insulin regulates transcription of cytokines and intercellular adhesion molecule 1 (ICAM-1) via nuclear factor-kappa B (NF-kappa B) signaling pathway in Escherichia coli LIPS-induced lung inflammation. Diabetic male Wistar rats (alloxan, 42 mg/kg, iv., 10 days) and controls were instilled intratracheally with saline containing LPS (750 mu g/0.4 mL) or saline only. Some diabetic rats were given neutral protamine Hagedorn insulin (4 IU, s.c.) 2 h before LIPS. Analyses performed 6 h after LPS included: (a) lung and mesenteric lymph node IL-1 beta, TNF-alpha, IL-10, and ICAM-1 messenger RNA (mRNA) were quantified by real-time reverse transcriptase-polymerase chain reaction; (b) number of neutrophils in the bronchoalveolar lavage (BAL) fluid, and concentrations of IL-1 beta, TNF-alpha, and IL-10 in the BAL were determined by the enzyme-linked immunosorbent assay; and (c) activation of NF-kappa B p65 subunit and phosphorylation of I-kappa B alpha were quantified by Western blot analysis. Relative to controls, diabetic rats exhibited a reduction in lung and mesenteric lymph node IL-1 beta (40%), TNF-alpha (similar to 30%), and IL-10 (similar to 40%) mRNA levels and reduced concentrations of IL-1 beta (52%), TNF-alpha (62%), IL-10 (43%), and neutrophil counts (72%) in the BAL. Activation of NF-kappa B p65 subunit and phosphorylation of I-kappa B alpha were almost suppressed in diabetic rats. Treatment of diabetic rats with insulin completely restored mRNA and protein levels of these cytokines and potentiated lung ICAM-1 mRNA levels (30%) and number of neutrophils (72%) in the BAL. Activation of NF-kappa B p65 subunit and phosphorylation of I-kappa B alpha were partially restored by insulin treatment. In conclusion, data presented suggest that insulin regulates transcription of proinflammatory (IL-1 beta, TNF-alpha) and anti-inflammatory (IL-10) cytokines, and expression of ICAM-1 via the NF-kappa B signaling pathway.

Chemosensitization of carcinoma cells using epithelial cell adhesion molecule-targeted liposomal antisense against bcl-2/bcl-xL

Nanoscale drug delivery systems, such as sterically stabilized immunoliposomes binding to internalizing tumor-associated antigens, can increase therapeutic efficacy and reduce toxicity to normal tissues compared with nontargeted liposomes. The epithelial cell adhesion molecule (EpCAM) is of interest as a ligand for targeted drug delivery because it is abundantly expressed in solid tumors but shows limited distribution in normal tissues. To generate EpCAM-specific immunoliposomes for targeted cancer therapy, the humanized single-chain Fv antibody fragment 4D5MOCB was covalently linked to the exterior of coated cationic liposomes. As anticancer agent, we encapsulated the previously described antisense oligonucleotide 4625 specific for both bcl-2 and bcl-xL. The EpCAM-targeted immunoliposomes (SIL25) showed specific binding to EpCAM-overexpressing tumor cells, with a 10- to 20-fold increase in binding compared with nontargeted control liposomes. No enhanced binding was observed on EpCAM-negative control cells. On cell binding, SIL25 was efficiently internalized by receptor-mediated endocytosis, ultimately leading to down-regulation of both bcl-2 and bcl-xL expression on both the mRNA and protein level, which resulted in enhanced tumor cell apoptosis. In combination experiments, the use of SIL25 led to a 2- to 5-fold sensitization of EpCAM-positive tumor cells of diverse origin to death induction by doxorubicin. Our data show the promise of EpCAM-specific drug delivery systems, such as antisense-loaded immunoliposomes, for targeted cancer therapy.

Antitumor activity of an epithelial cell adhesion molecule targeted nanovesicular drug delivery system

Site-specific delivery of anticancer agents to tumors represents a promising therapeutic strategy because it increases efficacy and reduces toxicity to normal tissues compared with untargeted drugs. Sterically stabilized immunoliposomes (SIL), guided by antibodies that specifically bind to well internalizing antigens on the tumor cell surface, are effective nanoscale delivery systems capable of accumulating large quantities of anticancer agents at the tumor site. The epithelial cell adhesion molecule (EpCAM) holds major promise as a target for antibody-based cancer therapy due to its abundant expression in many solid tumors and its limited distribution in normal tissues. We generated EpCAM-directed immunoliposomes by covalently coupling the humanized single-chain Fv antibody fragment 4D5MOCB to the surface of sterically stabilized liposomes loaded with the anticancer agent doxorubicin. In vitro, the doxorubicin-loaded immunoliposomes (SIL-Dox) showed efficient cell binding and internalization and were significantly more cytotoxic against EpCAM-positive tumor cells than nontargeted liposomes (SL-Dox). In athymic mice bearing established human tumor xenografts, pharmacokinetic and biodistribution analysis of SIL-Dox revealed long circulation times in the blood with a half-life of 11 h and effective time-dependent tumor localization, resulting in up to 15% injected dose per gram tissue. These favorable pharmacokinetic properties translated into potent antitumor activity, which resulted in significant growth inhibition (compared with control mice), and was more pronounced than that of doxorubicin alone and nontargeted SL-Dox at low, nontoxic doses. Our data show the promise of EpCAM-directed nanovesicular drug delivery for targeted therapy of solid tumors.

Alterations in cell adhesion and migration are transcriptionally regulated by the tumor suppressor, TP53

The p53 transcription factor is a tumor suppressor and a master regulator of apoptosis and the cell cycle in response to cell stress. In some advanced tumors, such as prostate cancers, the loss of p53 correlates with an increase in the occurrence of metastases. In addition, several groups have suggested that p53 status correlates with changes in cell migration and cell morphology associated with a migratory phenotype. Others have identified several genes with roles in cell migration that are directly transcriptionally regulated by p53. Even so, modulation of cell migration is not widely recognized as a p53 stress response. ^ In an effort to identify novel p53 target genes and expand our knowledge of the p53 transcriptional response, we performed Affymetrix gene expression analysis in p53-null PC3 prostate cancer cells following infection with a control virus or adenoviral construct expressing wild-type p53. Over 300 genes that had not been previously recognized as p53 target genes were identified. Of these genes, 224 were upregulated and 111 were downregulated (p<0.05). Functional over-representation analysis identified cell migration as a significantly over-represented biological function of p53. Further analysis identified two genes that are critical for the control of cell migration as potential p53 targets. One, hyaluronan mediated motility receptor (HMMR), has recently been shown to be a p53 target important for regulation of the cell cycle. Here, we show that HMMR is downregulated by p53 in several cell lines, and HMMR's regulation is dependent on the presence of the cdk inhibitor, p21, and histone deactelyase activity. The other gene, carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), itself a tumor suppressor, is shown here, for the first time, as a p53 direct target by ChIP analysis. We next determined the effect of p53 activation on cell migration and found that p53 significantly slows the rate of cell migration in Boyden chamber migration assays and digital videomicroscopy wound healing studies. Further, our studies established the specific roles of CEACAM1 and HMMR in cell migration and determine that loss of CEACAM1 and overexpression of HMMR independently contribute to increased cell migration. Taken together, these studies provide a direct mechanistic link between p53 to the regulatory control of specific target genes that mediate cell adhesion and migration. ^

Optimal selectin-mediated rolling of leukocytes during inflammation in vivo requires intercellular adhesion molecule-1 expression

Leukocyte interactions with vascular endothelium during inflammation occur through discrete steps involving selectin-mediated leukocyte rolling and subsequent firm adhesion mediated by members of the integrin and Ig families of adhesion molecules. To identify functional synergy between selectin and Ig family members, mice deficient in both L-selectin and intercellular adhesion molecule 1 (ICAM-1) were generated. Leukocyte rolling velocities in cremaster muscle venules were increased significantly in ICAM-1-deficient mice during both trauma- and tumor necrosis factor α-induced inflammation, but rolling leukocyte flux was not reduced. Elimination of ICAM-1 expression in L-selectin-deficient mice resulted in a sharp reduction in the flux of rolling leukocytes during tumor necrosis factor α-induced inflammation. The observed differences in leukocyte rolling behavior demonstrated that ICAM-1 expression was required for optimal P- and L-selectin-mediated rolling. Increased leukocyte rolling velocities presumably translated into decreased tissue emigration because circulating neutrophil, monocyte, and lymphocyte numbers were increased markedly in L-selectin/ICAM-1-deficient mice. Furthermore, neutrophil emigration during acute peritonitis was reduced by 80% in the double-deficient mice compared with either L-selectin or ICAM-1-deficient mice. Thus, members of the selectin and Ig families function synergistically to mediate optimal leukocyte rolling in vivo, which is essential for the generation of effective inflammatory responses.

Long-term but not short-term plasticity at mossy fiber synapses is impaired in neural cell adhesion molecule-deficient mice

Cell adhesion molecules (CAMs) are known to be involved in a variety of developmental processes that play key roles in the establishment of synaptic connectivity during embryonic development, but recent evidence implicates the same molecules in synaptic plasticity of the adult. In the present study, we have used neural CAM (NCAM)-deficient mice, which have learning and behavioral deficits, to evaluate NCAM function in the hippocampal mossy fiber system. Morphological studies demonstrated that fasciculation and laminar growth of mossy fibers were strongly affected, leading to innervation of CA3 pyramidal cells at ectopic sites, whereas individual mossy fiber boutons appeared normal. Electrophysiological recordings performed in hippocampal slice preparations revealed that both basal synaptic transmission and two forms of short-term plasticity, i.e., paired-pulse facilitation and frequency facilitation, were normal in mice lacking all forms of NCAM. However, long-term potentiation of glutamatergic excitatory synapses after brief trains of repetitive stimulation was abolished. Taken together, these results strongly suggest that in the hippocampal mossy fiber system, NCAM is essential both for correct axonal growth and synaptogenesis and for long-term changes in synaptic strength.

Defining Extracellular Integrin α-Chain Sites That Affect Cell Adhesion and Adhesion Strengthening without Altering Soluble Ligand Binding

It was previously shown that mutations of integrin α4 chain sites, within putative EF-hand-type divalent cation-binding domains, each caused a marked reduction in α4β1-dependent cell adhesion. Some reports have suggested that α-chain “EF-hand” sites may interact directly with ligands. However, we show here that mutations of three different α4 “EF-hand” sites each had no effect on binding of soluble monovalent or bivalent vascular cell adhesion molecule 1 whether measured indirectly or directly. Furthermore, these mutations had minimal effect on α4β1-dependent cell tethering to vascular cell adhesion molecule 1 under shear. However, EF-hand mutants did show severe impairments in cellular resistance to detachment under shear flow. Thus, mutation of integrin α4 “EF-hand-like” sites may impair 1) static cell adhesion and 2) adhesion strengthening under shear flow by a mechanism that does not involve alterations of initial ligand binding.

Activation of transcription factor AP-2 mediates UVA radiation- and singlet oxygen-induced expression of the human intercellular adhesion molecule 1 gene

UVA radiation is the major component of the UV solar spectrum that reaches the earth, and the therapeutic application of UVA radiation is increasing in medicine. Analysis of the cellular effects of UVA radiation has revealed that exposure of human cells to UVA radiation at physiological doses leads to increased gene expression and that this UVA response is primarily mediated through the generation of singlet oxygen. In this study, the mechanisms by which UVA radiation induces transcriptional activation of the human intercellular adhesion molecule 1 (ICAM-1) were examined. UVA radiation was capable of inducing activation of the human ICAM-1 promoter and increasing ICAM-1 mRNA and protein expression. These UVA radiation effects were inhibited by singlet oxygen quenchers, augmented by enhancement of singlet oxygen life-time, and mimicked in unirradiated cells by a singlet oxygen-generating system. UVA radiation as well as singlet oxygen-induced ICAM-1 promoter activation required activation of the transcription factor AP-2. Accordingly, both stimuli activated AP-2, and deletion of the putative AP-2-binding site abrogated ICAM-1 promoter activation in this system. This study identified the AP-2 site as the UVA radiation- and singlet oxygen-responsive element of the human ICAM-1 gene. The capacity of UVA radiation and/or singlet oxygen to induce human gene expression through activation of AP-2 indicates a previously unrecognized role of this transcription factor in the mammalian stress response.

Identification of a Plasmodium falciparum intercellular adhesion molecule-1 binding domain: A parasite adhesion trait implicated in cerebral malaria

Binding of infected erythrocytes to brain venules is a central pathogenic event in the lethal malaria disease complication, cerebral malaria. The only parasite adhesion trait linked to cerebral sequestration is binding to intercellular adhesion molecule-1 (ICAM-1). In this report, we show that Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) binds ICAM-1. We have cloned and expressed PfEMP1 recombinant proteins from the A4tres parasite. Using heterologous expression in mammalian cells, the minimal ICAM-1 binding domain was a complex domain consisting of the second Duffy binding-like (DBL) domain and the C2 domain. Constructs that contained either domain alone did not bind ICAM-1. Based on phylogenetic criteria, there are five distinct PfEMP1 DBL types designated α, β, γ, δ, and ɛ. The DBL domain from the A4tres that binds ICAM-1 is DBLβ type. A PfEMP1 cloned from a distinct ICAM-1 binding variant, the A4 parasite, contains a DBLβ domain and a C2 domain in tandem arrangement similar to the A4tres PfEMP1. Anti-PfEMP1 antisera implicate the DBLβ domain from A4var PfEMP1 in ICAM-1 adhesion. The identification of a P. falciparum ICAM-1 binding domain may clarify mechanisms responsible for the pathogenesis of cerebral malaria and lead to interventions or vaccines that reduce malarial disease.

A binding site for homeodomain and Pax proteins is necessary for L1 cell adhesion molecule gene expression by Pax-6 and bone morphogenetic proteins

The cell adhesion molecule L1 regulates axonal guidance and fasciculation during development. We previously identified the regulatory region of the L1 gene and showed that it was sufficient for establishing the neural pattern of L1 expression in transgenic mice. In the present study, we characterize a DNA element within this region called the HPD that contains binding motifs for both homeodomain and Pax proteins and responds to signals from bone morphogenetic proteins (BMPs). An ATTA sequence within the core of the HPD was required for binding to the homeodomain protein Barx2 while a separate paired domain recognition motif was necessary for binding to Pax-6. In cellular transfection experiments, L1-luciferase reporter constructs containing the HPD were activated an average of 4-fold by Pax-6 in N2A cells and 5-fold by BMP-2 and BMP-4 in Ng108 cells. Both of these responses were eliminated on deletion of the HPD from L1 constructs. In transgenic mice, deletion of the HPD from an L1-lacZ reporter resulted in a loss of β-galactosidase expression in the telencephalon and mesencephalon. Collectively, our experiments indicate that the HPD regulates L1 expression in neural tissues via homeodomain and Pax proteins and is likely to be a target of BMP signaling during development.