scholarly journals Regulation of slug size by the cell adhesion molecule gp80 in Dictyostelium discoideum.

1990 ◽  
Vol 1 (10) ◽  
pp. 715-729 ◽  
Author(s):  
R K Kamboj ◽  
T Y Lam ◽  
C H Siu
Keyword(s):  
Dictyostelium Discoideum ◽  
Parental Strain ◽  
Physiological Role ◽  
Resistant Cell ◽  
Surface Glycoprotein ◽  
Cell Binding ◽  
Cell Surface Glycoprotein ◽  
Cell Cell

We previously provided in vitro evidence that the cell surface glycoprotein of Mr80,000 (gp80) of Dictyostelium discoideum is capable of mediating EDTA-resistant cell-cell binding. Expression of gp80 is specific for the aggregation stage when cells form tight aggregates. To investigate the physiological role of gp80, Dictyostelium cells were transformed with a vector containing gp80 cDNA fused to an actin promoter. gp80 transcripts were detected in transformed cells in their vegetative growth phase. Transformants at this stage also exhibited EDTA-resistant cell cohesion, thus providing direct in vivo evidence that gp80 mediates cell-cell binding via homophilic interaction. While aggregates of the parental strain KAX3 had the tendency to break up to form small slugs, transformants expressing an increased amount of gp80 were able to maintain the integrity of aggregates, giving rise to larger slugs, resulting in the formation of bigger fruiting bodies. To further demonstrate that the increase in slug size could be correlated with the expression of gp80, cells of the parental strain were treated with exogenous cAMP pulses to stimulate an over-expression of gp80. The treated cells also gave rise to larger slugs, consistent with the notion that slug size is influenced by intercellular adhesiveness during development.

scholarly journals A pharmacologically distinct cyclic AMP receptor is responsible for the regulation of gp80 expression in Dictyostelium discoideum.

1990 ◽  
Vol 10 (7) ◽  
pp. 3297-3306 ◽  
Author(s):  
P C Ma ◽  
C H Siu
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Dictyostelium Discoideum ◽  
Surface Glycoprotein ◽  
Intracellular Camp ◽  
Cell Surface Glycoprotein ◽  
Cyclase Activation ◽  
Adenylate Cyclase Activation ◽  
Camp Receptor

The EDTA-resistant cell-cell adhesion expressed at the aggregation stage of Dictyostelium discoideum is mediated by a cell surface glycoprotein of Mr 80,000 (gp80). The expression of gp80 is developmentally regulated by cyclic AMP (cAMP). In vitro nuclear run-on experiments show that transcription of the gp80 gene is initiated soon after the onset of development. The basal level of gp80 transcription is significantly augmented by exogenous cAMP pulses. Interestingly, in analog studies, 2'-deoxy-cAMP, 8-bromo-cAMP, and N6-monobutyryl-cAMP are all capable of inducing a rapid accumulation of gp80 mRNA, suggesting the presence of a unique cAMP receptor that responds equally well to these analogs. To determine whether intracellular cAMP plays a role in the regulation of gp80 expression, caffeine was used to block cAMP-induced receptor-mediated adenylate cyclase activation. Expression of gp80 mRNA was blocked in caffeine-treated cells but could be substantially restored by treatment with exogenous cAMP pulses, suggesting that adenylate cyclase activation is not required. gp80 expression was also examined in the signal transduction mutants synag 7 and frigid A. In both mutants, gp80 was expressed at the basal level. Pulses of cAMP as well as 2'-deoxy-cAMP and N6-monobutyryl-cAMP were capable of restoring the normal level of gp80 expression in synag 7 cells. These results, taken together, indicate bimodal regulation of gp80 expression during development and the involvement of a novel cAMP receptor in the transmembrane signalling pathway that regulates gp80 gene expression.

C-CAM (cell-CAM 105) is an adhesive cell surface glycoprotein with homophilic binding properties

1990 ◽  
Vol 96 (1) ◽  
pp. 17-25
Author(s):  
A. Tingstrom ◽  
I. Blikstad ◽  
M. Aurivillius ◽  
B. Obrink
Keyword(s):  
Cell Adhesion ◽  
Cell Surface ◽  
Surface Glycoprotein ◽  
Membrane Glycoproteins ◽  
Binding Properties ◽  
Homophilic Binding ◽  
Cell Surface Glycoprotein ◽  
Fab Fragments ◽  
Cell Cell

C-CAM (Cell-CAM 105) is a cell surface glycoprotein that is involved in cell-cell adhesion of rat hepatocytes in vitro. To elucidate the adhesion mechanism the binding properties of purified C-CAM were investigated. Using proteins immobilized on nitrocellulose it was found that radiolabeled C-CAM bound to C-CAM but not to a variety of other proteins. Partitioning in Triton X-114 showed that C-CAM has hydrophobic properties. In accordance with this, C-CAM was effectively incorporated into phosphatidylcholine liposomes by dialysis from octylglucoside-containing solutions. The C-CAM-containing liposomes bound specifically to isolated hepatocytes. This binding was blocked by Fab fragments of anti-C-CAM antibodies. Furthermore, preincubation of hepatocytes with anti-C-CAM antibodies followed by washing of the cells blocked binding of C-CAM-containing liposomes. At increasing C-CAM contents in the reconstituted liposomes a marked self-aggregation of the liposomes occurred. This aggregation was blocked by Fab fragments of anti-C-CAM antibodies and by alkaline pH. After neutralization a rapid reaggregation occurred. Neither C-CAM binding to C-CAM immobilized on nitrocellulose nor C-CAM-liposome aggregation required calcium ions. Liposomes reconstituted with C-CAM-depleted membrane glycoproteins did not self-aggregate or bind to hepatocytes. Thus, it is concluded that C-CAM can bind specifically to C-CAM in a homophilic binding reaction that does not require calcium. Accordingly, C-CAM has the potential of directly mediating cell-cell adhesion via C-CAM-C-CAM binding between adjacent cells.

scholarly journals Galectin–glycan lattices regulate cell-surface glycoprotein organization and signalling

2008 ◽  
Vol 36 (6) ◽  
pp. 1472-1477 ◽  
Author(s):  
Omai B. Garner ◽  
Linda G. Baum
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Targeted Delivery ◽  
Cell Types ◽  
Surface Glycoprotein ◽  
Membrane Domains ◽  
Cellular Functions ◽  
Cell Surface Glycoprotein

The formation of multivalent complexes of soluble galectins with glycoprotein receptors on the plasma membrane helps to organize glycoprotein assemblies on the surface of the cell. In some cell types, this formation of galectin–glycan lattices or scaffolds is critical for organizing plasma membrane domains, such as lipid rafts, or for targeted delivery of glycoproteins to the apical or basolateral surface. Galectin–glycan lattice formation is also involved in regulating the signalling threshold of some cell-surface glycoproteins, including T-cell receptors and growth factor receptors. Finally, galectin–glycan lattices can determine receptor residency time by inhibiting endocytosis of glycoprotein receptors from the cell surface, thus modulating the magnitude or duration of signalling from the cell surface. This paper reviews recent evidence in vitro and in vivo for critical physiological and cellular functions that are regulated by galectin–glycoprotein interactions.

A6 Peptide Is Selectively Cytotoxic For Chronic Lymphocytic Leukemia Cells

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 5303-5303
Author(s):  
Suping Zhang ◽  
Hsien Lai ◽  
Grace Liu ◽  
Laura Rassenti ◽  
Michael Y. Choi ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Lymphocytic Leukemia ◽  
Surface Glycoprotein ◽  
Leukemia Cells ◽  
Dependent Manner ◽  
Cell Surface Glycoprotein

Abstract Chronic lymphocytic leukemia (CLL) cells express high levels of CD44, a cell-surface glycoprotein receptor for hyaluronic acid (HA). We found that a mAb specific for CD44 was directly cytotoxic for leukemia B cells, but had little effect on normal B cells. Moreover, this anti-CD44 mAb could induce CLL cells that expressed the zeta-associated protein of 70 kDa (ZAP-70) to undergo caspase-dependent apoptosis, independent of complement or cytotoxic effector cells (Proc Natl Acad Sci, USA 2013, PMID: 23530247). The cytotoxic effect of this mAb was not mitigated when the CLL cells were co-cultured with mesenchymal stromal cells (MSCs) or hyaluronic acid or when they were stimulated via ligation of the B-cell receptor with anti-µ. A6 (Angstrom Pharmaceuticals) is an 8-amino acid peptide that has marked homology with a linear sequence of CD44. A6 can bind CD44 within a region of the ligand-binding domain, leading to inhibition of the migration and metastatic potential of CD44-expressing cancer cells in vitro and in vivo (Mol Cancer Ther, 2011 PMID: 21885863). We evaluated the cytotoxic activity of A6 against primary leukemia cells of patients with CLL (n = 22). We found that A6 peptide also was directly cytotoxic for CLL cells isolated from different patients in a dose-dependent manner at concentrations that may be achieved in vivo. The A6 peptide appeared less cytotoxic for CLL cells than the intact anti-CD44 mAb, but still had greater direct cytotoxicity for CLL cells that expressed ZAP-70 than for CLL cells that were ZAP-70 negative. Furthermore, the A6 peptide had negligible effect on the viability of lymphocytes isolated from the blood of healthy donors (n = 3). Because clinical studies have found the A6 peptide to be well-tolerated and without dose-limiting toxicity in patients with solid tumors who have been treated to date (N = 40), a clinical study is planned to evaluate the safety and activity of the A6 peptide in the treatment of patients with CLL. Disclosures: Howell: Angstrom Phamaceuticals: Membership on an entity’s Board of Directors or advisory committees. Finlayson:Angstrom Phamaceuticals: Employment.

scholarly journals The contact site A glycoprotein mediates cell-cell adhesion by homophilic binding in Dictyostelium discoideum.

1987 ◽  
Vol 105 (6) ◽  
pp. 2523-2533 ◽  
Author(s):  
C H Siu ◽  
A Cho ◽  
A H Choi
Keyword(s):  
Monoclonal Antibody ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Dependent Manner ◽  
Cell Binding ◽  
Intact Cells ◽  
Cell Surface Glycoprotein ◽  
Stage Of Development ◽  
Homophilic Interaction ◽  
Cell Cell

Dictyostelium discoideum expresses a developmentally regulated cell surface glycoprotein of Mr 80,000 (gp80), which has been implicated in the formation of the EDTA-resistant contact sites A at the cell aggregation stage. To determine whether gp80 participates directly in cell binding and, if so, its mode of action, we conjugated purified gp80 to Covaspheres (Covalent Technology Corp., Ann Arbor, MI) and investigated their ability to bind to cells. The binding of gp80-Covaspheres was dependent on the developmental stage of the cells, with maximal interaction at the late aggregation stage. Scanning electron microscopic studies revealed the clustering of gp80-Covaspheres at the polar ends of these cells, similar to the pattern of gp80 distribution on the cell surface as reported earlier (Choi, A. H. C., and Siu, C.-H., 1987, J. Cell Biol., 104:1375-1387). Precoating cells with an adhesion-blocking anti-gp80 monoclonal antibody inhibited the binding of gp80-Covaspheres, suggesting that Covasphere-associated gp80 might undergo homophilic interaction with gp80 on the cell surface. Quantitative binding of 125I-labeled gp80 to intact cells gave an estimate of 1.5 X 10(5) binding sites per cell at the aggregation stage. Binding of soluble gp80 to cells was blocked by precoating cells with the anti-gp80 monoclonal antibody. The ability of gp80 to undergo homophilic interaction was further tested in a filter-binding assay, which showed that 125I-labeled gp80 was able to interact with gp80 bound on nitrocellulose in a dosage-dependent manner. In addition, reassociation of cells was significantly inhibited in the presence of soluble gp80, suggesting that gp80 has a single cell-binding site. These results are consistent with the notion that gp80 mediates cell-cell binding at the aggregation stage of development via homophilic interaction.

scholarly journals Involvement of cell-cell adhesion in the expression of the cell cohesion molecule gp80 in Dictyostelium discoideum

1994 ◽  
Vol 107 (6) ◽  
pp. 1705-1712 ◽  
Author(s):  
L. Desbarats ◽  
S.K. Brar ◽  
C.H. Siu
Keyword(s):  
Cell Adhesion ◽  
Dictyostelium Discoideum ◽  
Binding Sites ◽  
Signal Transduction Pathway ◽  
Resistant Cell ◽  
Cell Contact ◽  
Developmental Cycle ◽  
Sensitive Cell ◽  
Cell Binding ◽  
Cell Cell

Soon after the initiation of the developmental cycle of Dictyostelium discoideum, cells acquire EDTA-sensitive cell-cell binding sites mediated by the glycoprotein gp24. Cells at the aggregation stage display a second type of cell adhesion site, the EDTA-resistant cell-cell binding sites, mediated by the glycoprotein gp80. The gene encoding gp80 is first turned on to a low basal level of expression in the preaggregation stage. At the onset of the aggregation stage, cells produce pulses of low levels of cAMP, which greatly augment the expression of gp80. To investigate the role of cell-cell adhesion in the regulation of gp80 expression, cells were developed in the presence of EDTA or carnitine to block the EDTA-sensitive cell binding sites. Alternatively, cell cohesion was disrupted by shaking low-density cultures at high shearing forces. In all three instances, gp80 was expressed at a substantially reduced level. In addition, exogenous cAMP pulses, which normally were capable of stimulating a precocious and enhanced expression of gp80, failed to restore the high level of gp80 expression. However, if the formation of cell-cell contact was permitted, exogenous cAMP pulses were able to rescue the expression of gp80 even when the cAMP signal relay was blocked. These results indicate that previous cell-cell contact, provided by the EDTA-sensitive binding sites, is required for the activation of the cAMP-mediated signal transduction pathway producing high levels of gp80 expression.

scholarly journals Platelet PECAM-1 inhibits thrombus formation in vivo

Blood ◽  
2006 ◽  
Vol 107 (2) ◽  
pp. 535-541 ◽  
Author(s):  
Shahrokh Falati ◽  
Sonali Patil ◽  
Peter L. Gross ◽  
Michelle Stapleton ◽  
Glenn Merrill-Skoloff ◽  
...  
Keyword(s):  
Vascular Endothelial Cells ◽  
Thrombus Formation ◽  
Surface Glycoprotein ◽  
Vessel Occlusion ◽  
Cell Surface Glycoprotein ◽  
Platelet Endothelial Cell Adhesion ◽  
A Cell ◽  
Deficient Mice

AbstractPlatelet endothelial cell adhesion molecule-1 (PECAM-1) is a cell surface glycoprotein receptor expressed on a range of blood cells, including platelets, and on vascular endothelial cells. PECAM-1 possesses adhesive and signaling properties, the latter being mediated by immunoreceptor tyrosine-based inhibitory motifs present on the cytoplasmic tail of the protein. Recent studies in vitro have demonstrated that PECAM-1 signaling inhibits the aggregation of platelets. In the present study we have used PECAM-1–deficient mice and radiation chimeras to investigate the function of this receptor in the regulation of thrombus formation. Using intravital microscopy and laser-induced injury to cremaster muscle arterioles, we show that thrombi formed in PECAM-1–deficient mice were larger, formed more rapidly than in control mice, and were more stable. Larger thrombi were also formed in control mice that received transplants of PECAM-1–deficient bone marrow, in comparison to mice that received control transplants. A ferric chloride model of thrombosis was used to investigate thrombus formation in carotid arteries. In PECAM-1–deficient mice the time to 75% vessel occlusion was significantly shorter than in control mice. These data provide evidence for the involvement of platelet PECAM-1 in the negative regulation of thrombus formation.

A pharmacologically distinct cyclic AMP receptor is responsible for the regulation of gp80 expression in Dictyostelium discoideum

1990 ◽  
Vol 10 (7) ◽  
pp. 3297-3306
Author(s):  
P C Ma ◽  
C H Siu
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Dictyostelium Discoideum ◽  
Surface Glycoprotein ◽  
Intracellular Camp ◽  
Cell Surface Glycoprotein ◽  
Cyclase Activation ◽  
Adenylate Cyclase Activation ◽  
Camp Receptor

The EDTA-resistant cell-cell adhesion expressed at the aggregation stage of Dictyostelium discoideum is mediated by a cell surface glycoprotein of Mr 80,000 (gp80). The expression of gp80 is developmentally regulated by cyclic AMP (cAMP). In vitro nuclear run-on experiments show that transcription of the gp80 gene is initiated soon after the onset of development. The basal level of gp80 transcription is significantly augmented by exogenous cAMP pulses. Interestingly, in analog studies, 2'-deoxy-cAMP, 8-bromo-cAMP, and N6-monobutyryl-cAMP are all capable of inducing a rapid accumulation of gp80 mRNA, suggesting the presence of a unique cAMP receptor that responds equally well to these analogs. To determine whether intracellular cAMP plays a role in the regulation of gp80 expression, caffeine was used to block cAMP-induced receptor-mediated adenylate cyclase activation. Expression of gp80 mRNA was blocked in caffeine-treated cells but could be substantially restored by treatment with exogenous cAMP pulses, suggesting that adenylate cyclase activation is not required. gp80 expression was also examined in the signal transduction mutants synag 7 and frigid A. In both mutants, gp80 was expressed at the basal level. Pulses of cAMP as well as 2'-deoxy-cAMP and N6-monobutyryl-cAMP were capable of restoring the normal level of gp80 expression in synag 7 cells. These results, taken together, indicate bimodal regulation of gp80 expression during development and the involvement of a novel cAMP receptor in the transmembrane signalling pathway that regulates gp80 gene expression.

Molecular mechanisms of cell-cell interaction in Dictyostelium discoideum

1988 ◽  
Vol 66 (10) ◽  
pp. 1089-1099 ◽  
Author(s):  
Chi-Hung Siu ◽  
Lu Min Wong ◽  
Tak Yee Lam ◽  
Rajender K. Kamboj ◽  
Anthony Choi ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Binding Sites ◽  
Cell Binding ◽  
Cell Surface Glycoprotein ◽  
Stage Of Development ◽  
Tissue Organization ◽  
Surface Glycoproteins ◽  
Cell Cell

During development of the cellular slime mold Dictyostelium discoideum, cells migrate in respose to cAMP to form aggregates, which give rise to fruiting bodies consisting of two major cell types: spores and stalk cells. Multicellularity is achieved by the expression of two types of cell–cell adhesion sites. The EDTA-sensitive binding sites are expressed at the initial stage of development. At the aggregation stage, cells acquire EDTA-resistant binding sites, which are mediated by a cell-surface glycoprotein of Mr 80 000 (gp80). gp80 is preferentially associated with cell surface filopodia, which are probably involved in the initiation of contact formation between cells. Covaspheres conjugated with gp80 bind specifically to aggregation-stage cells. The binding can be inhibited by precoating cells with an anti-gp80 monoclonal antibody, thus suggesting that gp80 mediates cell-cell binding via homophilic interaction. The structure of gp80 predicted from its cDNA sequence can be divided into three major domains: a membrane anchor, a hinge, and a globular region. An analysis of fusion proteins containing different gp80 segments shows that the cell-binding activity resides in the globular region. In the postaggregation stages, gp80 is replaced by other surface glycoproteins in maintaining cell–cell adhesion. One of them has a Mr of 150 000 (gp150). Anti-gp150 antibodies have no effect on aggregation-stage cells, but they disrupt cell–cell adhesion at subsequent stages. It becomes evident that the complex phenomena of cell adhesion and tissue organization involve the participation of a number of surface glycoproteins.

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