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The contact site A glycoprotein mediates cell-cell adhesion by homophilic binding in Dictyostelium discoideum.
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MedLine Citation:
PMID:  3320049     Owner:  NLM     Status:  MEDLINE    
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.
C H Siu; A Cho; A H Choi
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of cell biology     Volume:  105     ISSN:  0021-9525     ISO Abbreviation:  J. Cell Biol.     Publication Date:  1987 Dec 
Date Detail:
Created Date:  1988-02-05     Completed Date:  1988-02-05     Revised Date:  2010-09-09    
Medline Journal Info:
Nlm Unique ID:  0375356     Medline TA:  J Cell Biol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2523-33     Citation Subset:  IM    
Banting and Best Department of Medical Research, C.H. Best Institute, University of Toronto, Canada.
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MeSH Terms
Cell Membrane / ultrastructure
Dictyostelium / cytology*,  growth & development,  ultrastructure
Fluorescent Antibody Technique
Glycoproteins / isolation & purification,  physiology*
Microscopy, Electron, Scanning
Molecular Weight
Protein Binding
Reg. No./Substance:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Full Text
Journal Information
Journal ID (nlm-ta): J Cell Biol
ISSN: 0021-9525
ISSN: 1540-8140
Publisher: The Rockefeller University Press
Article Information
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Print publication date: Day: 1 Month: 12 Year: 1987
Volume: 105 Issue: 6
First Page: 2523 Last Page: 2533
ID: 2114711
Publisher Id: 88087386
PubMed Id: 3320049

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

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