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Monoclonal antibodies block cell-cell adhesion in Dictyostelium discoideum
Abstract:
Of 39 monoclonal antibodies that bind the cell surface of aggregating Dictyostelium discoideum, 4 block 76-98% of cell-cell adhesion measured in an in vitro assay. The active antibodies all bind in the range of 10(6) antigenic sites/cell surface and react with more than one material on nitrocellulose blots prepared after polyacrylamide gel electrophoresis of whole aggregating cells in sodium dodecyl sulfate. Active antibodies can by grouped into two classes, each with two very similar members. Class I binds several molecules that are prominent in aggregating cells but scarce or undetectable in vegetative cells, blocks cell adhesion only in the presence of EDTA, and has no detectable effect on cell morphology. Class II binds a wide range of molecules present in both vegetative and aggregating cells, inhibits adhesion as well in the absence as in the presence of EDTA, and reversibly alters cell shape.
Insights
Four monoclonal antibodies effectively block cell-cell adhesion in Dictyostelium discoideum. These antibodies target distinct cell surface molecules, with two classes showing varied effects on adhesion and cell shape.
Area of Science:
- Cell Biology
- Biochemistry
- Developmental Biology
Background:
- Dictyostelium discoideum undergoes aggregation for multicellular development.
- Cell-cell adhesion is crucial for this aggregation process.
- Understanding the molecular basis of adhesion is key to deciphering developmental mechanisms.
Purpose of the Study:
- To identify and characterize monoclonal antibodies that inhibit Dictyostelium discoideum cell-cell adhesion.
- To investigate the molecular targets of these adhesion-blocking antibodies.
- To differentiate antibody classes based on their binding properties and effects.
Main Methods:
- Screening of 39 monoclonal antibodies for inhibition of cell-cell adhesion in vitro.
- Quantification of antigenic sites per cell surface.
- Analysis of antibody reactivity with cell surface molecules using SDS-PAGE and nitrocellulose blotting.
- Assessment of antibody effects on cell adhesion in the presence and absence of EDTA.
- Observation of antibody-induced changes in cell morphology.
Main Results:
- Four out of 39 antibodies significantly blocked cell-cell adhesion (76-98%).
- Active antibodies bound approximately 10^6 antigenic sites/cell and reacted with multiple proteins.
- Antibodies were classified into two groups: Class I and Class II.
- Class I antibodies blocked adhesion with EDTA and targeted aggregation-specific molecules.
- Class II antibodies blocked adhesion with or without EDTA, affected various molecules, and altered cell shape reversibly.
Conclusions:
- Specific monoclonal antibodies can effectively inhibit Dictyostelium discoideum cell-cell adhesion.
- Adhesion involves multiple cell surface molecules, targeted by different antibody classes.
- Two distinct mechanisms or molecular players in cell adhesion are suggested by the antibody classifications.