title: Selective elimination of the contact site A protein of Dictyostelium discoideum by gene disruption.
abstract: The contact site A glycoprotein is a developmentally regulated cell-surface component expressed during the aggregation stage of Dictyostelium discoideum. This protein has been implicated in the EDTA-stable (Ca2(+)-independent) type of cell adhesion of aggregating cells. The gene coding for the contact site A protein was disrupted by homologous recombination, using a transformation vector that contained a 1.0-kb cDNA fragment as an insert. Transformants that did not express the protein were identified by colony immunoblotting. These transformants produced three truncated contact site A transcripts. One of them was controlled by the original contact site A promoter, as indicated by its strict developmental regulation and cAMP inducibility; the other two transcripts were transcribed from the actin 6 promoter of the vector. When cell adhesion was assayed in the transformants by agitating suspended cells in an agglutinometer, EDTA-stable adhesion was drastically reduced as compared to wild type, confirming that the contact site A glycoprotein acts as a cell-adhesion molecule. However, aggregation of the transformed cells on an agar surface was not remarkably altered. These results suggest that the contact site A glycoprotein is responsible for a 'fast' type of cell adhesion that is essential when aggregating cells are subjected to shear. When cells are not mechanically disturbed, a 'slow' type of adhesion mediated by other molecules is sufficient for their aggregation.
authors.affiliation: Max-Planck-Institut für Biochemie, Martinsried bei München, Federal Republic of Germany.
authors.forename: C
authors.initials: C
authors.lastname: Harloff
authors.forename: G
authors.initials: G
authors.lastname: Gerisch
authors.forename: A A
authors.initials: AA
authors.lastname: Noegel
mesh_terms: D015152:Blotting, Northern; D015139:Blotting, Southern; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D004023:Dictyostelium / Q000235:genetics* / Q000502:physiology; D004492:Edetic Acid / Q000494:pharmacology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D015800:Protozoan Proteins; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014170:Transformation, Genetic
chemical_list: D015815:Cell Adhesion Molecules; D005656:Fungal Proteins; D006023:Glycoproteins; D015800:Protozoan Proteins; C052291:cell cohesion molecule, Dictyostelium; D004492:Edetic Acid