Two distinct adhesion systems are responsible for EDTA-sensitive adhesion in Dictyostelium discoideum.
Early in their developmental program, Dictyostelium discoideum exhibit EDTA-sensitive and EDTA-resistant adhesion. The molecules which mediate the adhesions have been called contact sites, with contact sites A mediating EDTA-resistant adhesion and contact sites B mediating EDTA-sensitive adhesion. The studies described here have revealed that prior to aggregation, a second EDTA-sensitive adhesion system emerges. In keeping with previously established nomenclature, the molecules mediating the newly discovered adhesion system have been called contact sites C. Unlike contact sites B, contact sites C are unaffected by a contact sites B-blocking peptide. Contact sites C-mediated adhesion is also distinct from contact sites B-mediated adhesion in that contact sites C-mediated adhesion is EGTA-resistant and in the presence of EDTA it can be rescued by the addition of Mg2+. Thus Mg2+ may be the cation present under physiological conditions that is essential for contact sites C activity. Unlike contact sites B-mediated adhesion, contact sites C-mediated adhesion is not observed in growing amoebae. Contact sites C-mediated adhesion first becomes apparent within hours after the initiation of development and its strength appears to increase throughout the first 10 h of the developmental program. A mutant lacking the EDTA-resistant contact sites A exhibits normal contact sites B- and C-mediated adhesion, demonstrating that both EDTA-sensitive adhesion systems are independent of contact sites A. Thus aggregating D. discoideum amoebae possess three distinct adhesion systems, one of them is EDTA-resistant and the other two are EDTA-sensitive.
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Department of Microbiology, University of Minnesota, Minneapolis 55455.
D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000502:physiology*; D004023:Dictyostelium / Q000187:drug effects / Q000502:physiology*; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D005656:Fungal Proteins / Q000378:metabolism* / Q000502:physiology*; D006023:Glycoproteins / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D015800:Protozoan Proteins
D015815:Cell Adhesion Molecules; D005656:Fungal Proteins; C083465:GP24A protein, Dictyostelium discoideum; C083466:GP24B protein, Dictyostelium discoideum; D006023:Glycoproteins; D015800:Protozoan Proteins; C052291:cell cohesion molecule, Dictyostelium; D004533:Egtazic Acid; D004492:Edetic Acid; D008274:Magnesium