Intercellular adhesion in the cellular slime mold Polysphondylium pallidum.

Evidence is reviewed involving two classes of contact sites in intercellular adhesion of the cellular slime mold P. pallidum. Characterization and purification of the contact sites by using an immunological approach have led to the identification of a dimerizing glycoprotein as the major component mediating cell adhesion. Monoclonal antibodies have confirmed its localization on the cell surface of both growth phase and aggregation competent cells. A second component, which is developmentally regulated, has been partially purified. In an independent approach, plasma membrane factors which directly affect cell adhesion have been extracted and their relationship with the immunologically defined contact sites studied. The involvement of these different adhesion factors in regulating species-specific intercellular adhesion was investigated in cell sorting out experiments. It was shown that species-specific intercellular adhesion is mediated by the developmentally regulated contact sites.