The membrane glycoprotein gp150 is encoded by the lagC gene and mediates cell-cell adhesion by heterophilic binding during Dictyostelium development

gp150 is a membrane glycoprotein which has been implicated in cell-cell adhesion in the postaggregation stages of Dictyostelium development. An analysis of its tryptic peptides by mass spectrometry has identified gp150 as the product of the lagC gene, which was previously shown to play a role in morphogenesis and cell-type specification. Antibodies raised against the GST-LagC fusion protein specifically recognized gp150 in wild-type cells and showed that it is missing in lagC-null cells. Immunolocalization studies have confirmed its enrichment in cell- cell contact regions. In mutant cells that lack the aggregation stage-specific cell adhesion molecule gp80, gp150 is expressed precociously. Moreover, these cells acquire EDTA-resistant cell-cell binding during aggregation, suggesting a role for gp150 in this process. Cells in which the genes encoding gp80 and gp150 are both inactivated do not acquire EDTA-resistant cell adhesion during aggregation. Strains transformed with an actin 15::lagC construct express gp150 precociously, but do not show EDTA-resistant adhesion during early development. However, vegetative cells expressing gp150 can be recruited into aggregates of 16-h lagC-null cells. These results, together with those obtained with the cell-to-substratum binding assay, indicate that gp150 mediates cell-cell adhesion via heterophilic interactions with another component that accumulates during the aggregation stage. (C) 2000 Academic Press.