TgrC1 mediates cell-cell adhesion by interacting with TgrB1 via mutual IPT/TIG domains during development of Dictyostelium discoideum

Cell-cell adhesion plays crucial roles in cell differentiation and morphogenesis during development of Dictyostelium discoideum. The heterophilic adhesion protein TgrC1 is expressed during cell aggregation and disruption of the tgrC1 gene results in the arrest of development at the loose aggregate stage. We have used far western blot coupled with mass spectrometry to identify TgrB1 as the heterophilic binding partner of TgrC1. Co-immunoprecipitation and pull-down studies showed that TgrB1 and TgrC1 are capable of binding with each other in solution. TgrB1 and TgrC1 are encoded by a pair of adjacent genes which share a common promoter. Both TgrB1 and TgrC1 are type I transmembrane proteins, which contain three extracellular IPT/TIG domains. Antibodies raised against TgrB1 inhibit cell reassociation at the post-aggregation stage of development and block fruiting body formation. Ectopic expression of TgrB1 and TgrC1 driven by the actin 15 promoter leads to heterotypic cell aggregation of vegetative cells. Using recombinant proteins that cover different portions of TgrB1 and TgrC1 in binding assays, we have mapped the cell binding regions in these two proteins to K537-A783 in TgrB1 and I336-V360 in TgrC1, corresponding to their respective TIG3 and TIG2 domain.

Source: BJ Cell - March 12, 2013 Category: Biochemistry Authors: G Chen, J Wang, X Xu, X Wu, R Piao, C Siu Tags: BJ Cell Source Type: research