Proposed model of the EphB1-Caskin1 interaction. Ligand-activated EphB1 recruits the adaptor protein Nck through the phosphorylated Y594 residue. In turn, Nck forms a complex with Caskin1 via the SH3 domains of Nck. Recruitment of Caskin1 to the vicinity of the receptor leads to the phosphorylation of the Caskin1 SH3 domain on tyrosine residues 296 and 336. Tyrosine phosphorylated Caskin1 then likely promotes reorganization of the actin cytoskeleton leading to spine formation. PDZ, (p ostsynaptic density 95, PSD-85; discs large, D lg; zonula occludens-1, Z O-1), SH2, Src-homology domain 2, SH3, Src-homology domain 3, SAM, sterile alpha motif.