Characterization of the beta-dystroglycan-growth factor receptor 2 (Grb2) interaction

The beta-dystroglycan/Grb2 interaction was investigated and a proline-rich region within beta-dystroglycan that binds Grb2-src homology 3 domains iden tified. We used surface plasmon resonance (SPR), fluorescence analysis, and solid-phase binding assay to measure the affinity constants between Grb2 a nd the beta-dystroglycan cytoplasmic tail. Analysis of the data obtained fr om SPR reveals a high-affinity interaction (K-D approximate to 240 nM) betw een Grb2 and the last 20 amino acids of the beta-dystroglycan carboxyl-term inus, which also contains a dystrophin-binding site. A similar K-D value (K -D approximate to 280 nM) was obtained by solid-phase binding assay and in solution by fluorescence. Both Grb2-SH3 domains bind beta-dystroglycan but the N-terminal SH3 domain binds with an affinity approximately fourfold hig her than that of the C-terminal SH3 domain. The Grb2-beta-dystroglycan inte raction was inhibited by dystrophin in a range of concentration of 160-400 nM. These data suggest a highly regulated and dynamic dystrophin/dystroglyc an complex formation and that this complex is involved in cell signaling. ( C) 2000 Academic Press.