Association between MAG and β1-integrin in primary hippocampal neurons. A. Sequence alignment of the RGD motif in the F-strand of MAG (Siglec-4) and SnD1 (Siglec-1) from different species. B-E. Association between MAG and β1-integrin. Primary hippocampal cultures were treated with wild-type MAG-Fc (RGD), mutant MAG-Fc (KGE), or native Fc fragment, in the presence or absence of echistatin (100 nM) or Ha2/5 (0.5 or 2.0 μg/ml). Cell lysates were immunoprecipitated with antibodies raised against β1-integrin and subjected to immunobloting for human Fc fragment, or vice versa (B, C, E). In GST pull-down experiments (D), purified GST-β1-integrin (extracellular domain) or GST control was incubated with MAG-Fc or native Fc fragment, and GST pull-down was subjected to western blot analysis and immunobloting for the Fc fragment.