Acts as a ligand for the urokinase plasminogen activator surface receptor. Plays a role in angiogenesis by inducing endothelial cell migration and the formation of vascular network (cords). Involved in cellular migration and adhesion. Increases the phosphorylation levels of FAK. Interacts with and increases the mitogenic activity of HGF. Promotes synapse formation. May have a role in the perisylvian region, critical for language and cognitive development. {ECO:0000269|PubMed:16497722, ECO:0000269|PubMed:18718938, ECO:0000269|PubMed:19065654, ECO:0000269|PubMed:24179158}. This is the function of Ensembl gene identifier ENSG00000102359 (SRPX2, sushi repeat containing protein X-linked 2).