Syntenin-1 is a molecule linking syndecan-mediated signaling to the cytoskeleton. Syntenin-1 is primarily localized to membrane-associated adherens junctions and focal adhesions but also found at the endoplasmic reticulum and nucleus. The syntenin protein contains tandemly repeated PDZ domains that bind the cytoplasmic, C-terminal domains of a variety of transmembrane proteins. Syntenin-1 may affect cytoskeletal-membrane organization, cell adhesion, protein trafficking, and the activation of transcription factors. It seems to function as an adapter protein, in adherens junctions may function to couple syndecans to cytoskeletal proteins or signaling components. Syntenin-1 seems to couple transcription factor SOX4 to the IL-5 receptor (IL5RA) and play a role in vesicular trafficking.