Laminin 5/laminin 332 (LN332) is an adhesion substrate for epithelial cells. After secretion of LN332, a regulated cleavage occurs at the carboxy‐terminus of its alpha3 subunit, which releases a tandem of two globular modules named LG4/5. We show that the presence of the LG4/5 domain in precursor LN332 decreases its integrin‐mediated cell adhesion properties in comparison with mature LN332. Whereas cell adhesion to the recombinant LG4/5 fragment relies solely on the heparan sulfate proteoglycan (HSPG) receptor syndecan‐1, we reveal that both syndecan‐1 and the alpha3beta1 integrin bind to precursor LN332. We further demonstrate that syndecan‐1 mediated cell adhesion to the LG4/5 fragment and pre‐LN332 allows the formation of fascin‐containing protrusions, depending on the GTPases Rac and Cdc42 activation. Reducing syndecan‐1 expression in normal keratinocytes prevents cell protrusions on pre‐LN332 with subsequent failure of the peripheral localization of the alpha3beta1 integrin. We finally show that cell migration on pre‐LN332 requires syndecan‐1. Therefore, the LG4/5 domain in precursor LN332 appears to trigger intracellular signaling events, which participate in keratinocyte motility. J. Cell. Physiol. 214:238–249, 2008. © 2007 Wiley‐Liss, Inc.