A novel mechanism in wound healing: Laminin 332 drives MMP9/14 activity by recruiting syndecan-1 and CD44.

• Re -epithelialization is a critical step in the skin wound healing response. • Keratinocytes deposit extracellular matrix laminin 332 along their path while migrating. • Matrix metalloproteinases-9 and −14 exert their proteolytic activity in epithelial podosomes in primary keratinocytes. • The laminin α3 chain globular domains 4 and 5 recruit and merge syndecan-1 and CD44 in podosomes. • The proteoglycan receptor syndecan-1 regulates epithelial podosome formation and proteolytic activity. Re -epithelialization describes the resurfacing of a skin wound with new epithelium. In response to various stimuli including that of growth factors, cytokines and extracellular matrix (ECM), wound edge epidermal keratinocytes undergo cytoskeleton rearrangements compatible with their motile behavior and develop protrusive adhesion contacts. Matrix metalloproteinases (MMP) expression is crucial for proper cell movement and ECM remodeling; however, their deposition mechanism is unknown in keratinocytes. Here, we show that similar to cytokine IL-1ß, the precursor laminin 332 pro-migratory fragment G45 induces expression of the MMP-9 pro-enzyme, which together with MMP-14, further exerts its proteolytic activity within epithelial podosomes. This event strictly depends on the expression of the proteoglycan receptor syndecan-1 that was found in a ring surrounding the podosome core, co-localised with CD44. Our findings uncover that by directly recruiting both syndecan-1 and CD44, the laminin-332 G45 domain plays a major role in regulating mechanisms underlying keratinocyte / ECM remodeling during wound repair. [ABSTRACT FROM AUTHOR]