Hemidesmosomal collagen XVII enhances keratinocyte-collagen IV adhesion, and is involved in p38-MAPK-dependent cell migration and signaling

Collagen XVII (COL17), a transmembrane collagen, is thought to be involved in keratinocyte adhesion and possibly migration, as COL17 defects disrupt keratinocyte-basal lamina adhesion and underlie the disease non- Herlitz junctional epidermolysis bullosa (n-HJEB) (McGrath et al., Nat Genet 1995;11:83-6). COL17 is involved in keratinocyte adhesion and migration. Using siRNA to knockdown COL17 expression in HaCaT cells, we assessed cell characteristics including adhesion, migration and signaling. Control and siRNA transfected keratinocytes showed no difference in adhesion on plastic dishes after incubation for 8 hours in serum-free keratinocyte-growth medium, however when grown on collagen IV alone or BD matrigel (containing collagen IV and laminin isoforms) COL17 deficient cells showed significantly reduced adhesion compared to controls (P<0.01), and MEK1/2 and MAPK demonstrated reduced phosphorylation in COL17 depleted cells. Furthermore, COL17 deficient HaCaT cells plated on! plastic exhibited reduced motility that was p38MAP kinase dependent (after addition of the p38MAPK inhibitor SB203580). Conversely, keratinocyte adhesion was independent of p38MAPK signaling. Taken together, these results suggest COL17 has significantly wider signaling roles than were previously thought, including the involvement of COL17 in keratinocyte adhesion to collagen IV, in p38MAP kinase-dependent cell migration, and multiple cell signaling events pertaining to MEK1/2 phosphorylation. 33