Role of cell adhesion-associated protein, pinin (DRS/memA), in corneal epithelial migration

PURPOSE. To determine whether the cellular distribution of cell adhesion-as sociated protein, pinin, is altered during corneal epithelial migration in response to debridement wounding and to determine the effect of overexpress ion of pinin in cultured epithelial cells. METHODS. Corneas from guinea pig and embryonic (day 17) chickens were excis ed, wounded, and placed on organ-culture rafts. At time points from 0 to 24 hours, corneas were cryosectioned and subsequently analyzed by immunofluor escence or immunoelectron microscopy for the presence and distribution of p inin. Cultured epithelial cell line MDCK (Madin Darby canine kidney) conflu ent monolayers were wounded by scraping and examined by immunofluorescence for pinin and desmoplakin. MDCK cells were transfected with full-length pin in cDNA. After selection in Geneticin, clones of pinin-transfected cells we re isolated. Monolayers of transfected cells were scrape wounded and assaye d for their ability to migrate. RESULTS. Within 2 hours after wounding, although morphologically identifiab le desmosomes were present on migrating epithelial cells, the association o f pinin to desmosomes was greatly reduced. Finally, after completion of wou nd closure, pinin returned to the corneal epithelial desmosome. Wounding of confluent epithelial monolayers (MDCK) in vitro demonstrated a very simila r change in the distribution of pinin, whereas desmoplakin remained cell bo undary-associated. Transfection of pinin into cultured epithelial cells res ulted in an overexpression of pinin. Clones of cells expressing high levels of pinin exhibited marked reduction in their ability to migrate after woun ding. CONCLUSIONS. Pinin is involved in corneal epithelium migration. The localiz ation of pinin at or near the desmosome is correlated with the epithelial q uiescence. The loss of pinin from the cell boundary correlates with the tra nsition from quiescence to actively migrating. Overexpressing pinin in cult ured epithelial cells affects epithelial homeostasis and, in turn, drives t he epithelial cells to a hyperstable epithelial adhesive state and inhibits the transition from quiescence to migratory.