Contact-dependent promotion of cell migration by the OL-protocadherin-Nap1 interaction

OL-protocadherin (OL-pc) is a transmembrane protein belonging to the cadherin superfamily, which has been shown to accumulate at cell-cell contacts via its homophilic interaction, but its molecular roles remain elusive. In this study, we show that OL-pc bound Nck-associated protein 1 (Nap1), a protein that regulates WAVE-mediated actin assembly. In astrocytoma U251 cells not expressing OL-pc, Nap1 was localized only along the lamellipodia. However, exogenous expression of OL-pc in these cells recruited Nap1 as well as WAVE1 to cell-cell contact sites. Although OL-pc expression had no effect on the motility of solitary U251 cells, it accelerated their movement when they were in contact with one another, causing concomitant reorganization of F-actin and N-cadherin at cell junctions. OL-pc mutants lacking the Nap1-binding site exhibited no such effect. N-cadherin knockdown mimicked OL-pc expression in enhancing cell movement. These results suggest that OL-pc remodels the motility and adhesion machinery at cell junctions by recruiting the Nap1-WAVE1 complex to these sites and, in turn, promotes the migration of cells.