Adenomatous polyposis coli (APC) protein regulates epithelial cell migration and morphogenesis via PDZ domain-based interactions with plasma membranes.

The tumor suppressor adenomatous polyposis coli (APC) protein is localized at the plus ends of microtubules (MTs) at the migrating edges of cells. Here, we established Xenopus A6 epithelial cell transfectants expressing GFP-fused full-length APC (GFP-fAPC) or truncated APC lacking the COOH-terminal PDZ-binding motif TSV (GFP-APC(DeltaTSV)). Although both APC proteins were similarly accumulated at the MT ends, GFP-fAPC, but not GFP-APC(DeltaTSV), was associated with the basal and lateral plasma membranes and co-localized with a PDZ protein, DLG1. Stable over-expression of GFP-fAPC enforced cell-substrate attachment and thereby enhanced cell spreading on the substratum and induced polarized extension of lamellipodia and MTs during scratch-induced migration. Truncation of the PDZ-binding motif was sufficient to abolish these effects of GFP-fAPC. Furthermore, expression of GFP-APC(DeltaTSV) disturbed the establishment of a continuous epithelial monolayer. These results suggest that APC links MTs to plasma membranes through interactions with PDZ proteins, such that the migration and morphogenesis of epithelial cells can be properly regulated.