Enterophilin-1 Interacts with Focal Adhesion Kinase and Decreases β1 Integrins in Intestinal Caco-2 Cells

Abstract

Intestinal cell growth and differentiation are tightly regulated by growth factors and extracellular matrix components along the crypt-villus axis. We previously described enterophilin-1 (Ent-1) as a new intestinal protein associated with growth arrest and enterocyte differentiation. Ent-1 interacted with sorting nexin 1 and decreased cell surface epidermal growth factor receptor. Because β1 integrins are mostly found in vivo in the proliferative crypt cells, we investigated the role of Ent-1 in the fate of β1 integrin subunits. In undifferentiated intestinal Caco-2 cells, overexpression of Ent-1 induces a marked decrease of α 5β1, integrin pools, whereas α 2β1, integrin is weakly affected. Conversely, overexpression of sorting nexin 1 has no effect on integrin levels despite its ability to interact with Ent-1. Interestingly, we identified focal adhesion kinase as a new Ent-1 partner using yeast two-hybrid screening and co-precipitation experiments. Furthermore by confocal microscopy, we observed that Ent-1 and β1 integrins partly co-localize on vesicular structures, suggesting a role for Ent-1 in integrin trafficking. Because focal adhesion kinase is able to bind both Ent-1 and β1 integrins, the asa kinase might act as a molecular bridge between the two proteins. Altogether, these results support a role of Ent-1 in regulating β 1, integrin expression that could favor intestinal differentiation.