Rap1 Regulates the Formation of E-Cadherin-Based Cell-Cell Contacts

Abstract

In epithelial tissues, cells are linked to their neighbors through specialized cell-cell adhesion proteins. E-cadherin is one of the most important membrane proteins for the establishment of intimate cell-cell contacts, but the molecular mechanism by which it is recruited to contact sites is largely unknown. We report here that the cytoplasmic domain of E-cadherin interacts with C3G, a guanine nucleotide exchange factor for Rap1. In epithelial cell cultures, ligation of the extracellular domain of E-cadherin enhances Rap1 activity, which in turn is necessary for the proper targeting of E-cadherin molecules to maturing cell-cell contacts. Furthermore, our data suggest that Cdc42 functions downstream of Rap1 in this process. We conclude that Rap1 plays a vital role in the establishment of E-cadherin-based cell-cell adhesion.

Rap1: a key regulator in cell-cell junction formation

“…In contrast to the observation in MCF7 cells that junction disassembly is not initiated by RapGAP expression, this causes junction disassembly, including loss of the tight junction protein ZO-1 in endothelial cells (Hogan et al, 2004;Wittchen et al, 2005). In spite of this, Rap1-induced regulation of E-cadherin and VEcadherin may not be a general mechanism for all classical cadherins since overexpression of RapGAP in HEK293 cells does not affect N-cadherin-mediated cell-cell junction formation (Hogan et al, 2004).…”

“…Furthermore, adhesion of ovarian carcinoma cells (OVCAR) to Fc-E-cadherin is inhibited by expression of dominant negative Rap1, which means that Rap1 regulates E-cadherin directly (Price et al, 2004). Importantly, Hogan et al found that the introduction of RapGAP into MCF7 cells does not disrupt mature E-cadherin-based cell-cell junctions but strongly reduces the reformation of adherens junctions upon re-addition of Ca 2+ (so-called Ca 2+ switch), which supports the idea that Rap1 has a role in junction maturation, not maintenance (Hogan et al, 2004). Remarkably, the tight junction marker ZO-1 is present at cell-cell contacts after Ca 2+ chelation.…”

“…Indeed, the RapGEF C3G interacts with E-cadherin and competes with ␤-catenin for binding to E-cadherin. The interaction is most prominent when cell-cell adhesion is induced after a Ca 2+ switch, and C3G disappears as the junctions mature (Hogan et al, 2004). C3G is also involved in nectin-induced activation of Rap1 (Fukuyama et al, 2005).…”

“…Rap1 might therefore only affect adherens junction regulation and not tight junctions directly. However, Hogan et al did not discuss whether the tight junctions were disrupted in any way under these experimental conditions (Hogan et al, 2004 …”

Gene Expression Profiling in TWIST‐Depleted Gastric Cancer Cells

“…RAP1A belongs to the family of Ras-like GTPases, whose function is in enhancing cell-matrix and cell-cell adhesion in an integrin-dependent manner, and enhancing cell-cell contact formation through E-cadherins (Hogan et al, 2004). Another integrin-dependent molecule, ILK (integrin-linked kinase), is a serine-threonine protein kinase that can interact directly with b-integrin.…”