Regulation of the Assembly and Adhesion Activity of E-cadherin by Nectin and Afadin for the Formation of Adherens Junctions in Madin-Darby Canine Kidney Cells

Abstract

The Ca 2؉ -independent immunoglobulin-like molecule nectin first forms cell-cell adhesion and then assembles cadherin at nectinbased cell-cell adhesion sites, resulting in the formation of adherens junctions (AJs). Afadin is a nectin-and actin filament-binding protein that connects nectin to the actin cytoskeleton. Here, we studied the roles and modes of action of nectin and afadin in the formation of AJs in cultured MDCK cells. The trans-interaction of nectin assembled E-cadherin, which associated with p120 ctn , ␤-catenin, and ␣-catenin, at the nectin-based cell-cell adhesion sites in an afadin-independent manner. However, the assembled E-cadherin showed weak cell-cell adhesion activity and might be the non-transinteracting form. This assembly was mediated by the IQGAP1-dependent actin cytoskeleton, which was organized by Cdc42 and Rac small G proteins that were activated by the action of trans-interacting nectin through c-Src and Rap1 small G protein in an afadinindependent manner. However, Rap1 bound to afadin, and this Rap1-afadin complex then interacted with p120 ctn associated with non-trans-interacting E-cadherin, thereby causing the trans-interaction of E-cadherin. Thus, nectin regulates the assembly and cellcell adhesion activity of E-cadherin through afadin, nectin signaling, and p120 ctn for the formation of AJs in Madin-Darby canine kidney cells.

Rap1: a key regulator in cell-cell junction formation

“…Also, extracellular stimuli, including those that stimulate production of cAMP which activates Epac, induce Rap1 activation. The role of Rap1 in junction formation proposed to be constitutively active, but not by full-length p120-catenin (Sato et al, 2006). These results point to a model in which nectins activate Rap1, which then binds to and activates afadin/AF6.…”

“…4). As a Rap1 effector and a regulator of p120-catenin, afadin/AF6 is a good candidate for mediating Rap1-dependent effects on E-cadherin (Boettner et al, 2000;Davis et al, 2003;Sato et al, 2006). In addition, Rap1 plays an important role in the regulation of the cytoskeleton by activating Rac and Cdc42 through the binding and recruitment of the GEFs Tiam1 and Vav2 (Arthur et al, 2004).…”

Anchoring Junctions As Drug Targets: Role in Contraceptive Development

“…1), and establishment of nectin-based adherens junctions required annexin II and IQGAP in MDCK cells (Katata et al, 2003;Yamada et al, 2005aYamada et al, , 2006a. Furthermore, nectin-afadin can also recruit tight junction proteins such as claudin, occludin, JAM-A, and ZO-1 to the junctional complex (Yokoyama et al, 2001;Fukuhara et al, 2002;Takai and Nakanishi, 2003;Sato et al, 2006), suggesting the existence of cross talk between different junction types. In addition, nectin-1 and nectin-3 have been shown to bind directly to Par-3 , a cell polarity protein, but Par-3 was not required for nectin-based cell adhesion (Ooshio et al, 2007).…”

“…Recruitment of cadherins has been shown to be mediated by nectin-induced activation of Rac, Cdc42 and Rap1 through c-Src, leading to reorganization of the actin cytoskeleton Ogita and Takai, 2006). After sequestration of cadherins at the adherens junction, nectins continue to regulate cadherin function by (i) inhibiting the endocytosis of cadherin and (ii) affecting the conformation of cadherin extracellular domains to facilitate trans-interactions (Hoshino et al, 2005;Sato et al, 2006). Nectins also regulate cytoskeletal dynamics via F-actin binding proteins that interact directly with nectin [e.g., afadin, ␣-catenin, ␣-actinin, vinculin, annexin II and IQGAP Miyoshi and Takai, 2007)] (Fig.…”

Role of Scaffold Protein Afadin Dilute Domain-interacting Protein (ADIP) in Platelet-derived Growth Factor-induced Cell Movement by Activating Rac Protein through Vav2 Protein

“…In addition to integrin ␣v␤3, the cell-cell adhesion molecule occludin and the scaffold proteins IQGAP and vinculin have been reported to regulate both cell movement and cell-cell junctions (40 -44). Our previous and present data also demonstrate that afadin and ADIP are involved in cell movement and cell-cell junctions (13,19,45). For the physiological regulation of mesenchymal-epithelial transition and epithelial-mesenchymal transition, it may be advantageous that some molecules mutually function in cell movement and cell-cell junctions.…”