Casein Kinase II Phosphorylation of E-cadherin Increases E-cadherin/β-Catenin Interaction and Strengthens Cell-Cell Adhesion

Heiko Lickert,Andreas Bauer,Rolf Kemler,Jörg Stappert

doi:10.1074/jbc.275.7.5090

Abstract

Beta-catenin, a member of the Armadillo repeat protein family, binds directly to the cytoplasmic domain of E-cadherin, linking it via alpha-catenin to the actin cytoskeleton. A 30-amino acid region within the cytoplasmic domain of E-cadherin, conserved among all classical cadherins, has been shown to be essential for beta-catenin binding. This region harbors several putative casein kinase II (CKII) and glycogen synthase kinase-3beta (GSK-3beta) phosphorylation sites and is highly phosphorylated. Here we report that in vitro this region is indeed phosphorylated by CKII and GSK-3beta, which results in an increased binding of beta-catenin to E-cadherin. Additionally, in mouse NIH3T3 fibroblasts expression of E-cadherin with mutations in putative CKII sites resulted in reduced cell-cell contacts. Thus, phosphorylation of the E-cadherin cytoplasmic domain by CKII and GSK-3beta appears to modulate the affinity between beta-catenin and E-cadherin, ultimately modifying the strength of cell-cell adhesion.

Highlights

E-cadherin belongs to the group of classical cadherins, Ca2ϩdependent adhesion molecules, that mediate cell-cell adhesion in many different tissues and various species [1]
In Vitro Phosphorylation of the Recombinant E-cadherin Cytoplasmic Domain by Casein Kinase II and GSK-3␤—Previously we had shown that a 30-aa region within the mouse E-cadherin cytoplasmic domain is necessary and sufficient for the interaction with ␤-catenin [21]
Consensus sequence analysis for various serine/threonine kinases indicated that Ser-840, -853, and -855 fit the classical consensus motif SXX(E/D) for casein kinase II (CKII), whereas Ser-849 basically fit the consensus motif SXXXS(P) for glycogen synthase kinase-3␤ (GSK-3␤) (Fig. 1A)

Summary

Introduction

E-cadherin belongs to the group of classical cadherins, Ca2ϩdependent adhesion molecules, that mediate cell-cell adhesion in many different tissues and various species [1]. E-cadherin is a type I transmembrane protein, making mostly homophilic cell-cell interactions via its extracellular domain, whereas the cytoplasmic domain is anchored to actin microfilaments via three cytoplasmic proteins ␣-, ␤-, and ␥-catenin (plakoglobin) [2, 3] Another catenin p120ctn is less tightly associated to E-cadherin, and its function is presently less well understood [4]. In a previous study we have shown that phosphorylation of E-cadherin is concentrated to a short stretch of 30 aa in the cytoplasmic domain [21] This region is necessary and sufficient for the interaction with ␤-catenin or plakoglobin, and it harbors a cluster of 8 Ser residues. We show that E-cadherin is phosphorylated in the Ser cluster by casein kinase II (CKII) and glycogen synthase kinase-3␤ (GSK-3␤) Preventing this phosphorylation reduces the interaction between ␤-catenin and E-cadherin in vitro and reduces E-cadherin-mediated cell-cell adhesion in transfected mouse NIH3T3 fibroblasts. Phosphorylation of E-cadherin appears to be a crucial mechanism by which cell-cell adhesion is modulated

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Results

Conclusion