Specific Phosphorylation of p120-Catenin Regulatory Domain Differently Modulates Its Binding to RhoA

Abstract

p120-catenin is an adherens junction-associated protein that controls E-cadherin function and stability. p120-catenin also binds intracellular proteins, such as the small GTPase RhoA. In this paper, we identify the p120-catenin N-terminal regulatory domain as the docking site for RhoA. Moreover, we demonstrate that the binding of RhoA to p120-catenin is tightly controlled by the Src family-dependent phosphorylation of p120-catenin on tyrosine residues. The phosphorylation induced by Src and Fyn tyrosine kinases on p120-catenin induces opposite effects on RhoA binding. Fyn, by phosphorylating a residue located in the regulatory domain of p120-catenin (Tyr112), inhibits the interaction of this protein with RhoA. By contrast, the phosphorylation of Tyr217 and Tyr228 by Src promotes a better affinity of p120-catenin towards RhoA. In agreement with these biochemical data, results obtained in cell lines support the important role of these phosphorylation sites in the regulation of RhoA activity by p120-catenin. Taken together, these observations uncover a new regulatory mechanism acting on p120-catenin that contributes to the fine-tuned regulation of the RhoA pathways during specific signaling events.E-cadherin function is controlled posttranslationally by a family of proteins, named catenins, that bind to its cytosolic tail. Two members of this family, p120-catenin and ␤-catenin, interact at different sites of the E-cadherin molecule and are engaged in distinct functions. Whereas ␤-catenin is required for recruiting the actin cytoskeleton, p120-catenin is necessary for the stabilization of E-cadherin at the cell membrane (3). As a consequence, E-cadherin is rapidly internalized and degraded in the absence of p120-catenin (7, 13). Consequently, p120-catenin ablation in vivo causes E-cadherin deficiency, leading to severe defects in adhesion, cell polarity, and epithelial morphogenesis (7).Besides this role in regulating E-cadherin stability, p120-catenin interacts with other proteins involved in the modulation of cell-to-cell contacts. For instance, p120-catenin associates with Fer and Fyn tyrosine kinases (16,27,36). These kinases specifically phosphorylate ␤-catenin in Tyr142 (27), a modification that promotes release of ␤-catenin from the adherens junctional complex and transport to the nucleus (2, 27). Moreover, p120-catenin can interact with the Yes tyrosine kinase (27) and with a number of phosphotyrosine (PTyr) phosphatases, such as PTP (39), DEP1 (12), and SHP-1 (14, 21). These multiple associations suggest a role for p120-catenin as a scaffold protein for enzymes regulating events such as the stability of the adherens junctional complex (29).p120-catenin modulates the activity of other cellular factors. Similarly to ␤-catenin, it can be detected in the nucleus (34), where it interacts with the transcriptional factor Kaiso (6). Studies performed with Xenopus laevis have demonstrated that association of p120-catenin relieves the repression caused by Kaiso on Wnt signaling (17,25).Several results indicate that p...

Cdc42 GTPase and Rac1 GTPase act downstream of p120 catenin and require GTP exchange during gastrulation of zebrafish mesoderm

“…Exons for human and zebrafish p120 catenin d1 found in the UCSC genome database are similar but not identical. Six tyrosine and four serine and threonine residues that are phosphorylated in humans are conserved in zebrafish; two tyrosine and four serine threonine residues are absent from the zebrafish sequence, suggesting that they may not be essential residues (human: tyr-96, -112, thr-310, and ser-122, 312, -873), although tyr-112 is implicated in RhoA GTPase binding (Castaño et al, 2007).…”

p120 and Kaiso RegulateHelicobacter pylori-induced Expression of Matrix Metalloproteinase-7

“…Previous studies have suggested that phosphorylation of a number of tyrosine residues within the p120 regulatory domain may play a role in p120 signaling (Mariner et al, 2004;Shibata et al, 2004;Castano et al, 2007;Reynolds, 2007). Therefore, we investigated whether H. pylori infection similarly altered levels of p120 tyrosine phosphorylation.…”

The regulatory or phosphorylation domain of p120 catenin controls E-cadherin dynamics at the plasma membrane

“…Phosphorylation of p120 has been extensively mapped, and it has been shown that the majority of the phosphorylated tyrosines, serines and threonines are in a 100 amino acid region in the amino terminus, termed the p120 regulatory domain that is important for signal integration from non-receptor kinases [14,16,38]. Threonine 310 is within the regulatory domain, while threonine 916 is in the carboxyl terminus outside of the regulatory domain.…”

“…On the other hand, Ozawa and Ohkubo found that tyrosine phosphorylation of p120 in v-Src transfected Ecadherin-expressing L cells led to reduced cell-cell adhesion without influencing the affinity of p120 for E-cadherin [11]. In addition to its role in regulating E-cadherin function, p120 also functions as a Rho guanine nucleotide dissociation inhibitor, or Rho GDI [12,13], and Castano et al recently showed that this function of p120 is regulated by Fyn/Src-dependent tyrosine phosphorylation [14].…”