Article

Integrin α3β1–dependent β-catenin phosphorylation links epithelial Smad signaling to cell contacts

Pulmonary and Critical Care Division, Department of Medicine, and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94143, USA.
The Journal of Cell Biology (Impact Factor: 9.69). 02/2009; 184(2):309-22. DOI: 10.1083/jcb.200806067
Source: PubMed

ABSTRACT Injury-initiated epithelial to mesenchymal transition (EMT) depends on contextual signals from the extracellular matrix, suggesting a role for integrin signaling. Primary epithelial cells deficient in their prominent laminin receptor, alpha3beta1, were found to have a markedly blunted EMT response to TGF-beta1. A mechanism for this defect was explored in alpha3-null cells reconstituted with wild-type (wt) alpha3 or point mutants unable to engage laminin 5 (G163A) or epithelial cadherin (E-cadherin; H245A). After TGF-beta1 stimulation, wt epithelial cells but not cells expressing the H245A mutant internalize complexes of E-cadherin and TGF-beta1 receptors, generate phospho-Smad2 (p-Smad2)-pY654-beta-catenin complexes, and up-regulate mesenchymal target genes. Although Smad2 phosphorylation is normal, p-Smad2-pY654-beta-catenin complexes do not form in the absence of alpha3 or when alpha3beta1 is mainly engaged on laminin 5 or E-cadherin in adherens junctions, leading to attenuated EMT. These findings demonstrate that alpha3beta1 coordinates cross talk between beta-catenin and Smad signaling pathways as a function of extracellular contact cues and thereby regulates responses to TGF-beta1 activation.

0 Followers
 · 
183 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The arrival of multicellularity in evolution facilitated cell-cell signaling in conjunction with adhesion. As the ectodomains of cadherins interact with each other directly in trans (as well as in cis), spanning the plasma membrane and associating with multiple other entities, cadherins enable the transduction of "outside-in" or "inside-out" signals. We focus this review on signals that originate from the larger family of cadherins that are inwardly directed to the nucleus, and thus have roles in gene control or nuclear structure-function. The nature of cadherin complexes varies considerably depending on the type of cadherin and its context, and we will address some of these variables for classical cadherins versus other family members. Substantial but still fragmentary progress has been made in understanding the signaling mediators used by varied cadherin complexes to coordinate the state of cell-cell adhesion with gene expression. Evidence that cadherin intracellular binding partners also localize to the nucleus is a major point of interest. In some models, catenins show reduced binding to cadherin cytoplasmic tails favoring their engagement in gene control. When bound, cadherins may serve as stoichiometric competitors of nuclear signals. Cadherins also directly or indirectly affect numerous signaling pathways (e.g., Wnt, receptor tyrosine kinase, Hippo, NFκB, and JAK/STAT), enabling cell-cell contacts to touch upon multiple biological outcomes in embryonic development and tissue homeostasis. © 2015 Elsevier Inc. All rights reserved.
    Current Topics in Developmental Biology 01/2015; 112:129-96. DOI:10.1016/bs.ctdb.2014.11.018 · 4.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Transforming growth factor (TGF)-β triggers the epithelial-to-mesenchymal transition (EMT) of cancer cells via well-orchestrated crosstalk between Smad and non-Smad signaling pathways, including Wnt/β-catenin. Since EMT-induced motility and invasion play a critical role in cancer metastasis, EMT-related molecules are emerging as novel targets of anti-cancer therapies. Traf2- and Nck-interacting kinase (TNIK) has recently been considered as a first-in-class anti-cancer target molecule to regulate Wnt signaling pathway, but pharmacologic inhibition of its EMT activity has not yet been studied. Here, using 5-(4-methylbenzamido)-2-(phenylamino)thiazole-4-carboxamide (KY-05009) with TNIK-inhibitory activity, its efficacy to inhibit EMT in cancer cells was validated. The molecular docking/binding study revealed the binding of KY-05009 in the hinge region of TNIK, and the inhibitory activity of KY-05009 against TNIK was confirmed by an ATP competition assay (Ki, 100 nM). In A549 cells, KY-05009 significantly and strongly inhibited the TGF-β-activated EMT through the attenuation of Smad and non-Smad signaling pathways, including the Wnt, NF-κB, FAK-Src-paxillin-related focal adhesion, and MAP kinases (ERK and JNK) signaling pathways. Continuing efforts to identify and validate potential therapeutic targets associated with EMT, such as TNIK, provide new and improved therapies for treating and/or preventing EMT-based disorders, such as cancer metastasis and fibrosis.
    PLoS ONE 10/2014; 9(10):e110180. DOI:10.1371/journal.pone.0110180 · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: During secondary palate development, palatal shelves adhere to each other in the midline to form a midline epithelial seam leading to palatal closure. Cell-cell and cell-extracellular matrix adhesions, which are mediated by cell adhesion receptors, E-cadherin and integrins, are implicated in the process of adhesion of the palatal shelves. Src family kinases (SFK) function downstream of both receptors. In this study, we focused on the role of SFK in the process of palatal adhesion. During palatal adhesion, the expression of SFK mRNA, as well as localization and quantitation of the protein in the activated form, were examined by real-time qPCR and immunofluorescence. Palatal organ cultures were performed to identify the effect of pharmacological inhibition of SFK on palatal adhesion. Activated SFKs were found to be co-localized with adhesion receptors, E-cadherin and integrins in the palatal medial edge epithelium. Src, Fyn and Yes subfamily members were expressed in the palatal tissue. The expression of SFK mRNA and the quantity of the activated form of the protein were upregulated during palatal adhesion. An SFK inhibitor, PP2, blocked palatal adhesion, but another SFK inhibitor, SU6656 was not inhibitory. However, the combination of SU6656 and either of the p38MAPK inhibitors, SB203580 or BIRB0796, showed similar inhibitory effects on palatal adhesion compared to PP2 alone. The p38MAPK inhibitors alone did not alter palatal adhesion. Real-time qPCR revealed that p38MAPK alpha and delta were elevated during palatal adhesion. This study indicates that palatal cell adhesion is dependent on signaling from integrin receptors and E-cadherin through SFK and p38MAPK.
    The International Journal of Developmental Biology 01/2014; 58(5):335-41. DOI:10.1387/ijdb.130289yk · 2.57 Impact Factor