Abstract
Compromise in adherens junctions (AJs) is associated with several chronic inflammatory diseases. We reported previously that Janus kinase 3, a non-receptor tyrosine kinase, plays a crucial role in AJ formation through its interaction with β-catenin. In this report, we characterize the structural determinants responsible for Jak3 interactions with β-catenin and determine the functional implications of previously unknown tyrosine residues on β-catenin phosphorylated by Jak3. We demonstrate that Jak3 autophosphorylation was the rate-limiting step during Jak3 trans-phosphorylation of β-catenin, where Jak3 directly phosphorylated three tyrosine residues, viz. Tyr30, Tyr64, and Tyr86 in the N-terminal domain (NTD) of β-catenin. However, prior phosphorylation of β-catenin at Tyr654 was essential for further phosphorylation of β-catenin by Jak3. Interaction studies indicated that phosphorylated Jak3 bound to phosphorylated β-catenin with a dissociation constant of 0.28 μm, and although both the kinase and FERM (Band 41, ezrin, radixin, and moesin) domains of Jak3 interacted with β-catenin, the NTD domain of β-catenin facilitated its interactions with Jak3. Physiologically, Jak3-mediated phosphorylation of β-catenin suppressed EGF-mediated epithelial-mesenchymal transition and facilitated epithelial barrier functions by AJ localization of phosphorylated β-catenin through its interactions with α-catenin. Moreover, loss of Jak3-mediated phosphorylation sites in β-catenin abrogated its AJ localization and compromised epithelial barrier functions. Thus, we not only characterize Jak3 interaction with β-catenin but also demonstrate the mechanism of molecular interplay between AJ dynamics and EMT by Jak3-mediated NTD phosphorylation of β-catenin.
Keywords:
JAK; adherens junction; barrier functions; epithelial–mesenchymal transition (EMT); mucosal immunology; protein structure function; β-catenin.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Adherens Junctions / genetics
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Adherens Junctions / metabolism*
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Cell Line
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Epithelial-Mesenchymal Transition / physiology*
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Humans
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Janus Kinase 3 / genetics
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Janus Kinase 3 / metabolism*
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Phosphorylation / physiology
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Protein Domains
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Protein Transport / physiology
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Tyrosine / genetics
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Tyrosine / metabolism
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alpha Catenin / genetics
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alpha Catenin / metabolism
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beta Catenin / genetics
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beta Catenin / metabolism*
Substances
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alpha Catenin
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beta Catenin
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Tyrosine
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JAK3 protein, human
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Janus Kinase 3