Janus kinase 3 regulates adherens junctions and epithelial mesenchymal transition through β-catenin

J Biol Chem. 2017 Oct 6;292(40):16406-16419. doi: 10.1074/jbc.M117.811802. Epub 2017 Aug 17.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adherens Junctions / genetics
  • Adherens Junctions / metabolism*
  • Cell Line
  • Epithelial-Mesenchymal Transition / physiology*
  • Humans
  • Janus Kinase 3 / genetics
  • Janus Kinase 3 / metabolism*
  • Phosphorylation / physiology
  • Protein Domains
  • Protein Transport / physiology
  • Tyrosine / genetics
  • Tyrosine / metabolism
  • alpha Catenin / genetics
  • alpha Catenin / metabolism
  • beta Catenin / genetics
  • beta Catenin / metabolism*

Substances

  • alpha Catenin
  • beta Catenin
  • Tyrosine
  • JAK3 protein, human
  • Janus Kinase 3

Associated data

  • PDB/2Z6G