Phosphorylation potential of Drosophila E-Cadherin intracellular domain is essential for development and regulating adherens junction biosynthetic dynamics [RESEARCH REPORT]

Yi-Jiun Chen, Juan Huang, Lynn Huang, Erin Austin, and Yang Hong

E-Cadherin intracellular domain contains a highly conserved serine cluster whose phosphorylations are essential for binding to β-Catenin in vitro. In cultured cells phosphorylations of specific serine residues within the cluster are also required for regulating adherens junction (AJ) stability and dynamics. However, much less is known how such phosphorylations of E-Cadherin regulate the AJ formation and dynamics in vivo. In this report we generated an extensive array of Drosophila E-Cadherin (DE-Cad) endogenous knock-in alleles that carry mutations targeting this highly conserved serine cluster. Our mutant analyses suggest that the overall phosphorylation potential, other than the potential site-specific phosphorylations, of serine cluster enhance the recruitment of β-Catenin by DE-Cad in vivo. Moreover, phosphorylation potential of the serine cluster only moderately increases β-Catenin in AJ and is in fact dispensable for AJ formation in vivo. Nonetheless, phosphorylation-dependent recruitment of β-Catenin is essential for development, likely by enhancing the interactions between DE-Cad and α-Catenin. Specific phospho-mutants also dramatically affect the biosynthetic turn-over of mutant DE-Cad during apical-basal polarization and specifically rescued the polarity defects in embryonic epithelia lacking polarity proteins Stardust and Crumbs.

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