The protein phosphatase 2 A regulatory subunit P pp2r2a is required for C onnexin‐43 dephosphorlyation during epidermal barrier acquisition

Epidermal barrier acquisition during late mammalian development is a prerequisite for terrestrial existence. Over a 24‐h period, the epidermis goes from being a barrier‐deficient, dye permeable epithelium to a barrier‐competent epithelium. We have previously shown that A kt signalling is necessary for barrier acquisition in the mouse and that the protein phosphatase 2 A regulatory subunit P pp2r2a causes barrier acquisition by dephosphorylation of cJ un. Here, we demonstrate that there is transient interaction between the gap junction protein C onnexin 43 ( C x43) and Z onula occludins‐1 ( Z o‐1) during epidermal barrier acquisition. Ppp2r2a knockdown prevented plasma membrane co‐localisation and interaction between the two proteins. Ppp2r2a knockdown also increased phosphorylation at S erine 368 of C onnexin 43. Cx43 phosphorlyation at S erine368 occurred just prior to the interaction between C onnexin 43 and Z o‐1. We therefore propose a model in which P pp2r2a is required both for the initial interaction between Z o‐1 and C x43 and the consequent dephosphorylation of C onnexin 43, preventing interaction of Z o‐1 and allowing Z o‐1 to initiate tight junction formation and barrier acquisition.