Cross‐talk between Connexin 43 and CFTR in ER quality control (949.4)

Abstract

An endoplasmic reticulum (ER) resident chaperone, ERp29, was previously identified to promote the quality control of cystic fibrosis transmembrane conductance regulator protein (CFTR). ERp29 also regulates the trafficking and oligomerization of a gap junction protein, connexin43 (Cx43). The ERp29/Cx43 complex regulates Cx43 oligomerization in the ER allowing for the formation hexameric hemichannels only in the TGN. Here we examined the ability of HeLa cells stably expressing Cx43 to form Cx43 membrane channels in the presence of the wild type and the most common mutant form of CFTR, ΔF508, in order to assess chaperone cross‐talk. CFTR expression is controlled by a TetOn system where CFTR mRNA and protein expression is regulated to mRNA and protein levels observed in primary airway cells. With a TetOn expression system we are able to probe cellular stress conditions in the presence and absence of transiently expressed CFTR. We assessed ER stress by using a luciferase‐based transcription factor assay, qRT‐PCR for ER stress markers and chaperones, and we also analyzed the effect of Δ508‐CFTR on gap junction intracellular communication via dye transfer studies. Mutant ΔF508‐CFTR can induce trafficking errors through ERp29 leading to decreased Cx43 protein trafficking and increased overall cellular sensitization to ER stress in a HeLa cell model which mimics cystic fibrosis airway cell protein expression levels.Grant Funding Source: Supported by: Emory+Children's CCFADR, Emory URC, CFF, NIH‐NIAAA, NIH‐NHLBI