Involvement of misfolded CFTRΔF508 in endoplasmic reticulum (ER) stress in CF cell: Retention of CFTRΔF508 is associated with an increase of Ca
concentration in the lumen of ER and with the interaction with chaperone proteins. This induces activation of ERAD in order to degrade misfolded CFTRΔF508 by proteasome. In addition, increase of Grp78 induces activation of the UPR via the ATF-6. Whether ERAD and UPR are not sufficient to restore normal cellular parameters, EOR is activated resulting in apoptosis induction.