ATF4 and age-related macular degeneration: In human RPE cells, inhibition of XBP1 intensifies CSE-induced apoptosis; in contrast, suppression of the PERK/ATF4/CHOP pathway improves RPE cell survival, suggesting that the XBP1 pathway and the PERK/ATF4/CHOP pathway play differential roles in RPE survival during AMD [74].