DDIT3 and familial dilated cardiomyopathy: Considering the potential involvement of ER stress in DCM among Bag5 point mutant KI mice, we further examined the ER stress signaling pathway and the participation of glucose-regulated protein (GRP78) and C/EBP Homologous Protein (CHOP) in response to TN, both of which are implicated in the unfolded protein response (UPR) and ER stress-induced apoptosis.