The endoplasmic reticulum (ER) stress response is triggered by the accumulation of unfolded proteins within the ER and is characterized by three events: the inhibition of translation (to prevent further protein accumulation), the up-regulated expression of polypeptide-folding proteins (known as the unfolded protein response or UPR) and the degradation of misfolded proteins by the ER-associated protein degradation (ERAD) system. Members of the homocysteine-inducible and ER stress-inducible ub