Activation of Endoplasmic Reticulum-Specific Stress Responses Associated with the Conformational Disease Z α1-Antitrypsin Deficiency

Conformational diseases are a class of disorders associated with aberrant protein accumulation in tissues and cellular compartments. Z alpha1-antitrypsin (A1AT) deficiency is a genetic disease associated with accumulation of misfolded A1AT in the endoplasmic reticulum (ER) of hepatocytes. We sought to identify intracellular events involved in the molecular pathogenesis of Z A1AT-induced liver disease using an in vitro model system of Z A1AT ER accumulation. We investigated ER stress signals induced by Z A1AT and demonstrated that both the ER overload response and the unfolded protein response were activated by mutant Z A1AT, but not wild-type M A1AT. Interestingly, activation of the unfolded protein response pathway required an additional insult, whereas NF-kappa B activation, a hallmark of the ER overload response, was constitutive. These findings have important implications for the design of future therapeutics for Z A1AT liver disease and may also impact on drug design for other conformational diseases.