[26] Previous studies have demonstrated that PDI is involved in a wide range of physiological and disease processes. [27] Toldo and colleagues identified PDI as a cardioprotective factor in cardiomyocyte ischemia due to its ability to relieve ER stress and prevent accumulation of unfolded proteins. [28] Beside its function within the ER, PDI also has been demonstrated to catalyzes the isomerization of disulfide bonds of cell surface proteins. [29], [30], [31], [32] The interaction changes the protein conformation of cell surface proteins resulting in the alternation of their functions. The gene discussed is P4HB; the disease is ischemia.