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Despite in depth characterization of the role of IRE1 alpha (inositol-requiring enzyme 1 alpha) in activating the unfolded protein response (UPR) in the ER - little is known about the molecular mechanisms by which this ER protein has shown to regulate intracellular calcium levels and subsequent apoptosis. Intracellular calcium homeostasis is fundamental to many physiological processes, and an increase in Ca2+ is associated with both the early and late stages of apoptosis.

p53 is a tumor suppressor that has a central role in regulating cell cycle arrest, DNA repair, and apoptosis. p53 is widely studied for its role in cancer and is mutated or altered in more than half of all cancers (1). This widespread role in tumorigenesis has made p53 one of the most highly studied proteins and a target for anti-cancer therapeutics. Normally, p53 allows cells to sense and respond to cellular stress such as DNA damage or hypoxia (2). In response to these signals, p53 is activated through post-translational modification and protein stabilization.

Dynamin-related Protein 1 (DRP1) is known to function in mitochondrial and peroxisomal division and mediate membrane fission through oligomerization into ring-like structure and sever the mitochondrial membrane, through a GTP hydrolysis-dependent mechanism.