Endoplasmic Reticulum Stress Alters The Localization Of The Prolyl Hydroxylase Ogfod1 In Adult Mouse Cardiomyocytes

Prolyl hydroxylation is a post-translational modification that is known to regulate several key cell functions including translation and protein stability. Enzymes that catalyze prolyl hydroxylation belong to the 2-oxoglutarate- and iron-dependent oxygenase (2OGDO) family. A newly-identified member of the 2OGDO enzyme family, 2-oxoglutarate- and iron-dependent oxygenase domain-containing protein 1 (Ogfod1), catalyzes prolyl hydroxylation of ribosomal protein s23 (Rps23), a component of the 40S ribosome. To establish an in vivo role for Ogfod1, we ablated Ogfod1 in mice and subjected isolated perfused hearts to ischemia and reperfusion and found Ogfod1 ablation to be cardioprotective. The mechanisms by which these changes occur are currently unknown, so we investigated Ogfod1 regulation and mechanisms of cardioprotection. Previous work has shown that Ogfod1-mediated Rps23 prolyl hydroxylation occurs in the nucleus, where ribosomes are assembled. Additionally, Ogfod1 localizes to cytoplasmic stress granules in transformed cells exposed to endoplasmic reticulum (ER) stress. Based on these studies, we tested the hypothesis that Ogfod1 localization, and subsequently its function, change in response to stress. We induced ER stress by treating isolated adult cardiomyocytes with thapsigargin, and monitored Ogfod1 localization using immunofluorescence. Thapsigargin inhibits sarco/endoplasmic reticulum Ca 2+ ATPase (SERCA) which activates the unfolded protein response. In the absence of thapsigargin, Ogfod1 localized to the nucleus, peri-nuclear space, cytoplasm, and cell membrane. After stress induction, Ogfod1 nuclear- and perinuclear-localization decreased. This suggests that in murine adult cardiomyocytes subjected to ER stress, Ogfod1 is exported from the nucleus, potentially as a mechanism for down-regulating its activity. As Ogfod1 ablation has been found to be cardioprotective in mice, understanding Ogfod1 localization and regulation in the cardiomyocyte stress response may provide mechanistic insight that will be useful in developing treatments for stressors such as heart failure.