Dynasore modulates store-operated calcium entry and mitochondrial calcium release in corneal epithelial cells.

Dysregulation of calcium homeostasis can precipitate a cascade of pathological events that lead to tissue damage and cell death. Dynasore is a small molecule that inhibits endocytosis by targeting classic dynamins. In a previous study, we showed that dynasore can protect human corneal epithelial cells from damage due to tert-butyl hydroperoxide (tBHP) exposure by restoring cellular calcium (Ca) homeostasis. Here we report results of a follow-up study aimed at identifying the source of the damaging Ca. Store-operated Ca entry (SOCE) is a cellular mechanism to restore intracellular calcium stores from the extracellular milieu. We found that dynasore effectively blocks SOCE in cells treated with thapsigargin (TG), a small molecule that inhibits pumping of Ca into the endoplasmic reticulum (ER). Unlike dynasore however, SOCE inhibitor YM-58483 did not interfere with the cytosolic Ca overload caused by tBHP exposure. We also found that dynasore effectively blocks Ca release from internal sources. The inefficacy of inhibitors of ER Ca channels suggested that this compartment was not the source of the Ca surge caused by tBHP exposure. However, using a Ca-measuring organelle-entrapped protein indicator (CEPIA) reporter targeted to mitochondria, we found that dynasore can block mitochondrial Ca release due to tBHP exposure. Our results suggest that dynasore exerts multiple effects on cellular Ca homeostasis, with inhibition of mitochondrial Ca release playing a key role in protection of corneal epithelial cells against oxidative stress due to tBHP exposure.