The ubiquitin-proteasome pathway inhibitor TAK-243 has major effects on calcium handling in mammalian cells

Abstract

The ubiquitin-proteasome pathway (UPP) is a major route for protein degradation and a key regulatory mechanism in mammalian cells. UPP inhibitors, including TAK-243, a first-in-class inhibitor of the E1 ubiquitin-activating enzyme, are currently being used and tested for treatment of a range of diseases, particularly cancer. Here, we reveal that TAK-243 has major effects on Ca²⁺ handling in a range of cultured mammalian cells (αT3, HeLa and SH-SY5Y). Effects were seen on agonist-induced Ca²⁺ mobilization, basal cytosolic Ca²⁺ levels, Ca²⁺ leak from the endoplasmic reticulum (ER), store-operated Ca²⁺ entry and mitochondrial Ca²⁺ uptake. These effects correlated with induction of ER stress, as measured by PERK activation / eIF2α phosphorylation, and most seemed to be underpinned by enhanced Ca²⁺ leak from the ER. Overall, these data indicate that TAK-243 reprograms the Ca²⁺-handling properties of mammalian cells and that these effects should be considered when UPP inhibitors are employed as therapeutic agents.

Keywords: Calcium; Endoplasmic reticulum; Inositol 1,4,5-trisphosphate receptor; Intracellular signaling; TAK-243; cancer.