O‐GlcNAcylation of STIM1 in pulmonary artery endothelial cells (1176.8)

Extracellular calcium entry following endoplasmic reticulum store depletion, known as store‐operated calcium entry (SOCE), represents the major Ca 2+ signaling event in non‐excitable cells. In the pulmonary endothelium, SOCE through the Ca 2+ ‐selective I soc leads to increased permeability via inter‐endothelial cell gap formation. I soc activity may be regulated through post‐translational modification, and indeed, inactivation is phosphorylation‐dependent. Regulation may occur via modification of proteins comprising the channel pore or of accessory proteins such as stromal interacting molecule 1 (STIM1). We showed calcineurin regulates SOCE in pulmonary artery endothelial cells (PAECs) via dephosphorylation of STIM1. In addition to phosphorylation, STIM1 may be regulated by O‐linked β‐N‐acetylglucosamine (O‐GlcNAc), which can have an inverse relationship with phosphorylation on the same residues. Here, we sought to determine whether O‐GlcNAcylation regulates SOC entry in PAECs, and whether this modification has a relationship to phosphorylation. When PAECs were treated with Thaimet G, an inhibitor of O‐GlcNAcylation, SOCE increased. Western blots for O‐GlcNAc showed multiple proteins in PAECs are O‐GlcNAcylated, including a major band at ~85 kDa, likely STIM1. This band decreases upon thapsigargin treatment as phosphorylation increases. These data suggest that O‐GlcNAcylation plays a role and has an inverse relationship with phosphorylation in the regulation of SOCE. Grant Funding Source : Supported by 1F32HL112565‐01, R00HL089361 and R01HL107778