Phosphorylation of TRPC4 as a regulatory mechanism of Isoc

Abstract

Calcium signaling mediates a number of cellular events, and in many non‐excitable cells, store‐operated calcium entry (SOCE) represents the major Ca2+ event for signaling. In SOCE, depletion of ER Ca2+ stores leads to extracellular Ca2+ entry through SOC channels. Pulmonary artery endothelial cells (PAECs) exhibit a Ca2+‐selective SOCE current termed Isoc. Activation of Isoc in PAECs leads to formation of inter‐endothelial cell gaps. TRPC proteins 1 and 4 contribute to Isoc channel architecture. The region encompassing the protein 4.1 binding site and adjacent proline‐rich region on the TRPC4 subunit are essential for Isoc channel activation. Isoc inactivation is phosphorylation‐ and Ca2+‐dependent but the identity of kinases/phosphatases and their targets are still being explored. TRPC4 is a promising target for phosphoregulation of Isoc. Here, we examine the phosphorylation status of TRPC4 following activation of thapsigargin‐induced SOCE in PAECs. Following store depletion, TRPC4 phosphorylation increases as evidenced by western blot. In the presence of a calcineurin phosphatase inhibitor, baseline and thapsigargin‐induced TRPC4 phosphorylation is increased, and thapsigargin‐induced inter‐endothelial gap formation is reduced. These data suggest TRPC4 phosphorylation plays a role in Isoc regulation. Supported by 1F32HL112565–01 and 5R00HL089361