Multifaceted regulation of Ca2+ efflux via the plasma membrane Ca2+‐ATPase by 17β‐estradiol in the vascular endothelium

Abstract

Many of the beneficial effects of estrogen in the vasculature involve Ca2+‐dependent activities. Ca2+ efflux via the plasma membrane Ca2+‐ATPase (PMCA) represents a major component of the Ca2+ signaling machinery in cells. We observed in vascular endothelial cells that chronic treatment with 17β‐estradiol dose‐dependently decreases PMCA activity without affecting PMCA expression levels. Treatment with 17β‐estradiol promotes tyrosine phosphorylation at both the 135‐kDa (PMCA) and 60‐kDa levels on PMCA immunoprecipitate. We identified this 60‐kDa protein to be a glycosylated form of the novel G protein‐coupled estrogen receptor 1 (GPER). Inhibition of Src kinase activity suppresses estrogen‐induced tyrosine phosphorylation on PMCA and GPER. Functionally, Src inhibition not only restores PMCA activity in cells treated with 17β‐estradiol, but increases it by 50%. Consistent with the 50% increase in PMCA activity upon Src inhibition in estrogen‐treated cells, the interaction between PMCA and calmodulin is increased by 50%, an effect that occurs independently of Src kinase activity. These results indicate that estrogen inhibits PMCA activity by promoting Src‐dependent tyrosine phosphorylation and interaction with GPER, effects that mask the stimulatory effect of enhanced CaM binding.