Membrane estrogen receptors activate the metabotropic glutamate receptors mGluR5 and mGluR3 to bidirectionally regulate CREB phosphorylation in female rat striatal neurons.

Along with its ability to directly regulate gene expression, estradiol influences cell signaling and brain functions via rapid, membrane-initiated events. In the female rat striatum, estradiol activates membrane-localized estrogen receptors to influence synaptic neurotransmission, calcium channel activity, and behaviors related to motor control. Yet, the mechanism by which estradiol acts to rapidly affect striatal physiology has remained elusive. Here we find that membrane estrogen receptors (ERs) couple to the metabotropic glutamate receptors mGluR5 and mGluR3, providing the framework to understand how membrane estrogen receptors affect striatal function. Using CREB phosphorylation as a downstream measure of ER/mGluR activation, membrane-localized estrogen receptor α (ERα) activates mGluR5 signaling to mediate mitogen-activated protein kinase (MAPK)-dependent CREB phosphorylation. Further, ERα and estrogen receptor β (ERβ) activate mGluR3 to attenuate L-type calcium channel-dependent CREB signaling. Interestingly, while this fundamental mechanism of ER/mGluR signaling was initially characterized in hippocampal neurons, estrogen receptors in striatal neurons are paired with a different set of mGluRs, resulting in the potential to functionally isolate membrane-initiated estrogen signaling across brain regions via use of specific mGluR modulators. These results provide both a mechanism for the rapid actions of estrogens within the female striatum, as well as demonstrate that estrogen receptors can interact with a more diverse set of surface membrane receptors than previously recognized.