GPR30-mediated estrogenic regulation of actin polymerization and spatial memory involves SRC-1 and PI3K-mTORC2 in the hippocampus of female mice

Aims: The G-protein-coupled Estrogen Receptor GPR30 (also referred to as GPER) has been implicated in the estrogenic regulation of hippocampal plasticity and spatial memory; however, the molecular mechanisms are largely unclear.

Methods: In this study, we initially examined the levels of GPR30 in the hippocampus of postnatal, ovariectomy (OVX)- and letrozole (LET)-treated female mice. Under G1, G15, and/or OVX treatment, the spatial memory, spine density, levels of ERα, ERβ, and SRC-1, selected synaptic proteins, mTORC2 signals (Rictor and p-AKT Ser473), and actin polymerization dynamics were subsequently evaluated. Furthermore, G1, G15, and/or E2 combined with SRC-1 and/or PI3K inhibitors, actin Cytoskeleton polymerization modulator JPK, and CytoD treatments were used to address the mechanisms that underlie GPR30 regulation in vitro. Finally, mTORC2 Activator A-443654 (A4) was used to explore the role of mTORC2 in GPR30 regulation of spatial memory.

Results: The results showed that high levels of GPR30 were detected in the adult hippocampus and the levels were downregulated by OVX and LET. OVX induced an impairment of spatial memory, and changes in Other parameters previously described were reversed by G1 and mimicked by G15. Furthermore, the E2 effects on SRC-1 and mTORC2 signals, synaptic proteins, and actin polymerization were inhibited by G15, whereas G1 effects on these parameters were inhibited by the blockade of SRC-1 or PI3K; the levels of synaptic proteins were regulated by JPK and CytoD. Importantly, G15-induced actin depolymerization and spatial memory impairment were rescued by mTORC2 activation with A4.

Conclusions: Taking together, these results demonstrated that decreased GPR30 induces actin depolymerization through SRC-1 and PI3K/mTORC2 pathways and ultimately impairs learning and memory, indicating its potential role as a therapeutic target against hippocampus-based, E2-related memory impairments.