Involvement of G Protein-Coupled Receptor 30 (GPR30) in Rapid Action of Estrogen in Primate LHRH Neurons

Abstract

Previously, we have reported that 17β-estradiol (E₂) induces an increase in firing activity of primate LH-releasing hormone (LHRH) neurons. The present study investigates whether E₂ alters LHRH release as well as the pattern of intracellular calcium ([Ca²⁺]_i) oscillations and whether G protein-coupled receptor 30 (GPR30) plays a role in mediating the rapid E₂ action in primate LHRH neurons. Results are summarized: 1) E₂, the nuclear membrane-impermeable estrogen, estrogen-dendrimer conjugate, and the plasma membrane-impermeable estrogen, E₂-BSA conjugate, all stimulated LHRH release within 10 min of exposure; 2) whereas the estrogen receptor antagonist, ICI 182,780, did not block the E₂-induced LHRH release, E₂ application to cells treated with pertussis toxin failed to induce LHRH release; 3) GPR30 mRNA was expressed in olfactory placode cultures, and GPR30 protein was expressed in a subset of LHRH neurons; 4) pertussis toxin treatment blocked the E₂-induced increase in [Ca²⁺]_i oscillations; 5) knockdown of GPR30 in primate LHRH neurons by transfection with small interfering RNA (siRNA) for GPR30 completely abrogated the E₂-induced changes in [Ca²⁺]_i oscillations, whereas transfection with control siRNA did not; 6) the estrogen-dendrimer conjugate-induced increase in [Ca²⁺]_i oscillations also did not occur in LHRH neurons transfected with GPR30 siRNA; and 7) G1, a GPR30 agonist, resulted in changes in [Ca²⁺]_i oscillations, similar to those observed with E₂. Collectively, E₂ induces a rapid excitatory effect on primate LHRH neurons, and this rapid action of E₂ appears to be mediated, in part, through GPR30.