CAV1 siRNA Reduces Membrane Estrogen Receptor-α Levels and Attenuates Sexual Receptivity

Although classic estrogen receptors (ER) have been proposed to mediate estradiol signaling, it has been relatively recently that mechanisms of trafficking these receptors have been elucidated. ER alpha is palmitoylated and associates with caveolin proteins to be targeted to the cell membrane. Caveolins are scaffold proteins that not only traffic ER alpha to the membrane but also are involved in establishing metabotropic glutamate receptor interactions that are necessary for activating G protein signaling. To demonstrate the role of caveolin proteins in regulating an estradiol-dependent behavior, sexual receptivity, we used small interfering RNA to knock down caveolin-1 (CAV1) expression in the arcuate nucleus of the hypothalamus. In CAV1 knockdown rats, membrane, but not intracellular levels of ER alpha, were significantly reduced. As expected, estrogenic stimulation of the arcuate nucleus of the hypothalamus to medial preoptic nucleus projection was abrogated in CAV1 knockdown rats, indicating that the membrane-initiated activation of this circuit was compromised. Moreover, estradiol-induced lordosis behavior that is dependent on activation of mu-opioid receptors in the medial preoptic nucleus was also significantly reduced. Thus, CAV1-mediated ER alpha trafficking to the cell membrane is required for estradiol activation of circuits underlying female sexual receptivity. (Endocrinology 153: 3872-3877, 2012)