The roles of membrane estrogen receptor subtypes in modulating dopamine transporters in PC‐12 cells

Abstract

The effects of 17β‐estradiol (E2) on dopamine (DA) transport could explain gender and life‐stage differences in the incidence of some neurological disorders. We tested the effects of E2 at physiological concentrations on DA efflux in nerve growth factor‐differentiated rat pheochromocytoma cells that express estrogen receptors (ER) α, ERβ, and G‐protein coupled receptor 30 (GPR30), and DA transporter (DAT). DAT efflux was determined as the transporter‐specific loss of 3H‐DA from pre‐loaded cells; a 9–15 min 10−9 M E2 treatment caused maximal DA efflux. Such rapid estrogenic action suggests a non‐genomic response, and an E2‐dendrimer conjugate (limited to non‐nuclear actions) caused DA efflux within 5 min. Efflux dose–responses for E2 were non‐monotonic, also characteristic of non‐genomic estrogenic actions. ERα siRNA knockdown abolished E2‐mediated DA efflux, while ERβ knockdown did not, and GPR30 knockdown increased E2‐mediated DA efflux (suggesting GPR30 is inhibitory). Use of ER‐selective agonists/antagonists demonstrated that ERα is the predominant mediator of E2‐mediated DA efflux, with inhibitory contributions from GPR30 and ERβ. E2 also caused trafficking of ERα to the plasma membrane, trafficking of ERβ away from the plasma membrane, and unchanged membrane GPR30 levels. Therefore, ERα is largely responsible for non‐genomic estrogenic effects on DAT activity.

The possible role of estrogen and selective estrogen receptor modulators in a rat model of Parkinson's disease

“…Therefore, ERα is largely responsible for non-genomic estrogenic effects on dopamine transporter activity (Alyea et al, 2008). Other findings suggest that, although both ER subtypes play a role in the maintenance of cell number in the SN, ERα may play a more significant role (Johnson et al, 2010).…”

“…These may include its antioxidant effects as well as enhancement of cerebral blood flow (Zhao and Brinton, 2007). These nongenomic effects probably occur via both plasma membrane receptors and non-receptor-mediated pathways (Alyea et al, 2008). Some actions, such as modulation of neurotransmitters, may occur by both genomic and nongenomic mechanisms (Taber et al, 2001).…”

G protein-coupled receptor 30 in tumor development

“…GPR30 expression in tumor tissues and cell lines GPR30 gene expression has been detected in at least four kinds of human tumor specimens or cell lines (Table 2), including breast cancer [20,26,28,30,34,47,[56][57][58], endometrial cancer [29,45,49,59], ovarian cancer [21,60,61], thyroid cancer [46], and a rat pheochromocytoma cell line PC-12 [62]. In human breast cancer, GPR30 expression is decreased on both mRNA [56] and protein levels [30] compared with that in normal tissues, and its expression level is positively correlated with ERa [56].…”

International Union of Basic and Clinical Pharmacology. XCVII. G Protein–Coupled Estrogen Receptor and Its Pharmacologic Modulators

“…As a result of their charge and size (Generation 6 PAMAM contains 256 primary amines and has a molecular mass of ;58 kDa), such E2-dendrimer conjugates (E2DCs) remain outside the nucleus, and in fact the cell (i.e., cytoplasm), with reported cytoplasmic localization in punctate structures likely the result of receptor-mediated endocytosis or pinocytosis. E2DCs have been shown to mediate multiple nonnuclear/rapid signaling events such as ERK1/2, Src, and eNOS activation through both ERs (Alyea et al, 2008;Chambliss et al, 2010) and GPER ) but not nuclear events such as transcription of endogenous E2 target genes or MCF7 cell proliferation because E2DCs are 10,000-fold less potent than E2 in genomic actions (Harrington et al, 2006;Chambliss et al, 2010). Although the function of E2DCs through ERa is well established, it is unclear how the E2 moiety of E2DCs (or E2-BSA) gains access to nonnuclear ERa located either in the cytosol or at the inner face of the plasma membrane.…”