Extra-nuclear estrogen receptor GPR30 regulates serotonin function in rat hypothalamus.

Selective serotonin reuptake inhibitors (SSRIs), such as Prozac, are used to treat mood disorders. SSRIs attenuate (i.e. desensitize) serotonin 1A (5-HT(1A)) receptor signaling, as demonstrated in rats through decreased release of oxytocin and adrenocorticotropin hormone (ACTH) following 5-HT(1A) receptor stimulation. Maximal therapeutic effects of SSRIs for treatment of mood disorders, as well as effects on hypothalamic 5-HT(1A) receptor signaling in animals, take 1 to 2 weeks to develop. Estradiol also attenuates 5-HT(1A) receptor signaling, but, in rats, these effects occur within 2 days; thus, estrogens or selective estrogen receptor modulators may serve as useful short-term tools to accelerate desensitization of 5-HT(1A) receptors in response to SSRIs if candidate estrogen receptor targets in the hypothalamus are identified. We found high levels of GPR30, which has been identified recently as a pertussis-toxin (PTX) sensitive G-protein-coupled estrogen receptor, in the hypothalamic paraventricular nucleus (PVN) of rats. Double-label immunohistochemistry revealed that GPR30 co-localizes with 5-HT(1A) receptors, corticotrophin releasing factor (CRF) and oxytocin in neurons in the PVN. Pretreatment with PTX to the PVN before peripheral injections of 17-beta-estradiol 3-benzoate completely prevented the reduction of the oxytocin response to the 5-HT(1A) receptor agonist, (+)-8-hydroxy-2-dipropylaminotetralin (DPAT). Treatment with the selective GRP30 agonist, G-1, attenuated 5-HT(1A) receptor signaling in the PVN as measured by an attenuated oxytocin (by 29%) and ACTH (by 31%) response to DPAT. This study indicates that a putative extra-nuclear estrogen receptor, GPR30, may play a role in estradiol-mediated attenuation of 5-HT(1A) receptor signaling, and potentially in accelerating the effects of SSRIs in treatment of mood disorders.

Molecular cloning of a human melanoma-associated chondroitin sulfate proteoglycan.

A human melanoma-associated chondroitin sulfate proteoglycan (MCSP), recognized by mAb 9.2.27, plays a role in stabilizing cell-substratum interactions during early events of melanoma cell spreading on endothelial basement membranes. We report here the molecular cloning and nucleotide sequencing of cDNA encoding the entire core protein of human MCSP and provide its deduced amino acid sequence. This core protein contains an open reading frame of 2322 aa, encompassing a large extracellular domain, a hydrophobic transmembrane region, and a relatively short cytoplasmic tail. Northern blot analysis indicated that MCSP cDNA probes detect a single 8.0-kb RNA species expressed in human melanoma cell lines. In situ hybridization experiments with a segment of the MCSP coding sequence localized MCSP mRNA in biopsies prepared from melanoma skin metastases. Multiple human Northern blots with an MCSP-specific probe revealed a strong hybridization signal only with melanoma cells and not with other human cancer cells or a variety of human fetal and adult tissues. These data indicate that MCSP represents an integral membrane chondroitin sulfate proteoglycan expressed by human malignant melanoma cells. The availability of cDNAs encoding MCSP should facilitate studies designed to establish correlations between structure and function of this molecule and help to establish its role in the progression of human malignant melanoma.