Rationale Regulator of G-protein signaling 4 (RGS4) is a brain-enriched negative modulator of G-protein-coupled receptor signaling. Decreased availability of RGS4 in the frontal cortex and striatum has been described in animal models of schizophrenia and drug addiction. However, cellular and behavioral consequences of dysregulated RGS4-dependent receptor signaling in the brain remain poorly understood. Objective To investigate whether RGS4, through inhibiting function of mGluR5 receptors in the dorsal striatum (dSTR), regulates cellular and behavioral responses to acute amphetamine. Methods After HSV-RGS4 was infused into dSTR, RGS4 overexpression as well as binding of recombinant RGS4 to mGluR5 were assessed. The effect of RGS4 overexpression on behavioral activity induced by the intra-striatal mGluR5 agonist, DHPG, or amphetamine was recorded. Activation of extracellular signal-regulated kinase (ERK) and Akt (protein kinase B) was measured in the dSTR tissue at the end of each behavioral experiment. Results RGS4 overexpressed in the dSTR co-immunoprecipitated with mGluR5 receptors and suppressed both behavioral activity, as well as phospho-ERK levels induced by DHPG. RGS4 over-expression or the mGluR5 antagonist, MTEP attenuated amphetamine-induced phospho-ERK (but not phospho-Akt) levels. RGS4 suppressed amphetamine–induced vertical activity and augmented horizontal activity over 90 min. Similarly, MTEP augmented amphetamine-induced horizontal activity but did not affect vertical activity. Conclusions The present data demonstrate that RGS4 in the dSTR attenuates amphetamine-induced ERK signaling and decreases the behavioral efficacy of acute amphetamine likely by limiting mGluR5 function.
ETS proteins represent one of the largest families of transcription factors with diverse functions that activate or repress the expression of genes that are involved in various biological processes, including cellular proliferation, differentiation, development, transformation and apoptosis. The ETS family gene, PDEF (prostate derived ets factor), is expressed in normal epithelial tissues including prostate, breast, colon and bladder. Significantly, PDEF protein is present in non-invasive cancers but reduced or absent in most invasive cancers. By re-expression and knock-down of PDEF in cancer cell lines, we and others have shown that PDEF target genes control aspects of the metastatic process, including cell growth, migration and invasion. We hypothesize that PDEF is important for normal developmental processes and that loss of PDEF regulatory networks is a key event in the development of invasive cancer. To study the function of Pdef in vivo, we generated mice with constitutive Pdef knockout (Pdef −/−). Specific stages of mammary development were examined, including early-pubescent (5 week), virgin adult (8 week), pregnancy (days 7.5 and 13.5), lactation (days 1 and 7) and involution (day 7). Inhibition of the development of the ductal tree and an increase in ductal side branching and terminal end bud proliferation was observed in 5-8 week old virgin Pdef −/− mice. TGFβ1 and ERα are required for development of the ductal tree during puberty and mRNA levels for both are reduced in the Pdef −/− mice at 5 and 8 weeks of age. Incomplete lobuloalveoli development was observed in Pdef −/− pregnant and lactating mice, although no phenotypic effects were observed in the resultant pups. To explore the role of Pdef in mammary tumor progression and metastasis, we generated mice expressing the MMTV-PyMT or MMTV-Neu oncogene in wild type and Pdef −/− backgrounds. No impact of Pdef dosage upon tumor incidence or growth was observed in the PyMT model; however, initial tumor formation was delayed by 4 weeks (8.9 vs. 4.8) and time from tumor initiation to sacrifice was 3 weeks longer (29.4 vs 26.4) in the Pdef −/− Neu model. Significantly, an increase in lung metastasis was observed in the Pdef −/− mice in both the PyMT and Neu models. Thus, loss of Pdef in vivo is associated with defects in mammary development and increased metastasis in mouse models of breast cancer, suggesting Pdef is a metastasis suppressor. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3397.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.