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      Calcium Flux in Neuroblastoma Cells Is a Coupling Mechanism between Non-Genomic and Genomic Modes of Estrogens

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          Abstract

          Estrogens have been demonstrated to rapidly modulate calcium levels in a variety of cell types. However, the significance of estrogen-mediated calcium flux in neuronal cells is largely unknown. The relative importance of intra- and extracellular sources of calcium in estrogenic effects on neurons is also not well understood. Previously, we have demonstrated that membrane-limited estrogens, such as E-BSA given before an administration of a 2-hour pulse of 17β-estradiol (E<sub>2</sub>), can potentiate the transcription mediated by E<sub>2</sub> from a consensus estrogen response element (ERE)-driven reporter gene. Inhibitors to signal transduction cascades given along with E-BSA or E<sub>2</sub> demonstrated that calcium flux is important for E-BSA-mediated potentiation of transcription in a transiently transfected neuroblastoma cell line. In this report, we have used inhibitors to different voltage-gated calcium channels (VGCCs) and to intracellular store receptors along with E-BSA in the first pulse or with E<sub>2</sub> in the second pulse to investigate the relative importance of these channels to estrogen-mediated transcription. Neither L- nor P-type VGCCs seem to play a role in estrogen action in these cells; while N-type VGCCs are important in both the non-genomic and genomic modes of estrogen action. Specific inhibitors also showed that the ryanodine receptor and the inositol trisphosphate receptor are important to E-BSA-mediated transcriptional potentiation. This report provides evidence that while intracellular stores of calcium are required to couple non-genomic actions of estrogen initiated at the membrane to transcription in the nucleus, extracellular sources of calcium are also important in both non-genomic and genomic actions of estrogens.

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          Most cited references 50

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          The steroid and thyroid hormone receptor superfamily.

           Ronald Evans (1988)
          Analyses of steroid receptors are important for understanding molecular details of transcriptional control, as well as providing insight as to how an individual transacting factor contributes to cell identity and function. These studies have led to the identification of a superfamily of regulatory proteins that include receptors for thyroid hormone and the vertebrate morphogen retinoic acid. Although animals employ complex and often distinct ways to control their physiology and development, the discovery of receptor-related molecules in a wide range of species suggests that mechanisms underlying morphogenesis and homeostasis may be more ubiquitous than previously expected.
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            Functional domains of the human estrogen receptor.

            Two domains of the human estrogen receptor, responsible for hormone binding (region E) and tight nuclear binding (region C), are essential for the receptor to activate efficiently the transcription of estrogen-responsive genes. Region D, which joins the DNA- and hormone-binding domains, can be altered without affecting activation. Deletion of the N-terminal domain (region A/B) has no effect on activation of a reporter gene containing a vitellogenin estrogen-responsive element (ERE) and the HSV-tk promoter, whereas it severely impairs activation of the human pS2 gene promoter. Deletion of most or all of the hormone-binding domain leads to only about 5% constitutive transcriptional activity, yet these mutants appear to bind efficiently to an ERE in vivo. Apparently, region C recognizes the ERE of target genes, and the hormone-binding domain plays an essential role for efficient activation of transcription.
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              Inositol 1,4,5-trisphosphate receptors as signal integrators.

              The inositol 1,4,5 trisphosphate (IP3) receptor (IP3R) is a Ca2+ release channel that responds to the second messenger IP3. Exquisite modulation of intracellular Ca2+ release via IP3Rs is achieved by the ability of IP3R to integrate signals from numerous small molecules and proteins including nucleotides, kinases, and phosphatases, as well as nonenzyme proteins. Because the ion conduction pore composes only approximately 5% of the IP3R, the great bulk of this large protein contains recognition sites for these substances. Through these regulatory mechanisms, IP3R modulates diverse cellular functions, which include, but are not limited to, contraction/excitation, secretion, gene expression, and cellular growth. We review the unique properties of the IP3R that facilitate cell-type and stimulus-dependent control of function, with special emphasis on protein-binding partners.
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                Author and article information

                Journal
                NEN
                Neuroendocrinology
                10.1159/issn.0028-3835
                Neuroendocrinology
                S. Karger AG
                0028-3835
                1423-0194
                2005
                July 2005
                29 July 2005
                : 81
                : 3
                : 174-182
                Affiliations
                Departments of aBiology and bChemistry, Pennsylvania State University, University Park, Pa. and cLaboratory of Neurobiology and Behavior, The Rockefeller University, New York, N.Y., USA
                Article
                87000 Neuroendocrinology 2005;81:174–182
                10.1159/000087000
                16020926
                © 2005 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 5, References: 73, Pages: 9
                Categories
                Original Paper

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