19
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Rapid Uncoupling of Serotonin-1A Receptors in Rat Hippocampus by 17β-Estradiol in vitro Requires Protein Kinases A and C

      research-article

      Read this article at

      ScienceOpenPublisherPubMed
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          17β-Estradiol decreases R(+)8-OH-DPAT-stimulated [<sup>35</sup>S]GTPγS binding [an index of serotonin-1A (5-HT<sub>1A</sub>) receptor coupling] through the activation of estrogen receptors. We hypothesize that this occurs as a result of activation of protein kinase A (PKA) and/or protein kinase C (PKC) and phosphorylation of 5-HT<sub>1A</sub> receptors. Hippocampus from ovariectomized rats was incubated with 17β-estradiol in HEPES buffer (37°C). Cytosolic and membrane fractions were prepared to assess PKA and PKC activities, respectively. In separate experiments, membranes were prepared to measure R(+)8-OH-DPAT-stimulated [<sup>35</sup>S]GTPγS binding. 17β-Estradiol (50 n M) increased PKA and PKC activities approximately 2- to 3-fold. PKC activity was elevated at 10, 30 and 60 min, whereas PKA activity was increased at 10 and 30 min. The ability of 17β-estradiol to increase PKA and PKC was blocked by the estrogen receptor antagonist ICI 182,780 (1 µ M). A selective PKA inhibitor (KT 5720, 60 n M) blocked 17β-estradiol-stimulated PKA but not PKC activity. Conversely, the PKC inhibitor calphostin C (100 n M) blocked the increase in PKC activity produced by 17β-estradiol but not the PKA response. The protein kinase inhibitors individually blocked the effects of 17β-estradiol on R(+)8-OH-DPAT-stimulated [<sup>35</sup>S]GTPγS binding. By contrast, preincubation with the protein synthesis inhibitor cycloheximide (200 µ M) or the mitogen activated protein (MAP) kinase kinase inhibitor PD 98059 (50 µ M) was without effect. Incubation of hippocampus with 17β-estradiol (50 n M, 60 min) caused the phosphorylation of a protein consistent with the 5-HT<sub>1A</sub> receptor. These studies demonstrate that 17β-estradiol acts on estrogen receptors locally within the hippocampus through nongenomic mechanisms to activate PKA and PKC, phosphorylate 5-HT<sub>1A</sub> receptors and uncouple them from their G proteins.

          Related collections

          Most cited references13

          • Record: found
          • Abstract: not found
          • Article: not found

          Estrogen Actions in the Central Nervous System

          B S McEwen (1999)
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Immunocytochemical localization of serotonin1A receptors in the rat central nervous system.

            Specific anti-rat 5-hydroxytryptamine1A (serotonin1A) receptor antibodies raised in a rabbit injected with a synthetic peptide corresponding to a highly selective portion of the third intracellular loop of the receptor protein (El Mestikawy et al. [1990] Neurosci. Lett. 118:189-192) were used for immunohistochemical mapping of serotonin1A receptors in the brain and spinal cord of adult rats. The highest density of immunostaining was found in limbic areas (lateral septum, CA1 area of Ammon's horn and dentate gyrus in the hippocampus, and frontal and entorhinal cortices), in the anterior raphe nuclei, and in the interpeduncular nucleus, in agreement with previous autoradiographic studies with selective radioligands showing the enrichment of these regions in serotonin1A receptor binding sites. Serotonin1A receptor-like immunoreactivity was also present, but at a moderate level, in the neocortex, in some thalamic and hypothalamic nuclei, in the nucleus of the solitary tract, in the dorsal tegmentum, in the nucleus of the spinal tract of the trigeminal nerve, and in the superficial layers of the dorsal horn in the spinal cord. In contrast, extrapyramidal areas, including the caudate putamen, the globus pallidus, and the substantia nigra as well as the cerebellum, exhibited very low to no immunostaining by antiserotonin1A receptor antibodies. At the cellular level, both the plasma membrane of neuronal perikarya and fine neuronal processes probably corresponding to dendritic fields were found to bind antiserotonin1A receptor antibodies. Regional differences were noted regarding these two types of immunostaining, because only dendrites bound antibodies within the hippocampus and the lateral septum, whereas both dendrites and neuronal cell bodies were immunoreactive in the medial septum, in the diagonal band of Broca, and in the dorsal and median raphe nuclei. Therefore, differential addressing of serotonin1A receptors could occur from one neuron to another. In general, the distribution and density of serotonin1A receptor-like immunoreactivity in the whole brain and in spinal cord were consistent with the mapping of serotonin1A receptor binding sites and serotonin1A receptor mRNA previously established by immunoautoradiographic and in situ hybridization procedures.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Estrogens cause rapid activation of IP3-PKC-alpha signal transduction pathway in HEPG2 cells.

              The mechanisms through which steroids affect target cells are not fully understood. In addition to the classic model, there is now increasing evidence that steroids can exert rapid actions. It must still be elucidated if rapid and slow estrogen actions produce co-operative and/or integrative functions. The effects of estrogen on inositol trisphosphate (IP3) production and PKC-alpha levels on membrane in the HEPG2 cell line have been investigated. Results show that estrogen addition to HEPG2 cells causes a rapid increase of IP3 production. The effect was totally inhibited by pre-incubation with tyrosine-kinase inhibitor genisteine and with the anti-estrogen ICI 182,780. An increased PKC-alpha level on the membrane fraction was present 30 min after estrogen exposure. The strong signal could elicit a variety of cellular responses such as modulation of ion channel, stimulation of cell proliferation, and phosphorylation of cytosolic ER. The ability of estrogen to trigger IP3 production in human hepatoma cells is a novel aspect of estrogen action that requires the current model of hormone stimulation target cells to be revised. Copyright 1998 Academic Press.
                Bookmark

                Author and article information

                Journal
                NEN
                Neuroendocrinology
                10.1159/issn.0028-3835
                Neuroendocrinology
                S. Karger AG
                0028-3835
                1423-0194
                2002
                December 2002
                13 January 2003
                : 76
                : 6
                : 339-347
                Affiliations
                Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas School of Medicine, KansasCity,Kans., USA
                Article
                67583 Neuroendocrinology 2002;76:339–347
                10.1159/000067583
                12566941
                fcb22146-bd46-4fa7-870e-c4e9670c24bc
                © 2002 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.

                History
                : 17 February 2002
                : 06 June 2002
                Page count
                Figures: 5, References: 39, Pages: 9
                Categories
                Central Effects of Peripheral Hormones

                Endocrinology & Diabetes,Neurology,Nutrition & Dietetics,Sexual medicine,Internal medicine,Pharmacology & Pharmaceutical medicine
                Serotonin receptors,Gonadal steroids,Hippocampus,Serotonin agonists,Protein kinases,Serotonin

                Comments

                Comment on this article