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

      Estradiol and Testosterone Have Opposite Effects on Microtubule Polymerization

      ,

      Neuroendocrinology

      S. Karger AG

      Gonadal steroids, Cytoskeleton, Microtubules, Tubulin, Hippocampus

      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

          We have reported earlier the purification of tubulin from a plasmalemmal-microsomal fraction derived from rat hippocampus using an estradiol (E<sub>2</sub>) affinity column and the specific binding of tubulin to both E<sub>2</sub> and testosterone (T). To further investigate the effect of E<sub>2</sub> and T on the function of this protein, changes in microtubule polymerization as a result of exposure to the steroids were examined in this study, using both pure tubulin and rat hippocampal primary cell cultures. First, pure tubulin was incubated with or without steroids for 30 min on ice followed by polymerization at 37°C. The numbers of microtubules formed were counted from electron microscopic pictures. The results showed that at 30 min of polymerization, 10 n M, 30 n M and 30 µ M of E<sub>2</sub> inhibited microtubule assembly by –70%, –94%, and –92%, respectively (p < 0.01), while T at the same three concentrations stimulated it by +83%, +66%, and +121%, respectively (p < 0.05). The inhibitory effect of E<sub>2</sub> and the stimulatory effect of T were observed at 15, 30 and 60 min of the polymerization process. Next, primary cell cultures from 17-day rat fetus hippocampal tissues were treated with the steroids and polymerized microtubules (Triton X-100 resistant) were examined by immunocytochemistry. The results demonstrated that 60 min of E<sub>2</sub> treatment (10 n M) decreased the intensity of the immunolabeling of polymerized microtubules. The effect of T at n M concentration was not significant though it increased the immunolabeling at µ M concentration. Of great significance was a remarkable inhibition by T of the well-established depolymerization effect of colchicine in both the pure tubulin assay and the cell culture model, while E<sub>2</sub> was not effective. In an effort to pursue the possible mechanism(s) of the effect of E<sub>2</sub> and T on microtubule formation, we found that T only inhibited the microtubule depolymerization process without affecting the rate of polymerization. In contrast, E<sub>2</sub> modifies only the polymerization process without altering the depolymerization. Overall, these data indicate that E<sub>2</sub> and T may be considered as novel regulators of microtubule dynamics and thereby controlling cytoskeleton function in cells.

          Related collections

          Most cited references 11

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

          Stress and hippocampal plasticity.

           B McEwen (1998)
          The hippocampus is a target of stress hormones, and it is an especially plastic and vulnerable region of the brain. It also responds to gonadal, thyroid, and adrenal hormones, which modulate changes in synapse formation and dendritic structure and regulate dentate gyrus volume during development and in adult life. Two forms of structural plasticity are affected by stress: Repeated stress causes atrophy of dendrites in the CA3 region, and both acute and chronic stress suppresses neurogenesis of dentate gyrus granule neurons. Besides glucocorticoids, excitatory amino acids and N-methyl-D-aspartate (NMDA) receptors are involved in these two forms of plasticity as well as in neuronal death that is caused in pyramidal neurons by seizures and by ischemia. The two forms of hippocampal structural plasticity are relevant to the human hippocampus, which undergoes a selective atrophy in a number of disorders, accompanied by deficits in declarative episodic, spatial, and contextual memory performance. It is important, from a therapeutic standpoint, to distinguish between a permanent loss of cells and a reversible atrophy.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Structural insights into microtubule function.

             E Nogales (1999)
            Microtubules are polymers that are essential for, among other functions, cell transport and cell division in all eukaryotes. The regulation of the microtubule system includes transcription of different tubulin isotypes, folding of /¿-tubulin heterodimers, post-translation modification of tubulin, and nucleotide-based microtubule dynamics, as well as interaction with numerous microtubule-associated proteins that are themselves regulated. The result is the precise temporal and spatial pattern of microtubules that is observed throughout the cell cycle. The recent high-resolution analysis of the structure of tubulin and the microtubule has brought new insight to the study of microtubule function and regulation, as well as the mode of action of antimitotic drugs that disrupt normal microtubule behavior. The combination of structural, genetic, biochemical, and biophysical data should soon give us a fuller understanding of the exquisite details in the regulation of the microtubule cytoskeleton.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Structural interaction of cytoskeletal components

              Three-dimensional cytoskeletal organization of detergent-treated epithelial African green monkey kidney cells (BSC-1) and chick embryo fibroblasts was studied in whole-mount preparations visualized in a high voltage electron microscope. Stereo images are generated at both low and high magnification to reveal both overall cytoskeletal morphology and details of the structural continuity of different filament types. By the use of an improved extraction procedure in combination with heavy meromyosin subfragment 1 decoration of actin filaments, several new features of filament organization are revealed that suggest that the cytoskeleton is a highly interconnected structural unit. In addition to actin filaments, intermediate filaments, and microtubules, a new class of filaments of 2- to 3-nm diameter and 30- to 300-nm length that do not bind heavy merymyosin is demonstrated. They form end-to-side contacts with other cytoskeletal filaments, thereby acting as linkers between various fibers, both like (e.g., actin- actin) and unlike (e.g., actin-intermediate filament, intermediate filament-microtubule). Their nature is unknown. In addition to 2- to 3-nm filaments, actin filaments are demonstrated to form end-to-side contacts with other filaments. Y-shaped actin filament “branches” are observed both in the cell periphery close to ruffles and in more central cell areas also populated by abundant intermediate filaments and microtubules. Arrowhead complexes formed by subfragment 1 decoration of actin filaments point towards the contact site. Actin filaments also form end-to-side contacts with microtubules and intermediate filaments. Careful inspection of numerous actin-microtubule contacts shows that microtubules frequently change their course at sites of contact. A variety of experimentally induced modifications of the frequency of actin-microtubule contacts can be shown to influence the course of microtubules. We conclude that bends in microtubules are imposed by structural interactions with other cytoskeletal elements. A structural and biochemical comparison of whole cells and cytoskeletons demonstrates that the former show a more inticate three-dimensional network and a more complex biochemical composition than the latter. An analysis of the time course of detergent extraction strongly suggests that the cytoskeleton forms a structural backbone with which a large number of proteins of the cytoplasmic ground substance associate in an ordered fashion to form the characteristic image of the “microtrabecular network” (J.J. Wolosewick and K.R. Porter. 1979. J. Cell Biol. 82: 114-139).
                Bookmark

                Author and article information

                Journal
                NEN
                Neuroendocrinology
                10.1159/issn.0028-3835
                Neuroendocrinology
                S. Karger AG
                0028-3835
                1423-0194
                2003
                April 2003
                21 May 2003
                : 77
                : 4
                : 258-272
                Affiliations
                Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Ill., USA
                Article
                70281 Neuroendocrinology 2003;77:258–272
                10.1159/000070281
                12766326
                © 2003 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: 10, References: 51, Pages: 15
                Categories
                Sex Steroids and Reproductive Neuroendocrinology

                Comments

                Comment on this article