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      P2X 7 Receptors Are Expressed during Mouse Nephrogenesis and in Collecting Duct Cysts of the cpk/cpk Mouse

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          Abstract

          Background: Purinergic receptors are cell-surface molecules that bind extracellular nucleotides, notably ATP. The P2X family includes seven nonselective ion channels with one member, P2X<sub>7</sub>, implicated in cytolytic pore formation and cell death. Materials and Methods: We sought P2X<sub>7</sub> expression in mouse nephrogenesis and cpk/cpk renal cyst growth, conditions in which both proliferation and apoptosis are prominent. Results: P2X<sub>7</sub> immunolocalized to condensed metanephric mesenchyme: both proliferation and apoptosis were detected in this compartment, assessed by proliferating cell nuclear antigen expression and propidium iodide-stained pyknotic nuclei respectively. Later in nephrogenesis, P2X<sub>7</sub> was detected in collecting ducts, a pattern persisting to maturity. A mesenchymal to epithelial shift of P2X<sub>7</sub> expression was also documented in ureter development. In cpk/cpk kidneys, P2X<sub>7</sub>-expressing collecting duct cysts dominated histology from two weeks until four weeks after birth, when animals die from uremia. In polycystic kidneys pyknotic nuclei were rarely identified in P2X<sub>7</sub>-expressing epithelia, but were detected between cysts, consistent with a non-apoptotic role for P2X<sub>7</sub> in cyst enlargement. Conclusion: P2X<sub>7</sub> is expressed during normal nephrogenesis and in a model of congenital polycystic kidney disease. Further experiments are necessary to define possible functions of P2X<sub>7</sub> in these settings.

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          Most cited references 11

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          Cyclin/PCNA is the auxiliary protein of DNA polymerase-delta.

          Identification of the cellular proteins whose expression is regulated during the cell cycle in normal cells is essential for understanding the mechanisms involved in the control of cell proliferation. A nuclear protein called cyclin of relative molecular mass 36,000 (Mr 36K), whose synthesis correlates with the proliferative state of the cell, has been identified in several cell types of human, mouse, hamster and avian origin. The rate of cyclin synthesis is very low in quiescent cells and increases several fold after serum stimulation shortly before DNA synthesis. Immunofluorescence and autoradiography studies have shown that the nuclear staining patterns of cyclin during S phase have a sequential order of appearance and a clear correlation can be found between DNA synthesis and cyclin positive nuclei. The proliferating cell nuclear antigen (PCNA) and cyclin have many common properties and it has been shown that these two are identical. Recently a protein which is required by DNA polymerase-delta for its catalytic activity with templates having low primer/template ratios has been isolated from calf thymus. We report here that cyclin and the auxiliary protein of DNA polymerase-delta are identical.
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            Pharmacology of cloned P2X receptors.

            There are seven P2X receptor cDNAs currently known. Six homomeric (P2X1, P2X2, P2X3, P2X4, P2X5, P2X7) and three heteromeric (P2X2/P2X3, P2X4/P2X6, P2X1/P2X5) P2X receptor channels have been characterized in heterologous expression systems. Homomeric P2X1 and P2X3 receptors are readily distinguishable by their rapid desensitization, the agonist action of alpha beta methyleneATP, and the block by 2',3'-O-(2,4,6-trinitrophenyl)-ATP. P2X2 receptors are unique among homomeric forms in their potentiation by low pH. Homomeric P2X4 receptors are much less sensitive to antagonism by suramin and pyridoxal 5-phosphate-6-azo-2',4'-disulfonic acid. Homomeric P2X7 receptors are the only form in which 2',3'-O-(4-benzoylbenzoyl)-ATP is more potent than ATP. The heteromeric P2X2/P2X3 receptor resembles P2X2 in slow desensitization kinetics and potentiation by low pH and is similar to P2X3 with respect to agonism by alpha beta methyleneATP and block by 2',3'-O-(2,4,6-trinitrophenyl)-ATP. Other agonists, antagonists, and ions that can be used to differentiate among the receptors are discussed.
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              Increased proliferation rate of lymphoid cells transfected with the P2X(7) ATP receptor.

              Human leukocytes can express the P2X(7) purinergic receptor, an ionic channel gated by extracellular ATP, for which the physiological role is only partially understood. Transfection of P2X(7) cDNA into lymphoid cells that lack this receptor sustains their proliferation in serum-free medium. Increased proliferation of serum-starved P2X(7) transfectants is abolished by the P2X(7) receptor blocker oxidized ATP or by the ATP hydrolase apyrase. Both wild type and P2X(7)-transfected lymphoid cells release large amounts of ATP into the culture medium. These data suggest the operation of an ATP-based autocrine/paracrine loop that supports lymphoid cell growth in the absence of serum-derived growth factors.
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                Author and article information

                Journal
                EXN
                Nephron Exp Nephrol
                10.1159/issn.1660-2129
                Cardiorenal Medicine
                S. Karger AG
                1660-2129
                2002
                2002
                09 January 2002
                : 10
                : 1
                : 34-42
                Affiliations
                aCentre for Nephrology, Institute of Urology and Nephrology, Middlesex Hospital, bNephro-Urology Unit, Institute of Child Health and cAutonomic Neuroscience Unit, Royal Free and University College Medical School, University College London, London, UK
                Article
                49896 Exp Nephrol 2002;10:34–42
                10.1159/000049896
                © 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.

                Page count
                Figures: 5, References: 41, Pages: 9
                Product
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/49896
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