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      α 2-Macroglobulin: A Binding Protein for Transforming Growth Factor-β and Various Cytokines

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          Abstract

          α<sub>2</sub>-Macroglobulin (α<sub>2</sub>M) is a large plasma glycoprotein that has long been known as an irreversible inhibitor of a variety of proteinases. More recently, it has been reported that numerous growth factors, cytokines and hormones bind to α<sub>2</sub>M through diverse mechanisms. We review here a series of observations from our laboratory that support the concept that α<sub>2</sub>M is a carrier protein for transforming growth factor-β (TGF-β) and allows this factor to act as an autocrine regulator of adrenocortical steroidogenic functions. α<sub>2</sub>M was found to be synthesized and secreted by primary cultures of bovine adrenocortical cells in fairly large amounts (1 μg/l0<sup>6</sup> cells/24 h). TGF-β is also secreted by this cell type, although under a latent form. Two distinct latent TGF-β complexes have been characterized in adrenocortical cell conditioned medium, one of which is a complex between α<sub>2</sub>M and TGF-β. Although α<sub>2</sub>M prevents the binding of TGF-β to its membrane receptors, long-term incubation of α<sub>2</sub>M with adrenocortical cells results in inhibition of cortisol production similar to that observed in the presence of TGF-β alone. Taken together, these observations suggest that adrenocortical cells can release active TGF-β from its latent complex with α<sub>2</sub>M through an unknown mechanism. α<sub>2</sub>M can therefore be considered as a TGF-β carrier protein.

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          Author and article information

          Journal
          HRE
          Horm Res Paediatr
          10.1159/issn.1663-2818
          Hormone Research in Paediatrics
          S. Karger AG
          978-3-8055-6290-4
          978-3-318-00047-4
          1663-2818
          1663-2826
          1996
          1996
          09 December 2008
          : 45
          : 3-5
          : 227-232
          Affiliations
          CEA, Biochimie des Régulations Cellulaires Endocrine, INSERM Unité 244, Département de Biologie Moléculaire et Structurale, CEN.G, Grenoble, France
          Article
          184793 Horm Res 1996;45:227–232
          10.1159/000184793
          8964589
          © 1996 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
          Pages: 6
          Categories
          Hormone Binding Proteins: Physiology and Clinical Implications

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