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J. Biol. Chem., Vol. 279, Issue 18, 19257-19263, April 30, 2004

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Functional Coupling of Rat Myometrial 1-Adrenergic Receptors to Gh/Tissue Transglutaminase 2 during Pregnancy^*

Morgan Dupuis, Arlette Lévy, and Sakina Mhaouty-Kodja

From the Laboratoire de Physiologie et Physiopathologie, Unité Mixte de Recherche-CNRS 7079, Paris CEDEX 05, France

Gh protein, which exhibits both transglutaminase and GTPase activities, represents a new class of GTP-binding proteins. In the present study, we characterized Gh in rat uterine smooth muscle (myometrium) and followed its expression during pregnancy by reverse transcription-PCR and Western blot. We also measured transglutaminase and GTP binding functions and used a smooth muscle cell line to evaluate the role of Gh in cell proliferation. The results show that pregnancy is associated with an up-regulation of Gh expression at both the mRNA and protein level. Gh induced during pregnancy is preferentially localized to the plasma membrane. This was found associated with an increased ability of plasma membrane preparations to catalyze Ca²⁺-dependent incorporation of [³H]putrescine into casein in vitro. In the cytosol, significant changes in the level of immunodetected Gh and transglutaminase activity were seen only at term. Activation of 1-adrenergic receptors (1-AR) enhanced photoaffinity labeling of plasma membrane Gh. Moreover, the level of 1-AR-coupled Gh increased progressively with pregnancy, which parallels the active period of myometrial cell proliferation. Overexpression of wild type Gh in smooth muscle cell line DDT1-MF2 increased 1-AR-induced [³H]thymidine incorporation. A similar response was obtained in cells expressing the transglutaminase inactive mutant (C277S) of Gh. Together, these findings underscore the role of Gh as signal transducer of 1-AR-induced smooth muscle cell proliferation. In this context, pregnant rat myometrium provides an interesting physiological model to study the mechanisms underlying the regulation of the GTPase function of Gh

Received for publication, December 30, 2003 , and in revised form, January 23, 2004.

^* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

To whom correspondence should be addressed. Present address: Institut Pasteur, Département de Biologie du Développement, Bâtiment Jacques Monod, 25, rue du Docteur Roux, 75724 Paris CEDEX 15, France. Tel.: 331-45-68-84-96; Fax: 331-40-61-31-09; E-mail: smhaouty{at}pasteur.fr.

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				M Dupuis, E Houdeau, and S Mhaouty-Kodja Increased potency of {alpha}1-adrenergic receptors to induce inositol phosphates production correlates with the up-regulation of {alpha}1d/Gh{alpha}/phospholipase C{delta}1 signaling pathway in term rat myometrium Reproduction, January 1, 2008; 135(1): 55 - 62. [Abstract] [Full Text] [PDF]

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