HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 282, Issue 7, 4354-4363, February 16, 2007

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 282/7/4354    most recent M609676200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Sarto-Jackson, I. Articles by Sieghart, W. Search for Related Content PubMed PubMed Citation Articles by Sarto-Jackson, I. Articles by Sieghart, W. Social Bookmarking                      What's this?

Spontaneous Cross-link of Mutated 1 Subunits during GABA_A Receptor Assembly^*

Isabella Sarto-Jackson, Roman Furtmueller, Margot Ernst, Sigismund Huck, and Werner Sieghart¹

From the Division of Biochemistry and Molecular Biology, Center for Brain Research, Medical University of Vienna and Section of Biochemical Psychiatry, University Clinic for Psychiatry, A-1090 Vienna, Austria

-Aminobutyric acid, type A (GABA_A) receptor 1 subunits containing a cysteine mutation at a position in the channel mouth (H109C) surprisingly formed a spontaneous cross-link with each other in receptors composed of 1H109C, 3, and 2 subunits. Cross-linking of two 1H109C subunits did not significantly change the affinity of [³H]muscimol or [³H]Ro15-1788 binding in 1H109C32 receptors, but GABA displayed a reduced potency for activating chloride currents. On reduction of the disulfide bond, however, GABA activation as well as diazepam modulation was similar in mutated and wild-type receptors, suggesting that these receptors exhibited the same subunit stoichiometry and arrangement. Disulfide bonds could not be reoxidized by copper phenanthroline after having been reduced in completely assembled receptors, suggesting that cross-linking can only occur at an early stage of assembly. The cross-link of 1H109C subunits and the subsequent transport of the resulting homodimers to the cell surface caused a reduction of the intracellular pool of 1H109C subunits and a reduced formation of completely assembled receptors. The formation of 1H109C homodimers as well as of correctly assembled GABA_A receptors containing cross-linked 1H109C subunits could indicate that homodimerization of 1 subunits via contacts located in the channel mouth might be one starting point of GABA_A receptor assembly. Alternatively the assembly mechanism might have started with the formation of heterodimers followed by a cross-link of mutated 1 subunits at the heterotrimeric stage. The formation of cross-linked 1H109C homodimers would then have occurred independently in a separate pathway.

Received for publication, October 13, 2006 , and in revised form, November 10, 2006.

^* This work was supported by Austrian Science Fund Grant P15165. 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.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. 1.

¹ To whom correspondence should be addressed: Division of Biochemistry and Molecular Biology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090 Vienna, Austria. Tel.: 43-1-4277-62950; Fax: 43-1-4277-62959; E-mail: werner.sieghart{at}meduniwien.ac.at.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?