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

J. Biol. Chem., Vol. 282, Issue 26, 19122-19132, June 29, 2007

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 282/26/19122    most recent M609915200v1 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 Jin, Q. Articles by Mulder, K. M. Search for Related Content PubMed PubMed Citation Articles by Jin, Q. Articles by Mulder, K. M. Social Bookmarking                      What's this?

Requirement for the Dynein Light Chain km23-1 in a Smad2-dependent Transforming Growth Factor- Signaling Pathway^*

From the Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033

We have identified km23-1 as a novel transforming growth factor- (TGF) receptor (TR)-interacting protein that is also a light chain of the motor protein dynein (dynein light chain). Herein, we demonstrate by sucrose gradient analyses that, in the presence of TGF but not in the absence, km23-1 was present in early endosomes with the TRs. Further, confocal microscopy studies indicate that endogenous km23-1 was co-localized with endogenous Smad2 at early times after TGF treatment, prior to Smad2 translocation to the nucleus. In addition, immunoprecipitation/blot analyses showed that TGF regulated the interaction between endogenous km23-1 and endogenous Smad2 in vivo. Blockade of km23-1 using a small interfering RNA approach resulted in a reduction in both total intracellular Smad2 levels and in nuclear levels of phosphorylated Smad2 after TGF treatment. This decrease was reversed by lactacystin, a specific inhibitor of the 26 S proteasome, suggesting that knockdown of km23-1 causes proteasomal degradation of phosphorylated (i.e. activated) Smad2. Blockade of km23-1 also resulted in a reduction in TGF/Smad2-dependent ARE-Lux transcriptional activity, which was rescued by a km23-1 small interfering RNA-resistant construct. In contrast, a reduction in TGF/Smad3-dependent SBE2-Luc transcriptional activity did not occur under similar conditions. Furthermore, overexpression of the dynactin subunit dynamitin, which is known to disrupt dynein-mediated intracellular transport, blocked TGF-stimulated nuclear translocation of Smad2. Collectively, our findings indicate for the first time that a dynein light chain is required for a Smad2-dependent TGF signaling pathway.

Received for publication, October 23, 2006 , and in revised form, April 3, 2007.

^* The work was supported by National Institutes of Health Grants CA90765, CA92889, and CA100239 (to K. M. M.). 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. S1.

¹ To whom correspondence should be addressed: Dept. of Pharmacology, MC H078, Penn State College of Medicine, 500 University Dr., Hershey, PA 17033. Tel.: 717-531-6789; Fax: 717-531-5013; E-mail: kmm15{at}psu.edu.

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