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

J. Biol. Chem., Vol. 282, Issue 34, 24650-24659, August 24, 2007

This Article Full Text Full Text (PDF) All Versions of this Article: 282/34/24650    most recent M703167200v1 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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Wang, W. Articles by Torti, F. M. Search for Related Content PubMed PubMed Citation Articles by Wang, W. Articles by Torti, F. M. Social Bookmarking                      What's this?

Excess Capacity of the Iron Regulatory Protein System^*

Wei Wang, Xiumin Di, Ralph B. D'Agostino, Jr.^||, Suzy V. Torti^¶1, and Frank M. Torti

From the Departments of Cancer Biology, ^||Public Health Sciences, and ^¶Biochemistry and the Comprehensive Cancer Center, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27157

Iron regulatory proteins (IRP1 and IRP2) are master regulators of cellular iron metabolism. IRPs bind to iron-responsive elements (IREs) present in the untranslated regions of mRNAs encoding proteins of iron storage, uptake, transport, and export. Because simultaneous knockout of IRP1 and IRP2 is embryonically lethal, it has not been possible to use dual knockouts to explore the consequences of loss of both IRP1 and IRP2 in mammalian cells. In this report, we describe the use of small interfering RNA to assess the relative contributions of IRP1 and IRP2 in epithelial cells. Stable cell lines were created in which either IRP1, IRP2, or both were knocked down. Knockdown of IRP1 decreased IRE binding activity but did not affect ferritin H and transferrin receptor 1 (TfR1) expression, whereas knockdown of IRP2 marginally affected IRE binding activity but caused an increase in ferritin H and a decrease in TfR1. Knockdown of both IRPs resulted in a greater reduction of IRE binding activity and more severe perturbation of ferritin H and TfR1 expression compared with single IRP knockdown. Even though the knockdown of IRP-1, IRP-2, or both was efficient, resulting in nondetectable protein and under 5% of wild type levels of mRNA, all stable knockdowns retained an ability to modulate ferritin H and TfR1 appropriately in response to iron challenge. However, further knockdown of IRPs accomplished by transient transfection of small interfering RNA in stable knockdown cells completely abolished the response of ferritin H and TfR1 to iron challenge, demonstrating an extensive excess capacity of the IRP system.

Received for publication, April 16, 2007 , and in revised form, May 29, 2007.

^* This work was supported by National Institutes of Health Grant R37 DK42412 (to F. M. T.). 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.

¹ To whom correspondence should be addressed: Dept. of Biochemistry, Wake Forest University Health Sciences, Winston Salem, NC 27157. Tel.: 336-716-9357; Fax: 336-716-0255; E-mail: storti{at}wfubmc.edu.

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

This article has been cited by other articles:

				Y. Jiao, J. Wilkinson IV, X. Di, W. Wang, H. Hatcher, N. D. Kock, R. D'Agostino Jr, M. A. Knovich, F. M. Torti, and S. V. Torti Curcumin, a cancer chemopreventive and chemotherapeutic agent, is a biologically active iron chelator Blood, January 8, 2009; 113(2): 462 - 469. [Abstract] [Full Text] [PDF]

				F. Zhang, W. Wang, Y. Tsuji, S. V. Torti, and F. M. Torti Post-transcriptional Modulation of Iron Homeostasis during p53-dependent Growth Arrest J. Biol. Chem., December 5, 2008; 283(49): 33911 - 33918. [Abstract] [Full Text] [PDF]

				C. O. dos Santos, L. C. Dore, E. Valentine, S. G. Shelat, R. C. Hardison, M. Ghosh, W. Wang, R. S. Eisenstein, F. F. Costa, and M. J. Weiss An Iron Responsive Element-like Stem-Loop Regulates {alpha}-Hemoglobin-stabilizing Protein mRNA J. Biol. Chem., October 3, 2008; 283(40): 26956 - 26964. [Abstract] [Full Text] [PDF]

				M. C. Sammarco, S. Ditch, A. Banerjee, and E. Grabczyk Ferritin L and H Subunits Are Differentially Regulated on a Post-transcriptional Level J. Biol. Chem., February 22, 2008; 283(8): 4578 - 4587. [Abstract] [Full Text] [PDF]