This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow E-mail this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Xiao, Y.
Right arrow Articles by Phillips, M. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Xiao, Y.
Right arrow Articles by Phillips, M. A.

 Previous Article  |  Next Article 

Eukaryotic Cell, May 2009, p. 747-755, Vol. 8, No. 5
1535-9778/09/$08.00+0     doi:10.1128/EC.00047-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

RNA Interference-Mediated Silencing of Ornithine Decarboxylase and Spermidine Synthase Genes in Trypanosoma brucei Provides Insight into Regulation of Polyamine Biosynthesis{triangledown}

Yanjing Xiao,1 Diane E. McCloskey,2 and Margaret A. Phillips1*

Dept. of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Rd., Dallas, Texas 75390-9041,1 Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, Pennsylvania 170332

Received 8 February 2009/ Accepted 15 March 2009

Polyamine biosynthesis is a drug target for the treatment of African sleeping sickness; however, mechanisms regulating the pathway in Trypanosoma brucei are not well understood. Recently, we showed that RNA interference (RNAi)-mediated gene silencing or the inhibition of S-adenosylmethionine decarboxylase (AdoMetDC) led to the upregulation of the AdoMetDC activator, prozyme, and ornithine decarboxylase (ODC) proteins. To determine if this regulatory response is specific to AdoMetDC, we studied the effects of the RNAi-induced silencing of the spermidine synthase (SpdSyn) and ODC genes in bloodstream form T. brucei. The knockdown of either gene product led to the depletion of the polyamine and trypanothione pools and to cell death. Decarboxylated AdoMet levels were elevated, while AdoMet was not affected. There was no significant effect on the protein levels of other polyamine pathway enzymes. The treatment of parasites with the ODC inhibitor {alpha}-difluoromethylornithine gave similar results to those observed for ODC knockdown. Thus, the cellular response to the loss of AdoMetDC activity is distinctive, suggesting that AdoMetDC activity controls the expression levels of the other spermidine biosynthetic enzymes. RNAi-mediated cell death occurred more rapidly for ODC than for SpdSyn. Further, the ODC RNAi cells were rescued by putrescine, but not spermidine, suggesting that the depletion of both putrescine and spermidine is more detrimental than the depletion of spermidine alone. This finding may contribute to the effectiveness of ODC as a target for the treatment of African sleeping sickness, thus providing important insight into the mechanism of action of a key antitrypanosomal agent.

* Corresponding author. Mailing address: Dept. of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Rd., Dallas, TX 75390-9041. Phone: (214) 645-6164. Fax: (214) 645-6166. E-mail: margaret.phillips{at}UTSouthwestern.edu

{triangledown} Published ahead of print on 20 March 2009.

Eukaryotic Cell, May 2009, p. 747-755, Vol. 8, No. 5
1535-9778/09/$08.00+0     doi:10.1128/EC.00047-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2010 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»