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Eukaryotic Cell, September 2007, p. 1618-1624, Vol. 6, No. 9
1535-9778/07/$08.00+0     doi:10.1128/EC.00229-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Choline Induces Transcriptional Repression and Proteasomal Degradation of the Malarial Phosphoethanolamine Methyltransferase{triangledown}

William Harold Witola and Choukri Ben Mamoun*

Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, Connecticut 06030

Received 27 June 2007/ Accepted 9 July 2007

During its intraerythrocytic life cycle, the malaria parasite Plasmodium falciparum undergoes dramatic metabolic and morphological changes and multiplies to produce up to 36 new daughter parasites. This rapid multiplication of the parasite requires an active synthesis of new membranes. The major component of these membranes, phosphatidylcholine, is synthesized via two metabolic routes, the CDP-choline pathway, which uses host choline as a precursor, and the plant-like serine decarboxylase-phosphoethanolamine methyltransferase (SDPM) pathway, which uses host serine as a precursor. Here we provide evidence indicating that the activity of the SDPM pathway is regulated by the CDP-choline precursor, choline. We show that the phosphoethanolamine methyltransferase, Pfpmt, a critical enzyme in the SDPM pathway, is down-regulated at the transcriptional level as well as targeted for degradation by the proteasome in the presence of choline. Transcript analysis revealed that PfPMT transcription is repressed by choline in a dose-dependent manner. Immunoblotting, pulse-chase experiments, and immunoprecipitation studies demonstrated that Pfpmt degradation occurs not only in wild-type but also in transgenic parasites constitutively expressing Pfpmt. The proteasome inhibitor bortezomib inhibited choline-mediated Pfpmt degradation. These data provide the first evidence for metabolite-mediated transcriptional and proteasomal regulation in Plasmodium and will set the stage for the use of this system for conditional gene and protein expression in this organism.

* Corresponding author. Mailing address: Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT 06030-3301. Phone: (860) 679-3544. Fax: (860) 679-8345. E-mail: choukri{at}up.uchc.edu

{triangledown} Published ahead of print on 20 July 2007.

Eukaryotic Cell, September 2007, p. 1618-1624, Vol. 6, No. 9
1535-9778/07/$08.00+0     doi:10.1128/EC.00229-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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  • Witola, W. H., El Bissati, K., Pessi, G., Xie, C., Roepe, P. D., Mamoun, C. B. (2008). Disruption of the Plasmodium falciparum PfPMT Gene Results in a Complete Loss of Phosphatidylcholine Biosynthesis via the Serine-Decarboxylase-Phosphoethanolamine-Methyltransferase Pathway and Severe Growth and Survival Defects. J. Biol. Chem. 283: 27636-27643 [Abstract] [Full Text]  
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