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Eukaryotic Cell, July 2007, p. 1108-1118, Vol. 6, No. 7
1535-9778/07/$08.00+0     doi:10.1128/EC.00107-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Phosphatidylinositol 4-Kinase III-ß Is Required for Golgi Maintenance and Cytokinesis in Trypanosoma brucei{triangledown}

Melissa J. Rodgers, Joseph P. Albanesi, and Margaret A. Phillips*

Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041

Received 4 April 2007/ Accepted 28 April 2007

The parasitic protozoan Trypanosoma brucei contains two type III phosphatidylinositol 4-kinases ({alpha} and ß). We have cloned the gene encoding the T. brucei type III phosphatidylinositol 4-kinase ß (TbPI4KIII-ß), expressed the protein in COS-7 cells, and confirmed that the protein catalyzes the phosphorylation of phosphatidylinositol. Depletion of TbPI4KIII-ß in procyclic T. brucei by RNA interference (RNAi) resulted in inhibition of cell growth and a distorted cellular morphology. RNAi cells had a distorted Golgi apparatus, and lysosomal and flagellar pocket proteins were mislocalized. Ultrastructural analysis revealed the internal accumulation of a heterogeneous population of vesicles, abnormal positioning of organelles, and a loss of cell polarity. Scanning electron microcopy revealed a twisted phenotype, and dividing cells often exhibited a detached daughter flagellum and lacked a cleavage furrow. Cell cycle analysis confirmed that cells depleted of TbPI4KIII-ß have a postmitotic cytokinesis block that occurs after a single round of mitosis, suggestive of a specific cell cycle block. In summary, TbPI4KIII-ß is an essential protein in procyclic T. brucei, required for maintenance of Golgi structure, protein trafficking, normal cellular shape, and cytokinesis.

* Corresponding author. Mailing address: Department of Pharmacology, University of Texas Southwestern Medical Center, 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 4 May 2007.

Eukaryotic Cell, July 2007, p. 1108-1118, Vol. 6, No. 7
1535-9778/07/$08.00+0     doi:10.1128/EC.00107-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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