Phosphatidylinositol 4-kinase III-beta is required for Golgi maintenance and cytokinesis in Trypanosoma brucei.
The parasitic protozoan Trypanosoma brucei contains two type III phosphatidylinositol 4-kinases (alpha and beta). We have cloned the gene encoding the T. brucei type III phosphatidylinositol 4-kinase beta (TbPI4KIII-beta), expressed the protein in COS-7 cells, and confirmed that the protein catalyzes the phosphorylation of phosphatidylinositol. Depletion of TbPI4KIII-beta 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-beta have a postmitotic cytokinesis block that occurs after a single round of mitosis, suggestive of a specific cell cycle block. In summary, TbPI4KIII-beta is an essential protein in procyclic T. brucei, required for maintenance of Golgi structure, protein trafficking, normal cellular shape, and cytokinesis.
Rodgers
Melissa J
MJ
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA.
Albanesi
Joseph P
JP
Phillips
Margaret A
MA
D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002453:Cell Cycle / Q000502:physiology; D048430:Cell Shape; D002522:Chlorocebus aethiops; D048749:Cytokinesis / Q000502:physiology*; D006056:Golgi Apparatus / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010641:Phenotype; D034622:RNA Interference; D016415:Sequence Alignment; D014346:Trypanosoma brucei brucei / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure
D007527:Isoenzymes; D019870:1-Phosphatidylinositol 4-Kinase