title: Phosphorylation of Serine 148 in Giardia lamblia End-binding 1 Protein is Important for Cell Division.
abstract: Giardia lamblia is a unicellular organism, showing a polarity with two nuclei and cytoskeletal structures. Accurate positioning of these organelles is essential for division of G. lamblia, which is poorly understood. Giardia lamblia end-binding 1 (GlEB1) protein and G. lamblia aurora kinase (GlAK) have been shown to modulate microtubule (MT) distribution during cytokinesis. A direct association between GlEB1 and GlAK was demonstrated. Like GlEB1, GlAK was also found at nuclear envelopes and median bodies of G. lamblia. In vitro kinase assays using Giardia lysates immunoprecipitated with anti-GlAK antibodies or recombinant GlAK suggested that GlEB1 is a substrate of GlAK. Site-directed mutagenesis indicated that threonine-205 in GlAK was auto-phosphorylated and that GlAK phosphorylated serine (Ser)-148 in GlEB1. Ectopic expression of a mutant GlEB1 (with conversion of Ser-148 into alanine of GlEB1) resulted in an increased number of Giardia cells with division defects. Treatment of G. lamblia with an AK inhibitor triggered cytokinesis defects, and ectopic expression of a phospho-mimetic mutant GlEB1 (with conversion of Ser-148 into aspartate) rescued the defects in Giardia cell division caused by the AK inhibitor. These results suggested that phosphorylation of GlEB1 played a role in cytokinesis in G. lamblia.
authors.affiliation: Department of Environmental Medical Biology and Institute of Tropical Medicine, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, 03722, South Korea.
authors.forename: Juri
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Environmental Medical Biology and Institute of Tropical Medicine, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, 03722, South Korea.
authors.forename: Hye-Yeon
authors.initials: HY
authors.lastname: Lee
authors.affiliation: Department of Life Science, Sogang University, Seoul, 04107, South Korea.
authors.forename: Kyu-Ho
authors.initials: KH
authors.lastname: Lee
authors.affiliation: Department of Environmental Medical Biology and Institute of Tropical Medicine, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, 03722, South Korea.
authors.forename: Soon-Jung
authors.initials: SJ
authors.lastname: Park
mesh_terms: D064127:Aurora Kinases / Q000378:metabolism*; D048749:Cytokinesis / Q000187:drug effects; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D016829:Giardia lamblia / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D009685:Nuclear Envelope / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism*
chemical_list: D003598:Cytoskeletal Proteins; D047428:Protein Kinase Inhibitors; D015800:Protozoan Proteins; D012694:Serine; D064127:Aurora Kinases
keywords: Aurora kinase; cell cycle; cytokinesis; division defect; mutagenesis