title: DEF6, a novel substrate for the Tec kinase ITK, contains a glutamine-rich aggregation-prone region and forms cytoplasmic granules that co-localize with P-bodies.
abstract: Localization of DEF6 (SLAT/IBP), a Rho-family guanine nucleotide exchange factor, to the center of the immune synapse is dependent upon ITK, a Tec-family kinase that regulates the spatiotemporal organization of components of T cell signaling pathways and Cdc42-dependent actin polymerization. Here we demonstrate that ITK both interacts with DEF6 and phosphorylates DEF6 at tyrosine residues Tyr(210) and Tyr(222). Expression of a GFP-tagged Y210E-Y222E phosphomimic resulted in the formation of DEF6 cytoplasmic granules that co-localized with decapping enzyme 1 (DCP1), a marker of P-bodies; sites of mRNA degradation. Similarly treatment of cells with puromycin or sodium arsenite, reagents that arrest translation, also resulted in the accumulation of DEF6 in cytoplasmic granules. Bioinformatics analysis identified a glutamine-rich, heptad-repeat region; a feature of aggregating proteins, within the C-terminal region of DEF6 with the potential to promote granule formation through a phosphorylation-dependent unmasking of this region. These data suggest that in addition to its role as a GEF, DEF6 may also function in regulating mRNA translation.
authors: School of Biology, Molecular Cell and Developmental Biology, The University of Nottingham, Nottingham NG7 2UH, United Kingdom.
authors: Fiona
authors: F
authors: Hey
authors: Nathan
authors: N
authors: Czyzewicz
authors: Peter
authors: P
authors: Jones
authors: Fred
authors: F
authors: Sablitzky
mesh_terms: D000818:Animals; D001149:Arsenates / Q000494:pharmacology; D019556:COS Cells; D002522:Chlorocebus aethiops; D003594:Cytoplasmic Granules / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D014176:Protein Biosynthesis / Q000187:drug effects / Q000502:physiology; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011691:Puromycin / Q000494:pharmacology; D020871:RNA Stability / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D001149:Arsenates; C479750:DEF6 protein, human; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D011691:Puromycin; C009277:sodium arsenate; D011505:Protein-Tyrosine Kinases; C080813:emt protein-tyrosine kinase; D004722:Endoribonucleases; C489698:DCP1b protein, human