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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Arsenates / pharmacology
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COS Cells
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Chlorocebus aethiops
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Cytoplasmic Granules / genetics
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Cytoplasmic Granules / metabolism*
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Endoribonucleases / genetics
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Endoribonucleases / metabolism
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Guanine Nucleotide Exchange Factors / genetics
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Guanine Nucleotide Exchange Factors / metabolism*
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Humans
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Jurkat Cells
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Phosphorylation / drug effects
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Phosphorylation / physiology
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Protein Biosynthesis / drug effects
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Protein Biosynthesis / physiology
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Protein Structure, Tertiary
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Protein Synthesis Inhibitors / pharmacology
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism*
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Puromycin / pharmacology
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RNA Stability / drug effects
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RNA Stability / physiology
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
Substances
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Arsenates
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DEF6 protein, human
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DNA-Binding Proteins
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Guanine Nucleotide Exchange Factors
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Nuclear Proteins
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Protein Synthesis Inhibitors
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RNA, Messenger
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Puromycin
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sodium arsenate
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Protein-Tyrosine Kinases
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emt protein-tyrosine kinase
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Endoribonucleases
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DCP1b protein, human