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
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
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DOI：
10.1074/jbc.m112.346767
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发表时间：
2012-09-07
影响因子：
4.8
通讯作者：
Sablitzky, Fred
中科院分区：
文献类型：
--
作者：
Hey, Fiona;Czyzewicz, Nathan;Sablitzky, Fred
DEF 6（SLAT/IBP），一个Rho家族鸟嘌呤核苷酸交换因子，定位到免疫突触的中心依赖于ITK，一个Tec家族激酶，其调节T细胞信号传导途径和Cdc 42依赖性肌动蛋白聚合的组分的时空组织。在这里，我们证明了ITK既与DEF 6相互作用，又在酪氨酸残基Tyr（210）和Tyr（222）处磷酸化DEF 6。GFP标记的Y210 E-Y222 E磷酸模拟物的表达导致DEF 6细胞质颗粒的形成，其与P体的标记物脱帽酶1（DCP 1）共定位; mRNA降解的位点。类似地，用嘌呤霉素或亚砷酸钠（阻止翻译的试剂）处理细胞也导致DEF 6在细胞质颗粒中积累。生物信息学分析确定了一个富含谷氨酰胺的七重重复区域;这是一种聚集蛋白的特征，位于DEF 6的C-末端区域内，具有通过磷酸化依赖性暴露该区域来促进颗粒形成的潜力。这些数据表明，除了其作为GEF的作用外，DEF 6还可能在调节mRNA翻译中起作用。
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.