Nishino Tasuku, Matsunaga Ryota, Konishi Hiroaki
Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Shobara, Hiroshima 727-0023, Japan.
Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Shobara, Hiroshima 727-0023, Japan.
Biochem Biophys Res Commun. 2015 Aug 21;464(2):616-21. doi: 10.1016/j.bbrc.2015.07.024. Epub 2015 Jul 9.
GAREM1 (Grb2-associated regulator of Erk/MAPK1) is an adaptor protein that is involved in the epidermal growth factor (EGF) pathway. The nuclear localization of GAREM1 depends on the nuclear localization sequence (NLS), which is located at the N-terminal CABIT (cysteine-containing, all in Themis) domain. Here, we identified 14-3-3ε as a GAREM-binding protein, and its binding site is closely located to the NLS. This 14-3-3 binding site was of the atypical type and independent of GAREM phosphorylation. Moreover, the binding of 14-3-3 had an effect on the nuclear localization of GAREM1. Unexpectedly, we observed that the CABIT domain had intramolecular association with the C-terminal SAM (sterile alpha motif) domain. This association might be inhibited by binding of 14-3-3 at the CABIT domain. Our results demonstrate that the mechanism underlying the nuclear localization of GAREM1 depends on its NLS in the CABIT domain, which is controlled by the binding of 14-3-3 and the C-terminal SAM domain. We suggest that the interplay between 14-3-3, SAM domain and CABIT domain might be responsible for the distribution of GAREM1 in mammalian cells.
GAREM1（Grb2相关的Erk/MAPK1调节因子）是一种衔接蛋白，参与表皮生长因子（EGF）信号通路。GAREM1的核定位依赖于位于N端CABIT（含半胱氨酸，全在Themis中）结构域的核定位序列（NLS）。在此，我们鉴定出14-3-3ε是一种GAREM结合蛋白，其结合位点紧邻NLS。该14-3-3结合位点属于非典型类型，且不依赖于GAREM的磷酸化。此外，14-3-3的结合对GAREM1的核定位有影响。出乎意料的是，我们观察到CABIT结构域与C端SAM（无活性α基序）结构域存在分子内相互作用。这种相互作用可能会被14-3-3在CABIT结构域的结合所抑制。我们的结果表明，GAREM1核定位的机制依赖于其位于CABIT结构域的NLS，而这受到14-3-3和C端SAM结构域结合的调控。我们认为，14-3-3、SAM结构域和CABIT结构域之间的相互作用可能决定了GAREM1在哺乳动物细胞中的分布。
