Cho Hyo Min, Kim Joo Yeon, Kim Hyun, Sun Woong
Department of Anatomy, Brain Korea 21, Korea University College of Medicine, Anam-Dong, Sungbuk-Gu, Seoul, 136-705, Korea.
Histochem Cell Biol. 2014 Oct;142(4):411-9. doi: 10.1007/s00418-014-1220-3. Epub 2014 Apr 20.
Phosphatase and actin regulator 4 (Phactr4) is a newly discovered protein that inhibits protein phosphatase 1 and shows actin-binding activity. We previously found that Phactr4 is expressed in the neurogenic niche in adult mice, although its precise subcellular localization and possible function in neural stem cells (NSCs) is not yet understood. Here, we show that Phactr4 formed punctiform clusters in the cytosol of subventricular zone-derived adult NSCs and their progeny in vitro. These Phactr4 signals were not associated with F-actin fibers but were closely associated with intermediate filaments such as nestin and glial fibrillary acidic protein (GFAP) fibers. Direct binding of Phactr4 with nestin and GFAP filaments was demonstrated using Duolink protein interaction analyses and immunoprecipitation assays. Interestingly, when nestin fibers were de-polymerized during the mitosis or by the phosphatase inhibitor, Phactr4 appeared to be dissociated from nestin, suggesting that their protein interaction is regulated by the protein phosphorylation. These results suggest that Phactr4 forms functional associations with intermediate filament networks in adult NSCs.
磷酸酶与肌动蛋白调节因子4（Phactr4）是一种新发现的蛋白，它能抑制蛋白磷酸酶1并具有肌动蛋白结合活性。我们之前发现Phactr4在成年小鼠的神经发生微环境中表达，但其在神经干细胞（NSC）中的确切亚细胞定位及可能的功能尚不清楚。在此，我们表明Phactr4在体外源自脑室下区的成年神经干细胞及其子代细胞的胞质溶胶中形成点状簇。这些Phactr4信号与F-肌动蛋白纤维无关，但与诸如巢蛋白和胶质纤维酸性蛋白（GFAP）纤维等中间丝密切相关。使用Duolink蛋白相互作用分析和免疫沉淀试验证明了Phactr4与巢蛋白和GFAP丝的直接结合。有趣的是，当巢蛋白纤维在有丝分裂期间或通过磷酸酶抑制剂解聚时，Phactr4似乎与巢蛋白解离，这表明它们的蛋白相互作用受蛋白磷酸化调节。这些结果表明Phactr4在成年神经干细胞中与中间丝网络形成功能关联。
