Modulation of Wnt signaling by the nuclear localization of cellular FLIP-L
Modulation of Wnt signaling by the nuclear localization of cellular FLIP-L
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DOI：
10.1242/jcs.058602
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发表时间：
2010-01-01
影响因子：
4
通讯作者：
Naito, Mikihiko
中科院分区：
文献类型：
--
作者：
Katayama, Ryohei;Ishioka, Toshiyasu;Naito, Mikihiko
细胞FLIP（cFLIP）抑制由死亡受体连接引发的凋亡信号传导。我们先前报道了长形式的cFLIP（cFLIP-L）通过抑制β-连环蛋白泛素化来增强Wnt信号传导。在这份报告中，我们提出的证据表明，cFLIP-L易位到细胞核中，这可能有一个Wnt信号的调制作用。cFLIP-L在C末端具有功能性二分核定位信号（NLS）。野生型cFLIP-L（wt-FLIP-L）定位于细胞核和细胞质中，而NLS突变的cFLIP-L主要定位于细胞质中。cFLIP-L在NLS附近也有核输出信号（内斯），CRM 1依赖性核输出的抑制剂来普霉素B增加cFLIP-L的核积累，表明其穿梭于细胞核和细胞质之间。在NLS和内斯中具有缺失或突变的突变cFLIP-L蛋白的表达赋予对Fas介导的细胞凋亡的抗性，如wt-FLIP-L，但它们不增强Wnt信号传导，这表明cFLIP-L的C-末端在Wnt信号传导调节中的重要作用。当wt-FLIP-L通过与外源性内斯缀合（NES-FLIP-L）在细胞质中表达时，Wnt信号传导不增强，而NES-FLIP-L增加细胞质。cFLIP-L与Wnt信号转导的报告质粒物理相互作用，但不与对照质粒相互作用。这些结果表明核cFLIP-L在Wnt信号传导的调节中的作用。
Cellular FLIP (cFLIP) inhibits the apoptosis signaling initiated by death receptor ligation. We previously reported that a long form of cFLIP (cFLIP-L) enhances Wnt signaling via inhibition of beta-catenin ubiquitylation. In this report, we present evidence that cFLIP-L translocates into the nucleus, which could have a role in modulation of Wnt signaling. cFLIP-L has a functional bipartite nuclear localization signal (NLS)at the C-terminus. Wild-type cFLIP-L (wt-FLIP-L) localizes in both the nucleus and cytoplasm, whereas NLS-mutated cFLIP-L localizes predominantly in the cytoplasm. cFLIP-L also has a nuclear export signal (NES) near the NLS, and leptomycin B, an inhibitor of CRM1-dependent nuclear export, increases the nuclear accumulation of cFLIP-L, suggesting that it shuttles between the nucleus and cytoplasm. Expression of mutant cFLIP-L proteins with a deletion or mutations in the NLS and NES confers resistance to Fas-mediated apoptosis, as does wt-FLIP-L, but they do not enhance Wnt signaling, which suggests an important role of the C-terminus of cFLIP-L in Wnt-signaling modulation. When wt-FLIP-L is expressed in the cytoplasm by conjugation with exogenous NES (NES-FLIP-L), Wnt signaling is not enhanced, whereas the NES-FLIP-L increases cytoplasmic. beta-catenin as efficiently as wt-FLIP-L.cFLIP-L physically interacts with the reporter plasmid for Wnt signaling, but not with the control plasmid. These results suggest a role for nuclear cFLIP-L in the modulation of Wnt signaling.