BACKGROUND LRP5/6 are co-receptors in Wnt/β-catenin pathway. Recently, we discovered multiple β-catenin independent functions of LRP5/6 in tumor cells and in the diseased heart. Nucleoporin 37 (NUP37) is an important component of the nuclear pore complex (NPC), whose elevated expression is associated with worsened prognosis in liver cancer. Previous studies have shown that NUP37 interacted with YAP and activated YAP/TEAD signaling in liver cancer. Our preliminary findings showed a nuclear location of LRP5. We thus tested the hypothesis that LRP5 may act as a genuine regulator of YAP/TEAD signaling via modulating NUP37 in a β-catenin-independent way. METHODS We performed siRNA knockdown of LRP5, LRP6, or β-catenin in liver cancer HepG2 cells to determine the effect on tumor cell proliferation. Protein expressions and interaction between LRP5 and NUP37 were determined using immunoprecipitation and western blot analyses. RESULTS HepG2 cell proliferation was markedly inhibited by knockdown of LRP5 but not LRP6 or β-catenin, suggesting that LRP5 has a specific, β-catenin-independent role in inhibiting HepG2 cell proliferation. Knockdown of NUP37 by siRNA inhibited the proliferation of HepG2 cells, whereas overexpression of NUP37 reversed the decrease in cell proliferation induced by LRP5 knockdown. Immunoprecipitation assays confirmed that LRP5 bound to NUP37. Furthermore, LRP5 overexpression restored NUP37 knockdown-induced downregulation of YAP/TEAD pathway. CONCLUSIONS LRP5 deletion attenuates cell proliferation via destabilization of NUP37, in a β-catenin-independent manner. LRP5 therefore acts as a genuine regulator of YAP/TEAD signaling via maintaining the integrity of the NPC, and implicates a therapeutic strategy in targeting LRP5 for inhibiting liver cancer cell proliferation.

中文翻译：

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低密度脂蛋白相关受体5的缺失通过使Nucleoporin 37不稳定来抑制肝癌细胞的增殖。

背景LRP5 / 6是Wnt /β-catenin途径的共受体。最近，我们在肿瘤细胞和患病心脏中发现了LRP5 / 6的多个不依赖β-catenin的功能。核蛋白37（NUP37）是核孔复合物（NPC）的重要组成部分，其表达升高与肝癌预后恶化相关。先前的研究表明，NUP37与YAP相互作用并激活了肝癌中的YAP / TEAD信号传导。我们的初步发现显示LRP5处于核位置。因此，我们检验了以下假设：LRP5可以通过以β-catenin独立的方式调节NUP37充当YAP / TEAD信号的真正调节剂。方法我们对肝癌HepG2细胞中的LRP5，LRP6或β-catenin进行了siRNA敲低以确定对肿瘤细胞增殖的影响。使用免疫沉淀和蛋白质印迹分析确定LRP5和NUP37之间的蛋白表达和相互作用。结果LRP5的敲低可显着抑制HepG2细胞的增殖，而LRP6或β-catenin则无此抑制作用，这表明LRP5在抑制HepG2细胞的增殖中具有非β-catenin特异的作用。siRNA敲低NUP37抑制了HepG2细胞的增殖，而NUP37的过表达逆转了LRP5敲低诱导的细胞增殖的减少。免疫沉淀测定法证实LRP5与NUP37结合。此外，LRP5过表达恢复了NUP37敲低诱导的YAP / TEAD途径的下调。结论LRP5缺失通过NUP37失稳以β-catenin独立的方式减弱了细胞的增殖。