泛素相关蛋白UBAP2L通过Hippo信号通路调控膀胱癌细胞生长的功能及机制研究

Bladder cancer is the most common tumor type in urinary system, which has no effective therapeutic target at present. While screening for novel potential targets in bladder cancer, our group discovered ubiquitin associated protein UBAP2L functioned as a bladder cancer regulator which highly expressed in bladder cancer cells. Yet how UBAP2L regulated bladder cancer cell growth was unknown. In our previous studies, we found that knockdown of UBAP2L was able to inhibit bladder cancer cell growth via downregulating the downstream target genes' expression of Hippo signaling pathway and further repress YAP overexpression induced bladder cancer cell overgrowth; UBAP2L interacted with scaffold protein Sav1 and affected its protein stability, so that activated YAP activity. Therefore, we hypothesized that UBAP2L regulated YAP activity via ubiquitinating to degrade Sav1 protein，so that activated YAP to accelerate bladder cancer growth. This project plans to clarify the function of UBAP2L on bladder cancer growth via Sav1's effect on YAP in vitro and in vivo; identify the Ub sites affected by UBAP2L via in vitro Ub assay and mass spectrometry (MS) analysis; study the molecular mechanism of UBAP2L regulatory effect on YAP activity. This project connected the function of UBAP2L with YAP and Sav1 and might offer novel targets for bladder cancer diagnosis and therapy.

膀胱癌是泌尿系统最常见的肿瘤，目前尚无有效的治疗靶点。本团队在筛选膀胱癌新靶点时发现泛素相关蛋白UBAP2L在膀胱癌中高表达且调控膀胱癌生长，但分子机制尚不明晰。申报人近期发现敲低UBAP2L下调Hippo信号通路下游控制细胞生长及迁移的靶基因（CTGF、cyr61等）表达以抑制膀胱癌生长，进而阻断YAP过表达引起的细胞过生长；UBAP2L通过与支架蛋白Sav1相互作用，影响Sav1蛋白稳定性以激活YAP。因此，我们推测UBAP2L通过泛素化降解Sav1蛋白调控YAP活性进而促进膀胱癌生长。本项目拟利用体内外实验研究UBAP2L通过Sav1影响YAP活性调控膀胱癌生长的功能；体外泛素化实验和质谱分析鉴定UBAP2L泛素化Sav1的作用位点；从亚细胞定位和蛋白相互作用等方面研究UBAP2L调控YAP活性的分子机制。本项目拟将UBAP2L与YAP、Sav1功能联系起来，为膀胱癌诊治寻找新靶点。

膀胱癌是常见的泌尿系统恶性肿瘤，寻找有效的治疗靶点十分必要。高度保守的Hippo信号通路与多种肿瘤的发生发展密切相关，然而此通路在膀胱癌中的功能和机制尚不明晰，有待深入研究以寻找新的药物治疗靶点。我们的研究发现：（1）在筛选膀胱癌新靶点时发现泛素相关蛋白UBAP2L在膀胱癌中高表达且调控膀胱癌生长；（2）通过实验我们发现敲低UBAP2L抑制膀胱癌生长和迁移而UBAP2L过表达可以抑制膀胱癌生长和迁移；（3）进一步的研究表明敲低UBAP2L下调Hippo信号通路下游控制细胞生长及迁移的靶基因（CTGF、cyr61等）表达，进而阻断YAP过表达引起的细胞过生长；（4）UBAP2L通过与支架蛋白Sav1相互作用，影响Sav1蛋白稳定性以激活YAP；（5）通过研究我们发现Hippo信号通路下游YAP转录复合体及其抑制剂维替泊芬(VP)在膀胱癌发生发展中的功能及作用机制；（6）通过靶向Hippo信号通路我们发现了干预膀胱癌的新药物Verteporfin （特异性靶向YAP转录复合体的抑制剂）。综上所述，本研究初步发现了UBAP2L调控YAP活性的分子机制及特异性靶向YAP的抑制剂（Verteporfin，VP）在膀胱癌生长和迁移过程中的作用及可能的分子机制，取得了一定的干预膀胱癌进程的成效。