E3泛素转移酶连接蛋白SPOP介导的PrLZ泛素化及降解调控去势抵抗性前列腺癌进展的分子机制研究

去势抵抗性前列腺癌（CRPC）的发生与进展一直是泌尿外科临床上治疗的难点。我们既往发现前列腺组织特异性基因PrLZ可调控雄激素受体（AR）进而介导CRPC的发生及进展，但是PrLZ在CRPC中处于高活化状态的分子机制仍不清楚。我们前期研究发现：①E3泛素转移酶连接蛋白SPOP可介导PrLZ泛素化及降解；②PrLZ与SPOP的相互作用不依赖于AR；③ERK1可与PrLZ相互作用。基于此，我们提出“CRPC阶段ERK1/2的持续活化导致PrLZ泛素化降解受阻，SPOP基因突变进一步促进了PrLZ的异常堆积，进而促进CRPC的进展”的理论设想。本项目以SPOP在前列腺癌里的高突变率为临床切入点，拟采用细胞分子生物学技术等研究策略，阐明ERK1磷酸化PrLZ在SPOP介导的PrLZ泛素化及降解过程中的作用，为揭示CRPC进展的机制以及开发靶向PrLZ联合ERK抑制剂治疗CRPC的策略奠定实验依据。

Progression to castration resistant prostate cancer (CRPC) is associated with deterioration in quality of life, and few therapeutic options are currently available. It’s thus urgently needed to clarify the molecular mechanisms. Our previous study found that, PrLZ, a newly identified Prostate Leucine Zipper gene that was highly expressed in PCa could interact with the androgen receptor (AR) directly leading to enhance AR transactivation in the castration-resistant condition. However, the molecular mechanism of consistent activation of PrLZ in CRPC is still unclear. SPOP (speckle-type POZ protein) gene encodes a substrate recognition subunit of the CULLIN3-RBX1 E3 ubiquitin ligase complex. SPOP is the most frequently mutated gene in primary prostate cancer. In our preliminary study, we identified PrLZ as a novel SPOP interactor. Interaction between PrLZ and SPOP lead to the ubiquitination and proteasomal degradation of PrLZ. Interestingly, the interaction between PrLZ and SPOP is AR-independent. More importantly, we observed the enrichment and activation of MEK/ERK pathway in CRPC patients with SPOP mutation. Furthermore, we found the interaction between PrLZ and ERK1. Based on our preliminary data, we hypothesized that constitute activation of ERK1/2 in the castration-resistant stage resulted in blockade of interaction between SPOP and PrLZ, leading to the failure of proteasomal degradation of PrLZ. Mutation of SPOP in CRPC patients further accelerated the accumulation and activation of PrLZ, which then facilitated the progression of CRPC. To further elucidate the regulatory mechanisms of PrLZ by SPOP in CRPC, we aimed to investigate the role MEK/ERK1 signaling played in SPOP-mediated proteasomal degradation of PrLZ. Human prostate cancer cell lines with different expression of PrLZ or SPOP and nude mice subcutaneous xenografts model will served as the model systems in vitro and in vivo. Methods including western blotting, immunoprecipitation, in vitro kinase assay and immunohistochemistry assay will be used in this project. Our study will provide a rationale for the better understanding of molecular mechanisms that regulated SPOP-mediated proteasomal degradation of PrLZ in the progression of CRPC. Targeting PrLZ and ERK1 signaling may provide a new treatment option against CRPC.