Ao Ning, Liu Yanyan, Feng Hailiang, Bian Xiaocui, Li Zhanwen, Gu Bei, Zhao Xiaomei, Liu Yuqin
Department of Pathology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Tsinghua University, Beijing, China.
Cell Physiol Biochem. 2014;33(6):1863-75. doi: 10.1159/000362964. Epub 2014 Jun 23.
BACKGROUND/AIMS: The ubiquitin-specific peptidase USP22 mediates various cellular and organismal processes, such as cell growth, apoptosis, and tumor malignancy. However, the molecular mechanisms that regulate USP22 activity remain poorly understood. Here we identify STAT3 as a new USP22 interactor.
· We used western blotting and RT-PCR to measure key protein, acetylated STAT3, and mRNA levels in HEK293 and colorectal cancer cell lines transfected with expression plasmids or specific siRNAs. Co-immunoprecipitation was used to demonstrate protein-protein interaction and protein complex composition.
USP22 overexpression down-regulated STAT3 acetylation by deubiquitinating SIRT1. The three proteins were found to be present in a single protein complex. SiRNA-mediated depletion of endogenous USP22 resulted in SIRT1 destabilization and elevated STAT3 acetylation. Consistent with this finding, USP22 also down-regulated the expression of two known STAT3 target genes, MMP9 and TWIST.
We show that USP22 is a new regulator of the SIRT1-STAT3 signaling pathway and report a new mechanistic explanation for cross talk between USP22 and the SIRT1-STAT pathways.
背景/目的：泛素特异性蛋白酶USP22介导多种细胞和机体过程，如细胞生长、凋亡和肿瘤恶性进展。然而，调节USP22活性的分子机制仍知之甚少。在此，我们鉴定出信号转导和转录激活因子3（STAT3）是一种新的USP22相互作用蛋白。
我们使用蛋白质免疫印迹法和逆转录-聚合酶链反应（RT-PCR）来检测转染了表达质粒或特异性小干扰RNA（siRNA）的人胚肾293细胞（HEK293）和结肠癌细胞系中的关键蛋白、乙酰化STAT3和mRNA水平。免疫共沉淀用于证明蛋白质-蛋白质相互作用和蛋白质复合物组成。
USP22过表达通过去泛素化沉默调节蛋白1（SIRT1）下调STAT3乙酰化。发现这三种蛋白存在于单一蛋白质复合物中。siRNA介导的内源性USP22缺失导致SIRT1不稳定并提高STAT3乙酰化水平。与这一发现一致，USP22还下调了两个已知的STAT3靶基因基质金属蛋白酶9（MMP9）和 Twist 相关蛋白1（TWIST）的表达。
我们表明USP22是SIRT1-STAT3信号通路的新调节因子，并报道了USP22与SIRT1-STAT信号通路之间相互作用的新机制解释。
