Department of Molecular Biology and Immunology and Institute for Cancer Research, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA.
Biochemistry. 2010 Mar 16;49(10):2216-26. doi: 10.1021/bi9013038.
Annexin A2 (AnxA2) is a multifunctional Ca(2+)-dependent phospholipid-binding protein, and its overexpression is implicated in malignant transformation of several cancers. In prostate cancer, however, the expression of AnxA2 is lost in prostate intraepithelial neoplasia and reappears in the high-grade tumors, suggesting a complex regulation of AnxA2 in the prostate microenvironment. Since a majority of the biological functions of AnxA2 are mediated by its interaction with other proteins, we performed a yeast two-hybrid assay to search for novel interactors of AnxA2. Our studies revealed that signal transducer and activator of transcription 6 (STAT6), a member of the STAT family of transcription factors, is a binding partner of AnxA2. We confirmed AnxA2-STAT6 interaction by in vitro co-immunoprecipitation and fluorescence resonance energy transfer (FRET) studies and demonstrated that AnxA2 interacts with phosphorylated STAT6. Furthermore, chromatin immunoprecipitation (ChIP) assay revealed that AnxA2 is associated with the STAT6 DNA-binding complex, and luciferase reporter assays demonstrated that AnxA2 upregulates the activity of STAT6. Upon interleukin-4 treatment, AnxA2 stabilizes the cytosolic levels of phosphorylated STAT6 and promotes its nuclear entry. These findings suggest that AnxA2-STAT6 interactions could have potential implications in prostate cancer progression. This report is the first to demonstrate the interaction of AnxA2 with STAT6 and suggests a possible mechanism by which AnxA2 contributes to the metastatic processes of prostate cancer.
膜联蛋白 A2（AnxA2）是一种多功能的 Ca2+ 依赖性磷脂结合蛋白，其过表达与几种癌症的恶性转化有关。然而，在前列腺癌中，AnxA2 的表达在前列腺上皮内瘤变中丢失，而在高级别肿瘤中重新出现，这表明 AnxA2 在前列腺微环境中的表达受到复杂的调控。由于 AnxA2 的大多数生物学功能都是通过与其他蛋白质的相互作用来介导的，因此我们进行了酵母双杂交实验来寻找 AnxA2 的新相互作用蛋白。我们的研究表明，信号转导和转录激活因子 6（STAT6）是转录因子 STAT 家族的成员，是 AnxA2 的结合伴侣。我们通过体外共免疫沉淀和荧光共振能量转移（FRET）研究证实了 AnxA2-STAT6 相互作用，并证明 AnxA2 与磷酸化的 STAT6 相互作用。此外，染色质免疫沉淀（ChIP）实验表明 AnxA2 与 STAT6 的 DNA 结合复合物相关联，而荧光素酶报告基因实验表明 AnxA2 可上调 STAT6 的活性。在白细胞介素-4 处理后，AnxA2 稳定了细胞质中磷酸化 STAT6 的水平并促进其核内进入。这些发现表明 AnxA2-STAT6 相互作用可能对前列腺癌的进展有潜在的影响。本报告首次证明了 AnxA2 与 STAT6 的相互作用，并提出了 AnxA2 促进前列腺癌转移过程的可能机制。
