Radhakrishnan Vijayababu M, Kojs Pawel, Young Gavin, Ramalingam Rajalakshmy, Jagadish Bhumasamudram, Mash Eugene A, Martinez Jesse D, Ghishan Fayez K, Kiela Pawel R
Department of Pediatrics, Steele Children's Research Center, University of Arizona Health Sciences Center, Tucson, Arizona, United States of America.
Department of Nutritional Sciences, Tucson, Arizona, United States of America.
PLoS One. 2014 Jan 22;9(1):e85796. doi: 10.1371/journal.pone.0085796. eCollection 2014.
Cortactin (CTTN), first identified as a major substrate of the Src tyrosine kinase, actively participates in branching F-actin assembly and in cell motility and invasion. CTTN gene is amplified and its protein is overexpressed in several types of cancer. The phosphorylated form of cortactin (pTyr(421)) is required for cancer cell motility and invasion. In this study, we demonstrate that a majority of the tested primary colorectal tumor specimens show greatly enhanced expression of pTyr(421)-CTTN, but no change at the mRNA level as compared to healthy subjects, thus suggesting post-translational activation rather than gene amplification in these tumors. Curcumin (diferulolylmethane), a natural compound with promising chemopreventive and chemosensitizing effects, reduced the indirect association of cortactin with the plasma membrane protein fraction in colon adenocarcinoma cells as measured by surface biotinylation, mass spectrometry, and Western blotting. Curcumin significantly decreased the pTyr(421)-CTTN in HCT116 cells and SW480 cells, but was ineffective in HT-29 cells. Curcumin physically interacted with PTPN1 tyrosine phosphatases to increase its activity and lead to dephosphorylation of pTyr(421)-CTTN. PTPN1 inhibition eliminated the effects of curcumin on pTyr(421)-CTTN. Transduction with adenovirally-encoded CTTN increased migration of HCT116, SW480, and HT-29. Curcumin decreased migration of HCT116 and SW480 cells which highly express PTPN1, but not of HT-29 cells with significantly reduced endogenous expression of PTPN1. Curcumin significantly reduced the physical interaction of CTTN and pTyr(421)-CTTN with p120 catenin (CTNND1). Collectively, these data suggest that curcumin is an activator of PTPN1 and can reduce cell motility in colon cancer via dephosphorylation of pTyr(421)-CTTN which could be exploited for novel therapeutic approaches in colon cancer therapy based on tumor pTyr(421)-CTTN expression.
皮层肌动蛋白（CTTN）最初被鉴定为Src酪氨酸激酶的主要底物，它积极参与F-肌动蛋白分支组装以及细胞运动和侵袭过程。CTTN基因在几种癌症类型中发生扩增，其蛋白过表达。皮层肌动蛋白的磷酸化形式（pTyr(421)）对于癌细胞的运动和侵袭是必需的。在本研究中，我们证明，与健康受试者相比，大多数测试的原发性结直肠癌标本显示pTyr(421)-CTTN的表达大幅增强，但mRNA水平没有变化，因此表明这些肿瘤中存在翻译后激活而非基因扩增。姜黄素（二阿魏酰甲烷）是一种具有良好化学预防和化学增敏作用的天然化合物，通过表面生物素化、质谱分析和蛋白质印迹法检测发现，它减少了结肠腺癌细胞中皮层肌动蛋白与质膜蛋白组分的间接结合。姜黄素显著降低了HCT116细胞和SW480细胞中pTyr(421)-CTTN的水平，但对HT-29细胞无效。姜黄素与蛋白酪氨酸磷酸酶1（PTPN1）发生物理相互作用以增加其活性，并导致pTyr(421)-CTTN去磷酸化。抑制PTPN1消除了姜黄素对pTyr(421)-CTTN的影响。用腺病毒编码的CTTN进行转导增加了HCT116、SW480和HT-29细胞的迁移能力。姜黄素降低了高表达PTPN1的HCT116和SW480细胞的迁移能力，但对PTPN1内源性表达显著降低的HT-29细胞没有影响。姜黄素显著减少了CTTN和pTyr(421)-CTTN与p120连环蛋白（CTNND1）的物理相互作用。总体而言，这些数据表明姜黄素是PTPN1的激活剂，可通过使pTyr(421)-CTTN去磷酸化来降低结肠癌细胞的运动能力，这可为基于肿瘤pTyr(421)-CTTN表达的结肠癌治疗新方法提供依据。
