Genovese Ilaria, Fiorillo Annarita, Ilari Andrea, Masciarelli Silvia, Fazi Francesco, Colotti Gianni
Department of Biochemical Sciences, Sapienza University, Rome, Italy.
IBPM-CNR Institute of Molecular Biology and Pathology, Italian National Research Council, Rome, Italy.
Cell Death Dis. 2017 Jul 20;8(7):e2950. doi: 10.1038/cddis.2017.342.
Sorcin is a calcium binding protein that plays an important role in multidrug resistance (MDR) in tumors, since its expression confers resistance to doxorubicin and to other chemotherapeutic drugs. In this study, we show that Sorcin is able to bind doxorubicin, vincristine, paclitaxel and cisplatin directly and with high affinity. The high affinity binding of doxorubicin to sorcin has been demonstrated with different techniques, that is, surface plasmon resonance, fluorescence titration and X-ray diffraction. Although the X-ray structure of sorcin in complex with doxorubicin has been solved at low resolution, it allows the identification of one of the two doxorubicin binding sites, placed at the interface between the EF5 loop the G helix and the EF4 loop. We show that Sorcin cellular localization changes upon doxorubicin treatment, an indication that the protein responds to doxorubicin and it presumably binds the drug also inside the cell, soon after drug entrance. We also demonstrate that Sorcin is able to limit the toxic effects of the chemotherapeutic agent in the cell. In addition, Sorcin silencing increases cell death upon treatment with doxorubicin, increases the accumulation of doxorubicin in cell nucleus, decreases the expression of MDR1 and doxorubicin efflux via MDR1.
索辛蛋白是一种钙结合蛋白，在肿瘤的多药耐药性（MDR）中发挥重要作用，因为其表达赋予对阿霉素和其他化疗药物的耐药性。在本研究中，我们表明索辛蛋白能够直接且以高亲和力结合阿霉素、长春新碱、紫杉醇和顺铂。阿霉素与索辛蛋白的高亲和力结合已通过不同技术得到证实，即表面等离子体共振、荧光滴定和X射线衍射。尽管索辛蛋白与阿霉素复合物的X射线结构已在低分辨率下解析，但它能确定两个阿霉素结合位点之一，该位点位于EF5环、G螺旋和EF4环之间的界面处。我们表明，阿霉素处理后索辛蛋白的细胞定位发生变化，这表明该蛋白对阿霉素有反应，并且在药物进入细胞后不久，它可能也在细胞内结合药物。我们还证明索辛蛋白能够限制化疗药物在细胞中的毒性作用。此外，索辛蛋白沉默会增加阿霉素处理后的细胞死亡，增加阿霉素在细胞核中的积累，降低MDR1的表达以及通过MDR1的阿霉素外排。
