Nader Moni, Khalil Bariaa, Kattuah Wejdan, Dzimiri Nduna, Bakheet Dana
Department of Physiological Sciences, College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia.
Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
Heliyon. 2020 Sep 19;6(9):e04990. doi: 10.1016/j.heliyon.2020.e04990. eCollection 2020 Sep.
Striatin (STRN) is a multivalent protein holding great therapeutic potentials in view of its interaction with dynamic partners implicated in apoptosis. Although striatin-3 and striatin-4, that share high structural similarities with STRN, have been linked to apoptosis, the dynamics of STRN in apoptotic cells remain unclear. Herein, we report that the amount of STRN (110 kDa) is reduced in apoptotic cells, in response to various chemotherapeutic agents, thereby yielding a major polypeptide fragment at ~65 kDa, and three minor products at lower molecular weights. While STRN siRNA reduced the 65 kDa derivative fragment, the overexpression of a Myc-tagged STRN precipitated a novel fragment that was detected slightly higher than 65 kDa (due to the Myc-DDK tag on the cleaved fragment), confirming the cleavage of STRN during apoptosis. Interestingly, STRN cleavage was abrogated by the general caspase inhibitor Z-VAD.fmk. Cell fractionation revealed that the STRN pool, mainly distributed in the non-cytosolic fragment of naïve cells, translocates to the cytosol where it is proteolytically cleaved during apoptosis. Interestingly, the ectopic expression of caspase 3 in MCF-7 cells (deprived of caspase 3) induced STRN cleavage under apoptotic conditions. Inhibition of caspase 3 (Ac-DEVD-CHO) conferred a dose-dependent protection against the proteolytic cleavage of STRN. Collectively, our data provide cogent proofs that STRN translocates to the cytosol where it undergoes proteolytic cleavage in a caspase 3-dependent manner during apoptosis. Thus, this study projects the cleavage of STRN as a novel marker for apoptosis to serve pharmacological strategies targeting this particular form of cell death.
条纹蛋白（STRN）是一种多价蛋白，鉴于其与参与细胞凋亡的动态伙伴相互作用，具有巨大的治疗潜力。尽管与STRN具有高度结构相似性的条纹蛋白-3和条纹蛋白-4已与细胞凋亡相关联，但STRN在凋亡细胞中的动态变化仍不清楚。在此，我们报告，响应各种化疗药物，凋亡细胞中STRN（110 kDa）的量减少，从而产生一个约65 kDa的主要多肽片段和三个较低分子量的次要产物。虽然STRN siRNA减少了65 kDa的衍生片段，但Myc标签的STRN过表达沉淀出一个新片段，该片段的检测分子量略高于65 kDa（由于切割片段上的Myc-DDK标签），证实了凋亡过程中STRN的切割。有趣的是，通用的半胱天冬酶抑制剂Z-VAD.fmk消除了STRN的切割。细胞分级分离显示，STRN池主要分布在未成熟细胞的非胞质片段中，在凋亡过程中易位到胞质溶胶，在那里它被蛋白水解切割。有趣的是，MCF-7细胞（缺乏半胱天冬酶3）中半胱天冬酶3的异位表达在凋亡条件下诱导了STRN的切割。半胱天冬酶3的抑制（Ac-DEVD-CHO）对STRN的蛋白水解切割提供了剂量依赖性保护。总的来说，我们的数据提供了有力的证据，表明STRN易位到胞质溶胶，在凋亡过程中它以半胱天冬酶3依赖性方式经历蛋白水解切割。因此，本研究将STRN的切割作为细胞凋亡的一种新标记，以服务于针对这种特定形式细胞死亡的药理学策略。
