Cabrera Elisa, Raninga Prahlad, Khanna Kum Kum, Freire Raimundo
Unidad de Investigación, Hospital Universitario de Canarias, Ofra s/n, La Cuesta, 38320 La Laguna, Tenerife, Spain.
Instituto de Tecnologías Biomédicas, Universidad de La Laguna, 38200 San Cristóbal de La Laguna, Tenerife, Spain.
Cancers (Basel). 2019 Jul 29;11(8):1073. doi: 10.3390/cancers11081073.
Claspin is essential for activating the DNA damage checkpoint effector kinase Chk1, a target in oncotherapy. Claspin functions are tightly correlated to Claspin protein stability, regulated by ubiquitin-dependent proteasomal degradation. Here we identify Glycogen Synthase Kinase 3-β (GSK3-β) as a new regulator of Claspin stability. Interestingly, as Chk1, GSK3-β is a therapeutic target in cancer. GSK3-β inhibition or knockdown stabilizes Claspin, whereas a GSK3-β constitutively active form reduces Claspin protein levels by ubiquitination and proteasome-mediated degradation. Our results also suggest that GSK3-β modulates the interaction of Claspin with β-TrCP, a critical E3 ubiquitin ligase that regulates Claspin stability. Importantly, GSK3-β knock down increases Chk1 activation in response to DNA damage in a Claspin-dependent manner. Therefore, Chk1 activation could be a pro-survival mechanism that becomes activated upon GSK3-β inhibition. Importantly, treating triple negative breast cancer cell lines with Chk1 or GSK3-β inhibitors alone or in combination, demonstrates that Chk1/GSK3-β double inhibition restrains cell growth and triggers more apoptosis compared to individual treatments, thereby revealing novel possibilities for a combination therapy for cancer.
Claspin对于激活DNA损伤检查点效应激酶Chk1至关重要，Chk1是肿瘤治疗的一个靶点。Claspin的功能与Claspin蛋白稳定性密切相关，其稳定性受泛素依赖性蛋白酶体降解的调控。在此，我们鉴定出糖原合酶激酶3-β（GSK3-β）是Claspin稳定性的一种新调节因子。有趣的是，与Chk1一样，GSK3-β也是癌症治疗的一个靶点。抑制或敲低GSK3-β可使Claspin稳定，而持续激活的GSK3-β形式则通过泛素化和蛋白酶体介导的降解降低Claspin蛋白水平。我们的结果还表明，GSK3-β调节Claspin与β-TrCP的相互作用，β-TrCP是一种调节Claspin稳定性的关键E3泛素连接酶。重要的是，敲低GSK3-β以Claspin依赖的方式增加了DNA损伤时Chk1的激活。因此，Chk1激活可能是一种在GSK3-β受到抑制时被激活的促生存机制。重要的是，单独或联合使用Chk1或GSK3-β抑制剂处理三阴性乳腺癌细胞系，结果表明与单独治疗相比，Chk1/GSK3-β双重抑制可抑制细胞生长并引发更多凋亡，从而揭示了癌症联合治疗的新可能性。
