Lin Chiou-Feng, Tsai Cheng-Chieh, Huang Wei-Ching, Wang Yu-Chih, Tseng Po-Chun, Tsai Tsung-Ting, Chen Chia-Ling
Department of Microbiology and Immunology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, 110, Taiwan.
Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, 110, Taiwan.
PLoS One. 2016 Jan 4;11(1):e0145460. doi: 10.1371/journal.pone.0145460. eCollection 2016.
Glycogen synthase kinase-3β (GSK-3β) regulates the sequential activation of caspase-2 and caspase-8 before mitochondrial apoptosis. Here, we report the regulation of Mcl-1 destabilization and cathepsin D-regulated caspase-8 activation by GSK-3β and caspase-2. Treatment with either the ceramide analogue C2-ceramide or the topoisomerase II inhibitor etoposide sequentially induced lysosomal membrane permeabilization (LMP), the reduction of mitochondrial transmembrane potential, and apoptosis. Following LMP, cathepsin D translocated from lysosomes to the cytoplasm, whereas inhibiting cathepsin D blocked mitochondrial apoptosis. Furthermore, cathepsin D caused the activation of caspase-8 but not caspase-2. Inhibiting GSK-3β and caspase-2 blocked Mcl-1 destabilization, LMP, cathepsin D re-localization, caspase-8 activation, and mitochondrial apoptosis. Expression of Mcl-1 was localized to the lysosomes, and forced expression of Mcl-1 prevented apoptotic signaling via the lysosomal-mitochondrial pathway. These results demonstrate the importance of GSK-3β and caspase-2 in ceramide- and etoposide-induced apoptosis through mechanisms involving Mcl-1 destabilization and the lysosomal-mitochondrial axis.
糖原合酶激酶-3β（GSK-3β）在线粒体凋亡之前调节半胱天冬酶-2和半胱天冬酶-8的顺序激活。在此，我们报告了GSK-3β和半胱天冬酶-2对Mcl-1稳定性破坏和组织蛋白酶D调节的半胱天冬酶-8激活的调控作用。用神经酰胺类似物C2-神经酰胺或拓扑异构酶II抑制剂依托泊苷处理会依次诱导溶酶体膜通透性增加（LMP）、线粒体跨膜电位降低和细胞凋亡。LMP发生后，组织蛋白酶D从溶酶体转移至细胞质，而抑制组织蛋白酶D可阻断线粒体凋亡。此外，组织蛋白酶D可导致半胱天冬酶-8激活，但不会导致半胱天冬酶-2激活。抑制GSK-3β和半胱天冬酶-2可阻断Mcl-1稳定性破坏、LMP、组织蛋白酶D重新定位、半胱天冬酶-8激活以及线粒体凋亡。Mcl-1的表达定位于溶酶体，强制表达Mcl-1可通过溶酶体-线粒体途径阻止凋亡信号传导。这些结果证明了GSK-3β和半胱天冬酶-2在神经酰胺和依托泊苷诱导的细胞凋亡中的重要性，其作用机制涉及Mcl-1稳定性破坏和溶酶体-线粒体轴。
