Li Lei, Yao Ya-Chao, Gu Xiao-Qiong, Che Di, Ma Cai-Qi, Dai Zhi-Yu, Li Cen, Zhou Ti, Cai Wei-Bin, Yang Zhong-Han, Yang Xia, Gao Guo-Quan
From the Department of Biochemistry, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, the Department of Reproductive Medicine Center, Key Laboratory for Reproductive Medicine of Guangdong Province, Third Affiliated Hospital of Guangzhou Medical University, 63 Duobao Road, Guangzhou 510150.
the Laboratory Center of Guangdong NO.2 Provincial People's Hospital, Guangzhou 510317.
J Biol Chem. 2014 Nov 21;289(47):32628-38. doi: 10.1074/jbc.M114.567792. Epub 2014 Oct 8.
Human plasminogen kringle 5 (K5) is known to display its potent anti-angiogenesis effect through inducing endothelial cell (EC) apoptosis, and the voltage-dependent anion channel 1 (VDAC1) has been identified as a receptor of K5. However, the exact role and underlying mechanisms of VDAC1 in K5-induced EC apoptosis remain elusive. In the current study, we showed that K5 increased the protein level of VDAC1, which initiated the mitochondrial apoptosis pathway of ECs. Our findings also showed that K5 inhibited the ubiquitin-dependent degradation of VDAC1 by promoting the phosphorylation of VDAC1, possibly at Ser-12 and Thr-107. The phosphorylated VDAC1 was attenuated by the AKT agonist, glycogen synthase kinase (GSK) 3β inhibitor, and siRNA, suggesting that K5 increased VDAC1 phosphorylation via the AKT-GSK3β pathway. Furthermore, K5 promoted cell surface translocation of VDAC1, and binding between K5 and VDAC1 was observed on the plasma membrane. HKI protein blocked the impact of K5 on the AKT-GSK3β pathway by competitively inhibiting the interaction of K5 and cell surface VDAC1. Moreover, K5-induced EC apoptosis was suppressed by VDAC1 antibody. These data show for the first time that K5-induced EC apoptosis is mediated by the positive feedback loop of "VDAC1-AKT-GSK3β-VDAC1," which may provide new perspectives on the mechanisms of K5-induced apoptosis.
已知人纤溶酶原kringle 5(K5)通过诱导内皮细胞(EC)凋亡发挥其强大的抗血管生成作用,并且电压依赖性阴离子通道1(VDAC1)已被确定为K5的受体。然而,VDAC1在K5诱导的EC凋亡中的确切作用和潜在机制仍不清楚。在本研究中,我们发现K5增加了VDAC1的蛋白水平,从而启动了EC的线粒体凋亡途径。我们的研究结果还表明,K5通过促进VDAC1的磷酸化(可能是在Ser-12和Thr-107位点)来抑制VDAC1的泛素依赖性降解。磷酸化的VDAC1被AKT激动剂、糖原合酶激酶(GSK)3β抑制剂和小干扰RNA(siRNA)减弱,这表明K5通过AKT-GSK3β途径增加VDAC1的磷酸化。此外,K5促进了VDAC1向细胞表面的转运,并且在质膜上观察到K5与VDAC1之间的结合。HKI蛋白通过竞争性抑制K5与细胞表面VDAC1的相互作用,阻断了K5对AKT-GSK3β途径的影响。此外,VDAC1抗体抑制了K5诱导的EC凋亡。这些数据首次表明,K5诱导的EC凋亡是由“VDAC1-AKT-GSK3β-VDAC1”正反馈环介导的,这可能为K5诱导凋亡的机制提供新的视角。