Center for Cell Death, Injury & Regeneration, Department of Pharmaceutical & Biomedical Sciences, Medical University of South Carolina, Charleston, South Carolina, USA.
Cancer Res. 2010 Dec 15;70(24):10192-201. doi: 10.1158/0008-5472.CAN-10-2429.
Formation of the mitochondrial membrane potential (ΔΨ) depends on flux of respiratory substrates, ATP, ADP, and Pi through voltage-dependent anion channels (VDAC). As tubulin promotes single-channel closure of VDAC, we hypothesized that tubulin is a dynamic regulator of ΔΨ, which in cultured cancer cells was assessed by confocal microscopy of the potential-indicating fluorophore tetramethylrhodamine methylester (TMRM). Microtubule destabilizers, rotenone, colchicine, and nocodazole, and the microtubule stabilizer paclitaxel increased and decreased cellular free tubulin, respectively, and in parallel decreased and increased ΔΨ. Protein kinase A (PKA) activation by cAMP analogues and glycogen synthase kinase 3β (GSK-3β) inhibition decreased ΔΨ, whereas PKA inhibition hyperpolarized, consistent with reports that PKA and GSK-3β decrease and increase VDAC conductance, respectively. Plasma membrane potential assessed by DiBAC(4)(3) was not altered by any of the treatments. We propose that inhibition of VDAC by free tubulin limits mitochondrial metabolism in cancer cells.
线粒体膜电位（ΔΨ）的形成取决于呼吸底物、ATP、ADP 和 Pi 通过电压依赖性阴离子通道（VDAC）的流量。由于微管蛋白促进 VDAC 的单通道关闭，我们假设微管蛋白是 ΔΨ 的动态调节剂，在培养的癌细胞中通过四甲基罗丹明甲酯（TMRM）荧光探针的共聚焦显微镜评估。微管不稳定剂鱼藤酮、秋水仙碱和诺考达唑和微管稳定剂紫杉醇分别增加和减少细胞游离微管蛋白，并平行地降低和增加 ΔΨ。cAMP 类似物激活蛋白激酶 A（PKA）和糖原合酶激酶 3β（GSK-3β）抑制降低 ΔΨ，而 PKA 抑制则使膜超极化，这与 PKA 和 GSK-3β 分别降低和增加 VDAC 电导的报道一致。用 DiBAC（4）（3）评估的质膜电位不受任何处理的影响。我们提出，游离微管蛋白对 VDAC 的抑制限制了癌细胞中的线粒体代谢。
