School of Kinesiology and Health Science, Muscle Health Research Centre, York University , Toronto, Ontario , Canada.
Am J Physiol Cell Physiol. 2019 Mar 1;316(3):C449-C455. doi: 10.1152/ajpcell.00384.2018. Epub 2019 Jan 9.
Microtubule-targeting chemotherapies are linked to impaired cellular metabolism, which may contribute to skeletal muscle dysfunction. However, the mechanisms by which metabolic homeostasis is perturbed remains unknown. Tubulin, the fundamental unit of microtubules, has been implicated in the regulation of mitochondrial-cytosolic ADP/ATP exchange through its interaction with the outer membrane voltage-dependent anion channel (VDAC). Based on this model, we predicted that disrupting microtubule architecture with the stabilizer paclitaxel and destabilizer vinblastine would impair skeletal muscle mitochondrial bioenergetics. Here, we provide in vitro evidence of a direct interaction between both α-tubulin and βII-tubulin with VDAC2 in untreated single extensor digitorum longus (EDL) fibers. Paclitaxel increased both α- and βII-tubulin-VDAC2 interactions, whereas vinblastine had no effect. Utilizing a permeabilized muscle fiber bundle preparation that retains the cytoskeleton, paclitaxel treatment impaired the ability of ADP to attenuate HO emission, resulting in greater HO emission kinetics. Despite no effect on tubulin-VDAC2 binding, vinblastine still altered mitochondrial bioenergetics through a surprising increase in ADP-stimulated respiration while also impairing ADP suppression of HO and increasing mitochondrial susceptibility to calcium-induced formation of the proapoptotic permeability transition pore. Collectively, these results demonstrate that altering microtubule architecture with chemotherapeutics disrupts mitochondrial bioenergetics in EDL skeletal muscle. Specifically, microtubule stabilization increases HO emission by impairing ADP sensitivity in association with greater tubulin-VDAC binding. In contrast, decreasing microtubule abundance triggers a broad impairment of ADP's governance of respiration and HO emission as well as calcium retention capacity, albeit through an unknown mechanism.
微管靶向化疗与细胞代谢受损有关，这可能导致骨骼肌功能障碍。然而，代谢平衡受到干扰的机制尚不清楚。微管的基本单位微管蛋白已被牵连到通过与其外膜电压依赖性阴离子通道（VDAC）的相互作用调节线粒体-细胞质 ADP/ATP 交换。基于这个模型，我们预测用稳定剂紫杉醇和破坏剂长春碱破坏微管结构会损害骨骼肌线粒体生物能。在这里，我们提供了未经处理的单一伸肌（EDL）纤维中α-微管蛋白和βII-微管蛋白与 VDAC2 之间直接相互作用的体外证据。紫杉醇增加了α-和βII-微管蛋白与 VDAC2 的相互作用，而长春碱则没有影响。利用保留细胞骨架的通透性肌纤维束制剂，紫杉醇处理会损害 ADP 减弱 HO 发射的能力，导致更大的 HO 发射动力学。尽管紫杉醇对微管蛋白 VDAC2 结合没有影响，但长春碱仍然通过增加 ADP 刺激的呼吸作用改变了线粒体生物能，同时还损害了 ADP 对 HO 的抑制作用，并增加了线粒体对钙诱导形成促凋亡通透性转换孔的敏感性。总的来说，这些结果表明，用化疗药物改变微管结构会破坏 EDL 骨骼肌中的线粒体生物能。具体来说，微管稳定通过损害与更大的微管蛋白 VDAC 结合相关的 ADP 敏感性来增加 HO 发射。相比之下，减少微管数量会触发 ADP 对呼吸和 HO 发射以及钙保留能力的广泛治理受损，尽管其机制尚不清楚。
