Département de kinésiologie, Université de Montréal, C.P. 6128, Succursalle Centre-Ville, Montréal, Québec, Canada H3C 3J7.
J Physiol. 2011 Feb 15;589(Pt 4):855-61. doi: 10.1113/jphysiol.2010.202036. Epub 2011 Jan 4.
In the present study, we specifically determined whether the regulatory protein cyclophilin-D (CypD), and by extension opening of the permeability transition pore (PTP), is involved in the activation of mitochondria-derived apoptotic signalling previously described in skeletal muscle following loss of innervation. For this purpose, CypD-defficient (CypD-KO) mice and their littermate controls were submitted to unilateral sciatic nerve transection, and mitochondrial resistance to Ca2+-induced opening of the PTP, and muscle apoptotic signalling were investigated 14 days post-surgery. Denervation caused atrophy, facilitated Ca2+-induced opening of the PTP in vitro in permeabilized muscle fibres, and activation of the apoptotic proteolytic cascade in the whole muscle of both mouse strains. In CypD-KO mice, mitochondrial resistance to Ca2+-induced PTP opening was greater than in WT mice, in both the normal and the denervated state, indicating that lack of CypD desensitized to PTP opening. However, denervation in CypD-KO mice still resulted in a facilitation of PTP opening compared to normally innervated contralateral muscle, indicating that in vitro additional factors could poise mitochondria from denervated muscle toward PTP opening. At the whole muscle level, lack of CypD, despite conferring greater resistance to PTP opening, did not protect against atrophy, release of mitochondrial pro-apoptotic factors and activation of caspases following denervation. Altogether, these results provide direct evidence that CypD-dependent PTP opening is dispensable for atrophy and apoptotic signalling in skeletal muscle following denervation.
在本研究中，我们特别确定调节蛋白亲环素 D（CypD），以及由此延伸的通透性转换孔（PTP）的开放，是否参与了先前在失神经支配的骨骼肌中描述的线粒体源性凋亡信号的激活。为此，我们对 CypD 缺陷型（CypD-KO）小鼠及其同窝对照进行了单侧坐骨神经切断术，并在手术后 14 天研究了线粒体对 Ca2+诱导的 PTP 开放的抗性和肌肉凋亡信号。失神经支配导致肌肉萎缩，促进了体外去神经支配的肌纤维中 Ca2+诱导的 PTP 开放，并激活了两种小鼠品系的整个肌肉中的凋亡蛋白酶级联反应。在 CypD-KO 小鼠中，线粒体对 Ca2+诱导的 PTP 开放的抗性大于 WT 小鼠，无论是在正常还是失神经支配状态下，表明缺乏 CypD 使 PTP 开放脱敏。然而，与正常神经支配的对侧肌肉相比，CypD-KO 小鼠中的失神经支配仍然导致 PTP 开放的促进，表明在体外，来自失神经支配的肌肉的其他因素可以使 PTP 更容易打开。在整个肌肉水平上，尽管 CypD 的缺乏赋予了对 PTP 开放更大的抗性，但不能防止失神经支配后的萎缩、线粒体促凋亡因子的释放和 caspase 的激活。总之，这些结果提供了直接证据，表明 CypD 依赖性 PTP 开放对于失神经支配后的骨骼肌萎缩和凋亡信号是可有可无的。
