Vyas Sheela, Béchade Catherine, Riveau Béatrice, Downward Julian, Triller Antoine
INSERM U497, 46 rue d'Ulm, Paris 75005, France.
Hum Mol Genet. 2002 Oct 15;11(22):2751-64. doi: 10.1093/hmg/11.22.2751.
Infantile spinal muscular atrophy (SMA) is caused by mutations in the survival motor neuron (SMN)1 gene. We investigated the role of human (h) SMN protein on cell death in PC12 and Rat-1 cells. hSMN prolonged cell survival in PC12 cells deprived of trophic support and in Rat-1 cells induced to die by activation of the proto-oncogene c-Myc, to similar magnitude as Bcl-2 or IAP-2. While hSMN was ineffective in inhibiting apoptosis induced by ultraviolet light (UV) or etoposide treatment in proliferating PC12 or Rat-1 cells, a protective effect was observed in terminally NGF/dBcAMP-differentiated PC12 cells. hSMN inhibited the onset of apoptosis in NGF/dBcAMP-deprived or UV-treated co-differentiated PC12 cells by preventing cytochrome c release and caspase-3 activation, indicating that its effects are through suppression of the mitochondrial apoptotic pathway. Expressing hSMN deleted for exon 7 (Delta7) or for exons 6 and 7 (Delta6/7), or with the SMA point mutant Y272C, resulted in loss of survival function. Moreover, these mutants also exhibited pro-apoptotic effects in Rat-1 cells. The localization pattern of full-length hSMN in PC12 and Rat-1 cells was similar to that of endogenous SMN: granular labelling in the cytoplasm and discrete fluorescence spots in the nucleus, some of which co-localized with p80 coilin, the characteristic marker of Cajal bodies. However, cytoplasmic and nuclear aggregates were often seen with hSMNDelta7, whereas the hSMNDelta6/7 mutant showed homogenous nuclear labelling that excluded the nucleolus. Thus, our results show that the C-terminal region is critical in suppression of apoptosis by SMN.
婴儿脊髓性肌萎缩症（SMA）由存活运动神经元（SMN）1基因的突变引起。我们研究了人（h）SMN蛋白在PC12细胞和大鼠-1细胞死亡中的作用。hSMN可延长缺乏营养支持的PC12细胞以及通过原癌基因c-Myc激活诱导死亡的大鼠-1细胞的存活时间，其程度与Bcl-2或IAP-2相似。虽然hSMN在抑制增殖的PC12或大鼠-1细胞中紫外线（UV）或依托泊苷处理诱导的凋亡方面无效，但在终末NGF/dBcAMP分化的PC12细胞中观察到了保护作用。hSMN通过阻止细胞色素c释放和半胱天冬酶-3激活，抑制了NGF/dBcAMP剥夺或UV处理的共分化PC12细胞中凋亡的发生，表明其作用是通过抑制线粒体凋亡途径实现的。表达缺失外显子7（Delta7）或外显子6和7（Delta6/7）的hSMN，或带有SMA点突变Y272C的hSMN，导致存活功能丧失。此外，这些突变体在大鼠-1细胞中还表现出促凋亡作用。全长hSMN在PC12和大鼠-1细胞中的定位模式与内源性SMN相似：细胞质中的颗粒状标记和细胞核中的离散荧光斑点，其中一些与Cajal体的特征性标记p80卷曲蛋白共定位。然而，hSMNDelta7常可见细胞质和细胞核聚集物，而hSMNDelta6/7突变体显示均匀的核标记，排除了核仁。因此，我们的结果表明C末端区域在SMN抑制凋亡中起关键作用。
