The canonical function of Bcl-2 family proteins is to regulate mitochondrial membrane integrity. In response to apoptotic signals the multi-domain pro-apoptotic proteins Bax and Bak are activated and perforate the mitochondrial outer membrane by a mechanism which is inhibited by their interaction with pro-survival members of the family. However, other studies have shown that Bax and Bak may have additional, non-canonical functions, which include stress-induced nuclear envelope rupture and discharge of nuclear proteins into the cytosol. We show here that the apoptotic stimuli cisplatin and staurosporine induce a Bax/Bak-dependent degradation and subcellular redistribution of nesprin-1 and nesprin-2 but not nesprin-3, of the linker of nucleoskeleton and cytoskeleton (LINC) complex. The degradation and redistribution were caspase-independent and did not occur in Bax/Bak double knockout (DKO) mouse embryo fibroblasts (MEFs). Re-expression of Bax in Bax/Bak DKO MEFs restored stress-induced redistribution of nesprin-2 by a mechanism which requires Bax membrane localization and integrity of the α helices 5/6, and the Bcl-2 homology 3 (BH3) domain. We found that nesprin-2 interacts with Bax in close proximity to perinuclear mitochondria in mouse and human cells. This interaction requires the mitochondrial targeting and N-terminal region but not the BH3 domain of Bax. Our results identify nesprin-2 as a Bax binding partner and also a new function of Bax in impairing the integrity of the LINC complex.

Bcl-2 家族蛋白的典型功能是调节线粒体膜的完整性。响应细胞凋亡信号，多结构域促细胞凋亡蛋白 Bax 和 Bak 被激活，并通过一种机制穿孔线粒体外膜，而该机制因其与家族促存活成员的相互作用而受到抑制。然而，其他研究表明 Bax 和 Bak 可能具有额外的非规范功能，其中包括应激诱导的核膜破裂和将核蛋白释放到细胞质中。我们在此表明​​，细胞凋亡刺激顺铂和星形孢菌素诱导核骨架和细胞骨架（LINC）复合物连接体的 Nesprin-1 和 Nesprin-2（而非 Nesprin-3）的 Bax/Bak 依赖性降解和亚细胞重新分布。降解和重新分布不依赖于半胱天冬酶，并且在 Bax/Bak 双敲除 (DKO) 小鼠胚胎成纤维细胞 (MEF) 中不会发生。 Bax/Bak DKO MEF 中 Bax 的重新表达通过需要 Bax 膜定位和 α 螺旋 5/6 和 Bcl-2 同源 3 (BH3) 结构域完整性的机制恢复了应激诱导的 nesprin-2 重新分布。我们发现，在小鼠和人类细胞中，nesprin-2 与靠近核周线粒体的 Bax 相互作用。这种相互作用需要线粒体靶向和 N 末端区域，但不需要 Bax 的 BH3 结构域。我们的结果确定 nesprin-2 是 Bax 结合伴侣，也是 Bax 损害 LINC 复合物完整性的新功能。