Hsp70 inhibits heat-induced apoptosis upstream of mitochondria by preventing Bax translocation
Hsp70 inhibits heat-induced apoptosis upstream of mitochondria by preventing Bax translocation
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DOI：
10.1074/jbc.m509497200
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发表时间：
2005-11-18
影响因子：
4.8
通讯作者：
Mosser, DD
中科院分区：
文献类型：
--
作者：
Stankiewicz, AR;Lachapelle, G;Mosser, DD
Hsp 70过表达可保护细胞免受应激诱导的凋亡。我们以前的观察，热休克蛋白70抑制细胞色素c的释放在热应激细胞导致我们检查事件发生的上游线粒体破坏。在这项研究中，我们研究了热休克对促凋亡Bcl-2家族成员Bax的影响，因为它在调节应激细胞中细胞色素c释放方面发挥着核心作用。我们发现，热休克引起Bax的构象变化，导致其易位到线粒体，稳定的膜协会，和寡聚化。所有这些事件在具有升高的Hsp 70水平的细胞中被抑制。在对照或热休克细胞中，Hsp 70没有与Bax发生物理相互作用，表明Hsp 70的作用是抑制导致Bax激活的信号。热休克蛋白70抑制应激诱导的JNK激活和抑制JNK与SP 600125或表达的显性负突变体的JNK阻断Bax易位有效热休克蛋白70过表达。热休克蛋白70没有保护细胞表达的突变形式的Bax，具有组成性膜插入能力或细胞处理的小分子激活剂的线粒体形成，这表明它是不能防止细胞死亡后，线粒体破坏和半胱天冬酶激活已经发生。这些结果表明，热休克蛋白70阻断热诱导的细胞凋亡，主要是通过抑制Bax的激活，从而防止释放的促凋亡因子从线粒体。因此，热休克蛋白70，抑制事件导致线粒体膜透化在热应激细胞，从而控制死亡的决定，但不干扰细胞死亡后，这一事件已经发生。
Hsp70 overexpression can protect cells from stress-induced apoptosis. Our previous observation that Hsp70 inhibits cytochrome c release in heat-stressed cells led us to examine events occurring upstream of mitochondrial disruption. In this study we examined the effects of heat shock on the proapoptotic Bcl-2 family member Bax because of its central role in regulating cytochrome c release in stressed cells. We found that heat shock caused a conformational change in Bax that leads to its translocation to mitochondria, stable membrane association, and oligomerization. All of these events were inhibited in cells that had elevated levels of Hsp70. Hsp70 did not physically interact with Bax in control or heat-shocked cells, indicating that Hsp70 acts to suppress signals leading to Bax activation. Hsp70 inhibited stress-induced JNK activation and inhibition of JNK with SP600125 or by expression of a dominant negative mutant of JNK-blocked Bax translocation as effectively as Hsp70 overexpression. Hsp70 did not protect cells expressing a mutant form of Bax that has constitutive membrane insertion capability or cells treated with a small molecule activator of apoptosome formation, indicating that it is unable to prevent cell death after mitochondrial disruption and caspase activation have occurred. These results indicate that Hsp70 blocks heat-induced apoptosis primarily by inhibiting Bax activation and thereby preventing the release of proapoptotic factors from mitochondria. Hsp70, therefore, inhibits events leading up to mitochondrial membrane permeabilization in heat-stressed cells and thereby controls the decision to die but does not interfere with cell death after this event has occurred.