Prosurvival Bcl-2 family members affect autophagy only indirectly, by inhibiting Bax and Bak
Prosurvival Bcl-2 family members affect autophagy only indirectly, by inhibiting Bax and Bak
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DOI：
10.1073/pnas.1406425111
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发表时间：
2014-06-10
影响因子：
11.1
通讯作者：
Vaux, David L.
中科院分区：
文献类型：
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作者：
Lindqvist, Lisa M.;Heinlein, Melanie;Vaux, David L.
抗凋亡 B 细胞淋巴瘤 2 (Bcl-2) 家族成员，如 Bcl-2、髓细胞白血病 1 (Mcl-1) 和 B 细胞淋巴瘤-X Large (Bcl-xL) 被认为通过直接结合 Beclin 1/Atg6 的 BH3 结构域来抑制自噬。然而，这些 Bcl-2 家族蛋白也会阻断 Bcl-2 相关 X (Bax) 和 Bcl-2 同源拮抗剂/杀伤剂 (Bak) 的促凋亡活性，并且许多自噬诱导剂也会导致细胞死亡。因此，当线粒体介导的细胞凋亡途径发挥作用时，此类实验的解释就很复杂。为了直接测试内源性抗凋亡 Bcl-2 家族成员在没有细胞凋亡的情况下对自噬的影响，我们在缺乏必需细胞死亡介质 Bax 和 Bak 的细胞中抑制了它们的活性。我们还使用诱导型慢病毒载体在细胞中过表达 Bcl-2、Bcl-xL 或 Mcl-1，并对它们进行促进自噬的治疗。在 Bax 和 Bak 缺失的情况下，Bcl-2、Bcl-xL 和 Mcl-1 对骨髓细胞或成纤维细胞系的自噬或细胞死亡没有可检测到的影响。另一方面，当 Bax 和 Bak 存在时，抑制促存活的 Bcl-2 家族成员会刺激自噬，但这与细胞死亡增加相关。此外，在缺乏 Bax 和 Bak 的情况下，氨基酸饥饿、依托泊苷或白细胞介素 3 撤除诱导的自噬抑制不会影响细胞死亡。这些结果表明，抗凋亡 Bcl-2 家族成员并不直接抑制自噬途径的组成部分，而是通过抑制 Bax 和 Bak 来间接影响自噬。
Antiapoptotic B-cell lymphoma 2 (Bcl-2) family members such as Bcl-2, myeloid cell leukemia 1 (Mcl-1), and B-cell lymphoma-X large (Bcl-xL) are proposed to inhibit autophagy by directly binding to the BH3 domain of Beclin 1/Atg6. However, these Bcl-2 family proteins also block the proapoptotic activity of Bcl-2-associated X (Bax) and Bcl-2 homologous antagonist/killer (Bak), and many inducers of autophagy also cause cell death. Therefore, when the mitochondrial-mediated apoptosis pathway is functional, interpretation of such experiments is complicated. To directly test the impact of the endogenous antiapoptotic Bcl-2 family members on autophagy in the absence of apoptosis, we inhibited their activity in cells lacking the essential cell death mediators Bax and Bak. We also used inducible lentiviral vectors to overexpress Bcl-2, Bcl-xL, or Mcl-1 in cells and subjected them to treatments that promote autophagy. In the absence of Bax and Bak, Bcl-2, Bcl-xL, and Mcl-1 had no detectable effect on autophagy or cell death in myeloid or fibroblast cell lines. On the other hand, when Bax and Bak were present, inhibiting the prosurvival Bcl-2 family members stimulated autophagy, but this correlated with increased cell death. In addition, inhibition of autophagy induced by amino acid starvation, etoposide, or interleukin-3 withdrawal did not affect cell death in the absence of Bax and Bak. These results demonstrate that the antiapoptotic Bcl-2 family members do not directly inhibit components of the autophagic pathway but instead affect autophagy indirectly, owing to their inhibition of Bax and Bak.