The chaperone heat shock protein 70 (Hsp70) is crucial for avoiding protein misfolding under stress, but is also up-regulated in many kinds of cancers, where its ability to buffer cellular stress prevents apoptosis. Previous research has suggested Hsp70 interacts with pro-apoptotic Bcl-2 family proteins, including Bim and Bax. However, a definitive demonstration of this interaction awaits, and insights into the structural basis and molecular mechanism remain unclear. Earlier studies have identified a Bcl-2 homology 3 (BH3) domain present in Bcl-2 family members that engages receptors to stimulate apoptosis. We now show that Hsp70 physically interacts with pro-apoptotic multidomain and BH3-only proteins via a BH3 domain, thereby serving as a novel BH3 receptor, using in vitro fluorescent polarization (FP), isothermal titration calorimetry (ITC), and cell-based co-immunoprecipitation (co-IP) experiments, 1H-15N-transverse relaxation optimized spectroscopy (TROSY-HSQC), trypsin proteolysis, ATPase activity, and denatured rhodanese aggregation measurements further demonstrated that BimBH3 binds to a novel allosteric site in the nucleotide-binding domain (NBD) of Hsp70, by which Bim acts as a positive co-chaperone to promote the ATPase activity and chaperone functions. A dual role of Hsp70's anti-apoptotic function was revealed that when it keeps Bim in check to inhibit apoptosis, it simultaneously stabilizes oncogenic clients including AKT and Raf-1 with the aid of Bim. Two faces of Bim in cell fate regulation were revealed that in opposite to its well-established pro-apoptotic activator role, Bim could help the folding of oncogenic proteins.

中文翻译：

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伴侣 Hsp70 是一种 BH3 受体，由促凋亡 Bim 激活以稳定抗凋亡客户。

伴侣热休克蛋白 70 (Hsp70) 对避免压力下蛋白质错误折叠至关重要，但在多种癌症中也上调，其缓冲细胞压力的能力可防止细胞凋亡。先前的研究表明 Hsp70 与促凋亡 Bcl-2 家族蛋白相互作用，包括 Bim 和 Bax。然而，这种相互作用的明确证明有待于，并且对结构基础和分子机制的了解仍不清楚。早期的研究已经确定了 Bcl-2 家族成员中存在的 Bcl-2 同源 3 (BH3) 结构域，它与受体结合以刺激细胞凋亡。我们现在表明 Hsp70 通过 BH3 域与促凋亡多域和 BH3-only 蛋白物理相互作用，从而作为一种新型 BH3 受体，使用体外荧光极化 (FP)、等温滴定量热法 (ITC)、和基于细胞的免疫共沉淀 (co-IP) 实验、1H-15N-横向弛豫优化光谱 (TROSY-HSQC)、胰蛋白酶蛋白水解、ATPase 活性和变性硫氰酸酶聚集测量进一步证明 BimBH3 与新的变构位点结合Hsp70 的核苷酸结合结构域 (NBD)，Bim 通过该结构域作为阳性共伴侣促进 ATPase 活性和伴侣功能。揭示了 Hsp70 的抗细胞凋亡功能的双重作用，当它控制 Bim 以抑制细胞凋亡时，它同时在 Bi​​m 的帮助下稳定致癌客户，包括 AKT 和 Raf-1。揭示了 Bim 在细胞命运调节中的两个方面，与其公认的促凋亡激活剂作用相反，Bim 可以帮助致癌蛋白的折叠。