Rouchidane Eyitayo Akandé, Daury Laetitia, Priault Muriel, Manon Stéphen
CNRS, Université de Bordeaux, UMR 5095, IBGC, Bordeaux, France.
CNRS, Université de Bordeaux, UMR 5248, CBMN, Pessac, France.
Cell Death Discov. 2024 Jul 23;10(1):335. doi: 10.1038/s41420-024-02108-x.
Membrane insertion of the pro-apoptotic protein Bax was investigated by setting up cell-free synthesis of full-length Bax in the presence of pre-formed nanodiscs. While Bax was spontaneously poorly inserted in nanodiscs, co-synthesis with the mitochondrial receptor Tom22 stimulated Bax membrane insertion. The initial interaction of Bax with the lipid bilayer exposed the hydrophobic GALLL motif in Hα1 leading to Bax precipitation through hydrophobic interactions. The same motif was recognized by Tom22, triggering conformational changes leading to the extrusion and the ensuing membrane insertion of the C-terminal hydrophobic Hα9. Tom22 was also required for Bax-membrane insertion after Bax was activated either by BH3-activators or by its release from Bcl-xL by WEHI-539. The effect of Tom22 was impaired by DY substitution in Bax-Hα7 and TP substitution in Bax-Hα9, which are found in several tumors. Conversely, a RE substitution promoted a spontaneous insertion of Bax in nanodiscs, in the absence of Tom22. Both Tom22-activated Bax and BaxRE alone permeabilized liposomes to dextran-10kDa and formed ~5-nm-diameter pores in nanodiscs. The concerted regulation of Bax membrane insertion by Tom22 and BH3-activators is discussed.
通过在预先形成的纳米盘存在的情况下建立全长Bax的无细胞合成，研究了促凋亡蛋白Bax的膜插入情况。虽然Bax在纳米盘中自发插入效率很低，但与线粒体受体Tom22共同合成可刺激Bax的膜插入。Bax与脂质双层的初始相互作用使Hα1中的疏水GALLL基序暴露，导致Bax通过疏水相互作用沉淀。Tom22识别相同的基序，引发构象变化，导致C末端疏水Hα9的挤出和随后的膜插入。当Bax被BH3激活剂激活或被WEHI-539从Bcl-xL中释放后，Tom22对于Bax的膜插入也是必需的。在几种肿瘤中发现的Bax-Hα7中的DY取代和Bax-Hα9中的TP取代会损害Tom22的作用。相反，RE取代促进了在没有Tom22的情况下Bax在纳米盘中的自发插入。Tom22激活的Bax和单独的BaxRE都能使脂质体对10 kDa葡聚糖通透，并在纳米盘中形成直径约5 nm的孔。本文讨论了Tom22和BH3激活剂对Bax膜插入的协同调节作用。
