Boosen Meike, Vetterkind Susanne, Koplin Ansgar, Illenberger Susanne, Preuss Ute
Institute of Genetics, University of Bonn, Römerstr. 164, D-53117 Bonn, Germany.
Exp Cell Res. 2005 Dec 10;311(2):177-91. doi: 10.1016/j.yexcr.2005.09.010. Epub 2005 Oct 14.
Par-4 (prostate apoptosis response-4) sensitizes cells to apoptotic stimuli, but the exact mechanisms are still poorly understood. Using Par-4 as bait in a yeast two-hybrid screen, we identified Amida as a novel interaction partner, a ubiquitously expressed protein which has been suggested to be involved in apoptotic processes. Complex formation of Par-4 and Amida occurs in vitro and in vivo and is mediated via the C-termini of both proteins, involving the leucine zipper of Par-4. Amida resides mainly in the nucleus but displays nucleo-cytoplasmic shuttling in heterokaryons. Upon coexpression with Par-4 in REF52.2 cells, Amida translocates to the cytoplasm and is recruited to actin filaments by Par-4, resulting in enhanced induction of apoptosis. The synergistic effect of Amida/Par-4 complexes on the induction of apoptosis is abrogated when either Amida/Par-4 complex formation or association of these complexes with the actin cytoskeleton is impaired, indicating that the Par-4-mediated relocation of Amida to the actin cytoskeleton is crucial for the pro-apoptotic function of Par-4/Amida complexes in REF52.2 cells. The latter results in enhanced phosphorylation of the regulatory light chain of myosin II (MLC) as has previously been shown for Par-4-mediated recruitment of DAP-like kinase (Dlk), suggesting that the recruitment of nuclear proteins involved in the regulation of apoptotic processes to the actin filament system by Par-4 represents a potent mechanism how Par-4 can trigger apoptosis.
Par-4（前列腺凋亡反应蛋白4）可使细胞对凋亡刺激敏感，但确切机制仍知之甚少。在酵母双杂交筛选中，我们以Par-4为诱饵，鉴定出Amida是一种新的相互作用蛋白，它是一种普遍表达的蛋白质，据推测参与凋亡过程。Par-4与Amida的复合物在体外和体内均可形成，且通过两种蛋白质的C末端介导，涉及Par-4的亮氨酸拉链。Amida主要定位于细胞核，但在异核体中表现出核质穿梭。在REF52.2细胞中与Par-4共表达时，Amida易位至细胞质并被Par-4招募至肌动蛋白丝，从而增强凋亡诱导。当Amida/Par-4复合物形成或这些复合物与肌动蛋白细胞骨架的结合受损时，Amida/Par-4复合物对凋亡诱导的协同作用被消除，这表明Par-4介导的Amida向肌动蛋白细胞骨架的重新定位对于REF52.2细胞中Par-4/Amida复合物的促凋亡功能至关重要。后者导致肌球蛋白II调节轻链（MLC）的磷酸化增强，正如之前Par-4介导的DAP样激酶（Dlk）招募所显示的那样，这表明Par-4将参与凋亡过程调节的核蛋白招募至肌动蛋白丝系统是Par-4触发凋亡的一种有效机制。
