Defining the role of BH3-only proteins in mitotic and post-mitotic cell death

微管靶向药物（mta）是许多人类恶性肿瘤的标准治疗方法，包括血癌、乳腺癌、卵巢癌和肺癌。它们的作用模式包括通过干扰有丝分裂纺锤体动力学导致纺锤体组装检查点（SAC）的激活而延长有丝分裂停滞。SAC的执行包括在着丝点组装含有MAD2、Bub3和BubR1的有丝分裂检查点复合体（MCC），驱动后期促进复合体（APC）共激活子CDC20的降解，从而阻止有丝分裂退出。在有丝分裂中停滞的细胞通常会经历两种不同的命运，一种是仅涉及bh3蛋白BIM、BID和NOXA的细胞死亡，这可以通过核溶酶体激活来实现，另一种是检查点适应（滑移）。后者发生在CyclinB水平低于临界阈值时，由于非规范apc驱动的蛋白质降解，这通常与BCL2家族促凋亡介质的减少相关。这导致有丝分裂过早退出和细胞凋亡逃逸，通常处于多倍体状态。众所周知，这些细胞由于染色体的不忠实分离导致染色体不稳定（CIN）而变得遗传不稳定。这种染色体不稳定（癌症）细胞的命运通常由肿瘤抑制因子p53调控，它的激活可能导致有丝分裂后细胞死亡（有丝分裂突变）或细胞衰老，其分子机制迄今尚不明确。在缺乏p53的情况下，这些细胞可以逃脱这些控制机制，导致非整倍体克隆的产生和扩增，形成肿瘤进化、疾病进展和最终耐药性的基础。本提案的目的是：(1)确定与有丝分裂和有丝分裂后细胞死亡相关的BH3-only蛋白活性的控制机制；(2)探究bcl2调节的有丝分裂内和有丝分裂外细胞死亡作为抗非整倍体和癌症的屏障的作用。

Microtubule-targeting agents (MTAs) are standard of care for a number of human malignancies including blood, breast, ovarian and lung cancer. Their mode of action includes prolonged mitotic arrest by interfering with mitotic spindle dynamics that leads to the activation of the spindle assembly checkpoint (SAC). SAC execution involves assembly of the mitotic checkpoint complex (MCC) containing MAD2, Bub3 and BubR1 at kinetochores, driving degradation of the Anaphase-promoting complex (APC) co-activator, CDC20, thereby preventing mitotic exit. Cells stalled in mitosis usually can undergo two different fates, either cell death involving the BH3-only proteins BIM, BID and NOXA that can be paralleled by Ripoptosome activation, or, alternatively, checkpoint adaptation (slippage). The latter occurs when CyclinB levels fall below a critical threshold, due to non-canonical APC-driven protein degradation, that often correlates with a concomitant reduction of pro-apoptotic mediators of the BCL2 family. This leads to premature mitotic exit and escape from apoptosis, often in a polyploid state. Such cells are well known to become genetically instable due to unfaithful segregation of chromosomes leading to chromosomal instability (CIN). The fate of such chromosomally instable (cancer) cells is usually regulated by the tumor suppressor p53 and its activation can either result in post-mitotic cell death, by so-far poorly defined molecular mechanisms (mitotic catastrophe), or cellular senescence. In the absence of p53, such cells can escape these control mechanisms, leading to the creation and expansion of aneuploid clones that form the basis of tumor evolution, progressive disease and ultimately also drug-resistance. The aim of this proposal is to (i) define the mechanisms controlling activity of BH3-only proteins relevant in mitotic and post-mitotic cell death and to (ii) interrogate the contribution of BCL2-regulated cell death in and out of mitosis as a barrier against aneuploidy and cancer.