p53 acetylation in ferroptosis and tumor suppression

项目摘要 p53肿瘤抑制途径的失活是大多数人肿瘤形成中的关键事件。 癌的虽然p53介导的细胞周期阻滞，衰老和凋亡是细胞凋亡的关键障碍。 随着癌症的发展，越来越多的证据表明，p53依赖性细胞周期停滞，细胞凋亡， 衰老不足以消除p53的肿瘤抑制活性。几种小鼠模型 表明在缺乏这些典型功能情况下，可以通过p53实现肿瘤抑制。的p53 蛋白质通过作为DNA结合转录因子选择性地 调节某些p53转录靶基因的表达。许多研究已经证实， p53的乙酰化在p53靶基因表达的启动子特异性激活中起关键信号的作用。值得注意的是， 我们早期的研究表明p533 KR（3 KR：K117 R + K161 R + K162 R）乙酰化缺陷突变体 小鼠模型，其缺乏经历p53介导的凋亡、衰老和细胞周期停滞的能力， 当与p53缺失小鼠相比时，不显著倾向于发展肿瘤。铁凋亡是一种调节性的 由脂质氢过氧化物积累驱动的非凋亡性细胞死亡形式。我们发现p53抑制了 胱氨酸摄取，并通过抑制SLC 7A 11的表达使细胞对铁凋亡敏感，SLC 7A 11是细胞凋亡的关键成分。 胱氨酸/谷氨酸反向转运蛋白。事实上，p533 KR是一种乙酰化缺陷突变体，无法诱导细胞周期 阻止衰老和凋亡，完全保留了调控SLC 7A 11表达和促进 铁性下垂然而，目前还不清楚p53介导的铁凋亡是如何调节的，以及p53-铁凋亡是否与铁凋亡相关。 介导的铁凋亡是其剩余的肿瘤抑制所绝对需要的。在初步研究中，我们 在小鼠p53的赖氨酸K98（或人p53的K101）上鉴定了一个新的p53乙酰化位点。虽然损失 K98乙酰化（p53 K98 R）单独对p53介导的反式激活有非常温和的影响，同时 在所有四个乙酰化位点的突变（p534 KR：K98 R + K117 R + K161 R + K162 R）完全消除了它的能力， 调节代谢靶点，如TIGAR和SLC 7A 11。这里要检验的中心假设是， p53乙酰化在调节p53功能中起主要作用，并且p53介导的铁凋亡是否作为 在不存在细胞周期停滞、凋亡和衰老的情况下抑制肿瘤的关键机制。在Aim中 1，我们将阐明乙酰化在调节p53介导的铁凋亡反应中的分子机制。 和人类癌细胞中的肿瘤生长。在目的2中，我们将研究p53的生理意义， 通过建立一种新的p53突变型（p534 KR/4KR）小鼠， 模型

Project Summary Inactivation of the p53 tumor suppression pathway is a pivotal event in the formation of most human cancers. Although p53-mediated cell-cycle arrest, senescence and apoptosis serve as critical barriers to cancer development, accumulating evidence suggests that loss of p53-dependent cell cycle arrest, apoptosis, and senescence is not sufficient to abrogate the tumor suppression activity of p53. Several mouse models suggest that tumor suppression by p53 can be achieved in the absence of those canonical functions. The p53 protein achieves diverse cellular outcomes by serving as a DNA-binding transcription factor that selectively modulates the expression of certain p53 transcriptional target genes. Numerous studies have established that acetylation of p53 acts as a key signal in promoter-specific activation of p53 target gene expression. Notably, our earlier studies demonstrate that the p533KR (3KR:K117R+K161R+K162R) acetylation-deficient mutant mouse model, which lacks the ability to undergo p53-mediated apoptosis, senescence and cell cycle arrest, are not significantly prone to developing tumors when compared to p53-null mice. Ferroptosis is a regulated form of non-apoptotic cell death driven by accumulation of lipid hydroperoxides. We found that p53 inhibits cystine uptake and sensitizes cells to ferroptosis by repressing expression of SLC7A11, a key component of the cystine/glutamate antiporter. Indeed, p533KR, an acetylation-defective mutant that fails to induce cell-cycle arrest, senescence and apoptosis, fully retains the ability to regulate SLC7A11 expression and promote ferroptosis. Nevertheless, it remains unclear how p53-mediated ferroptosis is regulated and whether p53- mediated ferroptosis is absolutely required for its remaining tumor suppression. In our preliminary studies, we have identified a novel p53 acetylation site at lysine K98 in mouse p53 (or K101 for human p53). While the loss of K98 acetylation (p53K98R) alone has very modest effects on p53-mediated transactivation, simultaneous mutations at all four acetylation sites (p534KR: K98R+K117R+K161R+K162R) completely abolish its ability to regulate metabolic targets such as TIGAR and SLC7A11. The central hypothesis to be tested here is whether p53 acetylation plays a major role in modulating p53 functions and whether p53-mediated ferroptosis is acts as a key mechanism in tumor suppression in the absence of cell-cycle arrest, apoptosis and senescence. In Aim 1, we will elucidate the molecular mechanisms of acetylation in modulating p53-mediated ferroptotic responses and tumor growth in human cancer cells. In Aim 2, we will examine the physiological significance of p53 acetylation as well as p53-mediated ferroptosis in vivo by establishing a new p53-mutant (p534KR/4KR) mouse model.