Protein and redox homeostasis in cancer development and therapy

项目总结 蛋白质稳态(蛋白质稳态)和还原-氧化(氧化还原)平衡是两个受到严格调控的 相互关联的分子事件。它们在许多生理/病理条件下起着关键作用。 包括癌症。破坏蛋白平衡和氧化还原平衡是选择性杀伤的有效途径 癌细胞。例如，蛋白酶体抑制剂，如Bortezomib(Velade)，在 治疗多种癌症和自噬抑制剂正被作为抗癌治疗药物而积极研究。 许多临床有效的化疗药物，如三氧化二砷，可引起氧化猝发和细胞 死亡，这被认为至少在一定程度上有助于它们的抗癌效果。另一方面， 调节失调的蛋白平衡和氧化还原平衡可通过激活许多促癌基因而促进肿瘤的发生 生存/生长信号通路。看似矛盾的影响(促癌和抗癌)通常是 被认为是由压力的强度和持续时间所解释的，尽管准确的潜在原因 机制在很大程度上仍然难以捉摸。泛素结合蛋白p62(SQSTM1)，在其众多的 功能，关键地调节蛋白质平衡和氧化还原平衡，通过将某些蛋白质隔离在 聚集并将它们运送到自噬小体进行降解。P62的这种封存功能依赖于 通过赖氨酸(K)7和天冬氨酸(D)69残基之间的氢键进行二聚化。我们最近 报道了TRIM21(Triartite Motif-Containing Protein 21)，一种含有环状结构域的泛素E3连接酶， 通过K63-链直接与K7上的p62相互作用并泛素化，从而取消K7-D69氢键 并抑制p62的寡聚、聚集和封存功能。其中一种客户蛋白 被p62隔离的是Keap1，它是抗氧化反应的负调节因子，抑制抗氧化剂。 转录因子Nrf2。TRIM21介导的p62 K7泛素化导致Keap1封存失败 并抑制抗氧化剂反应。相反，缺乏TRIM21的细胞显示p62增加 寡聚，蛋白质聚集，Keap1封存，Nrf2激活，和抗氧化反应。在这 项目中，我们建议研究TRIM21作为一种压力适应分子并发挥作用的假说。 在蛋白平衡和氧化还原动态平衡中的关键作用，通过泛素化p62和负调控其 隔离功能，对于潜在的机制和生物学意义，主要侧重于抗 癌症治疗和肿瘤发生。由于TRIM21的表达异常，并与预后相关 无数的癌症，完成这个项目将发现TRIM21作为一种新的细胞重要调节因子 蛋白平衡和氧化还原动态平衡，将有助于揭示TRIM21在癌症发生和发展中的作用。 心理治疗。

PROJECT SUMMARY Protein homeostasis (proteostasis) and reduction-oxidation (redox) balance are two tightly regulated and mutually associated molecular events. They play crucial roles in many physiological/pathological conditions including cancer. Disruption of proteostasis and redox balance is an effective approach to selectively kill cancer cells. For examples, proteasome inhibitors such as Bortezomib (Velcade) are highly effective in treating numerous cancers, and autophagy inhibitors are being actively pursued as anti-cancer therapeutics. Many clinically effective chemotherapeutic agents such as arsenic trioxide can induce oxidative burst and cell death, which is believed to contribute, at least in part, to their anti-cancer effectiveness. On the other hand, dysregulated proteostasis and redox homeostasis can contribute to oncogenesis by activating numerous pro- survival/growth signaling pathways. The seemingly paradoxical effects (pro- and anti-cancer) are generally thought to be accounted for by the intensity and duration of the stresses, although the precise underlying mechanisms remain largely elusive. The ubiquitin-binding protein, p62 (SQSTM1), among its numerous functions, critically regulates both proteostasis and redox balance, by sequestering certain proteins in aggregates and delivering them to autophagosomes for degradation. This sequestration function of p62 relies on its dimmerization via the hydrogen bond between lysine (K)7 and aspartate (D)69 residues. We recently reported that TRIM21 (Tripartite motif-containing protein 21), a RING domain-containing ubiquitin E3 ligase, directly interacts with and ubiquitylates p62 at K7 via K63-linkage, which abolishes the K7-D69 hydrogen bond and inhibits p62 oligomerization, aggregation, and sequestration functions. One of the client proteins sequestered by p62 is Keap1, a negative regulator of the antioxidant response that suppresses the antioxidant transcription factor Nrf2. TRIM21-mediated p62 K7 ubiquitylation leads to the failure of Keap1 sequestration and suppressed antioxidant response. Conversely, TRIM21-deficient cells display increased p62 oligomerization, protein aggregation, Keap1 sequestration, Nrf2 activation, and antioxidant response. In this project, we propose to study the hypothesis that TRIM21 functions as a stress-adaptation molecule and plays a crucial role in proteostasis and redox homeostasis, by ubiquitylating p62 and negatively regulating its sequestration function, for the underlying mechanisms and biological significance, with a main focus on anti- cancer therapy and oncogenesis. As TRIM21 expression is dysregulated and correlates with prognosis in numerous cancers, accomplishing this project will uncover TRIM21 as a new important regulator for cellular proteostasis and redox homeostasis, and will help reveal the role of TRIM21 in cancer development and therapy.