Protein and redox homeostasis in cancer development and therapy

项目摘要 蛋白质稳态（proteostasis）和还原-氧化（redox）平衡是两种严格调节的， 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 包括癌症破坏蛋白质稳态和氧化还原平衡是选择性杀伤的有效途径 癌细胞例如，蛋白酶体抑制剂如硼替佐米（Velcade）在治疗糖尿病方面是高度有效的。 治疗多种癌症，并且自噬抑制剂正被积极地用作抗癌治疗剂。 许多临床有效的化疗药物如三氧化二砷可诱导氧化猝发和细胞凋亡， 死亡，据信这至少部分有助于它们的抗癌功效。另一方面，在一项研究中， 失调的蛋白质稳态和氧化还原稳态可通过激活许多促细胞凋亡的蛋白质， 生存/生长信号通路。看似矛盾的作用（促癌和抗癌）通常是 被认为是由强度和持续时间的压力，虽然精确的基础， 机制在很大程度上仍然难以捉摸。泛素结合蛋白p62（SQSTM 1）是其众多的 功能，严格调节蛋白质和氧化还原平衡，通过隔离某些蛋白质， 聚集并将其递送至自噬体进行降解。p62的这种隔离功能依赖于 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。我们最近 报道了TRIM 21（包含三分基序的蛋白21），一种包含RING结构域的泛素E3连接酶， 通过K63-键直接与K7处的p62相互作用并使其泛素化，这消除了K7-D 69氢键 并抑制p62寡聚化、聚集和隔离功能。其中一种客户蛋白质 被p62隔离的是Keap 1，它是一种抗氧化反应的负调节因子， 转录因子Nrf 2。TRIM 21介导的p62 K7泛素化导致Keap 1螯合失败 抑制抗氧化反应相反，TRIM 21缺陷细胞显示增加的p62 寡聚化、蛋白质聚集、Keap 1螯合、Nrf 2活化和抗氧化反应。在这 项目，我们建议研究的假设，TRIM 21功能作为一种应激适应分子，并发挥作用， 在蛋白质平衡和氧化还原稳态中起关键作用，通过泛素化p62和负调节其 螯合功能，为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TRIM 21表达失调并与预后相关， 许多癌症，完成这个项目将揭示TRIM 21作为一个新的重要调节细胞 蛋白质稳态和氧化还原稳态，并将有助于揭示TRIM 21在癌症发展中的作用， 疗法

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.