TPL2 激酶 C 末端的功能丧失突变通过阻止其蛋白酶体降解来促进肿瘤发生，从而导致持续的蛋白质表达。然而，TPL2 的降解机制仍然难以捉摸。通过邻近依赖性生物素鉴定 (BioID)，我们发现含有三部分基序的 4 (TRIM4) 作为 E3 连接酶，通过赖氨酸 415 和 439 的多泛素化结合并降解 TPL2。天然存在的 TPL2 突变体 R442H 和 E188K 表现出 TRIM4 结合受损，增强其稳定性。我们进一步发现 TRIM4 本身被另一种 E3 连接酶 TRIM21 稳定，而 TRIM21 又受 KRAS 调节。突变体 KRAS 招募 RNF185 来降解 TRIM21，随后降解 TRIM4，从而稳定 TPL2。在突变型 KRAS 存在的情况下，TPL2 磷酸化并降解 GSK3β，从而导致 β-连环蛋白稳定并激活 Wnt 通路。这些发现阐明了调节 TPL2 的生理机制及其突变 KRAS 对其的利用，强调了开发用于 KRAS 突变癌症的 TPL2 抑制剂的必要性。版权所有 © 2024 作者。由爱思唯尔公司出版。保留所有权利。

Loss-of-function mutations in the C terminus of TPL2 kinase promote oncogenesis by impeding its proteasomal degradation, leading to sustained protein expression. However, the degradation mechanism for TPL2 has remained elusive. Through proximity-dependent biotin identification (BioID), we uncovered tripartite motif-containing 4 (TRIM4) as the E3 ligase that binds and degrades TPL2 by polyubiquitination of lysines 415 and 439. The naturally occurring TPL2 mutants R442H and E188K exhibit impaired TRIM4 binding, enhancing their stability. We further discovered that TRIM4 itself is stabilized by another E3 ligase, TRIM21, which in turn is regulated by KRAS. Mutant KRAS recruits RNF185 to degrade TRIM21 and subsequently TRIM4, thereby stabilizing TPL2. In the presence of mutant KRAS, TPL2 phosphorylates and degrades GSK3β, resulting in β-catenin stabilization and activation of the Wnt pathway. These findings elucidate the physiological mechanisms regulating TPL2 and its exploitation by mutant KRAS, underscoring the need to develop TPL2 inhibitors for KRAS-mutant cancers.Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.