Abstract 2620: TRIM4 is the E3 ubiquitin-ligase for TPL2/MAP3K8 and is modulated by oncogenic KRAS

Abstract TPL2 (tumor progression locus 2, a. k. a. Cot/MAP3K8) kinase becomes oncogenic via disruption of the C-terminus, which abrogates its proteasomal degradation. However, the mechanism underlying degradation of TPL2 remains unclear. Using proximity-dependent biotin identification (BioID), for the first time we have discovered that Tripartite Motif Containing 4 (TRIM4) is the E3-ligase that binds and degrades TPL2 via polyubiquitination of lysine 415 and 439. Notably, naturally-occurring oncogenic R442H and E188K mutations in TPL2 abrogated the binding and polyubiquitination by TRIM4. Furthermore, KRAS oncoprotein stabilizes TPL2 by promoting TRIM4 degradation. Using immunoprecipitation-mass spectrometry, we identified TRIM21 as a ligase that binds and stabilizes TRIM4, in part by reducing TRIM4 polyubiquitination. Therefore, oncogenic KRAS binds to and promotes TRIM21 degradation, destabilizing TRIM4 and prolonging the half-life of TPL2. Overall, we discovered novel mechanisms of TPL2 regulation which are influenced by oncogenic KRAS, providing opportunities for the development of novel therapies. [S. Bansod and P.B. Dodhiawala contributed equally to this work.] Citation Format: Sapana Prakashrao Bansod, Paarth B. Dodhiawala, Ashenafi Bulle, Peng Liu, Lin Li, Patrick M. Grierson, Jason Held, Kian-Huat Lim. TRIM4 is the E3 ubiquitin-ligase for TPL2/MAP3K8 and is modulated by oncogenic KRAS [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2620.