Pseudokinase TRIB3 stabilizes SSRP1 via USP10-mediated deubiquitination to promote multiple myeloma progression.

Multiple myeloma (MM), the world's second most common hematologic malignancy, poses considerable clinical challenges due to its aggressive progression and resistance to therapy. Addressing these challenges requires a detailed understanding of the mechanisms driving MM initiation, progression, and therapeutic resistance. This study identifies the pseudokinase tribble homolog 3 (TRIB3) as a high-risk factor that promotes MM malignancy in vitro and in vivo. Mechanistically, TRIB3 directly interacts with structure-specific recognition protein 1 (SSRP1) and ubiquitin-specific peptidase 10 (USP10), facilitating the formation of a TRIB3/USP10/SSRP1 ternary complex. This complex stabilizes SSRP1 via USP10-mediated deubiquitination, thereby driving MM cell proliferation. Furthermore, a stapled peptide, SP-A, was developed, which effectively disrupts the TRIB3/USP10/SSRP1 complex, leading to a decrease in SSRP1 levels by inhibiting its stabilization through USP10. Notably, SP-A exhibits strong synergistic effects when combined with the proteasome inhibitor bortezomib. Given the critical role of the TRIB3/USP10/SSRP1 complex in MM pathophysiology, it represents a promising therapeutic target for MM treatment. In MM cells, TRIB3, USP10 and SSRP1 form a ternary complex and TRIB3 enhances the deubiquitinating effect of USP10 on SSRP1, leading to malignant progression of MM. In the case of drug intervention, SP-A attenuates the binding of SSRP1 and USP10 by inhibiting protein interactions between TRIB3 and SSRP1 and promoted SSRP1 protein degradation, leading to significant inhibition of MM development. Visual abstract created with Biorender.