TRIB3 Promotes Multiple Myeloma Progression by Stabilizing SSRP1 via USP10-Mediated Deubiquitination

Academic Background

Multiple Myeloma (MM) is the second most common hematologic malignancy globally, characterized by aggressive progression, frequent relapse, and resistance to therapy. Although current multi-drug combination therapies have significantly improved patient survival rates, drug resistance and disease relapse remain major challenges in treatment. Therefore, in-depth research into the pathogenesis, progression mechanisms, and drug resistance mechanisms of MM, as well as the identification of new therapeutic targets, holds significant clinical importance.

In recent years, pseudokinases, a class of proteins lacking catalytic activity but possessing regulatory functions, have gradually become a hotspot in cancer research. TRIB3 (Tribble homolog 3) is an important pseudokinase involved in various cellular processes, including tumor stemness, immune modulation, and autophagy regulation. However, the specific functions and mechanisms of TRIB3 in MM have not been fully elucidated. Additionally, SSRP1 (Structure-specific recognition protein 1), a key component of the chromatin transcription elongation factor FACT complex, plays a crucial role in DNA damage response, cell cycle regulation, and tumor progression. However, the regulatory mechanisms underlying SSRP1 protein stability remain unclear.

This study aims to reveal the function of TRIB3 in MM and its molecular mechanism in regulating SSRP1 stability, as well as to develop novel therapeutic strategies targeting the TRIB3/USP10/SSRP1 complex.

Source of the Paper

This paper was co-authored by Haiqin Wang, Long Liang, Yifang Xie, and others, affiliated with the Department of Hematology at the Second Xiangya Hospital of Central South University, the School of Life Sciences, the Hunan Province Key Laboratory of Basic and Applied Hematology, and the Molecular Science and Biomedicine Laboratory at Hunan University. The paper was published in 2024 in the journal Oncogene, with the DOI: 10.1038/s41388-024-03245-4.

Research Process and Results

1. Expression and Clinical Significance of TRIB3 in MM

The study first analyzed gene expression data from multiple databases (GSE2658, GSE5900, etc.) and found that TRIB3 was significantly upregulated in CD138+ plasma cells from MM patients and was closely associated with poor prognosis. Further quantitative PCR (qPCR) and Western Blot (WB) experiments confirmed that both mRNA and protein levels of TRIB3 were significantly elevated in MM cell lines and patient samples.

2. TRIB3 Promotes MM Cell Proliferation

Through knockdown and overexpression of TRIB3, the study found that TRIB3 knockdown significantly inhibited the proliferation and clonogenic ability of MM cells, while TRIB3 overexpression enhanced these capabilities. Additionally, TRIB3 knockdown induced cell apoptosis. In vivo experiments showed that TRIB3 knockdown significantly inhibited tumor growth in an MM mouse model and prolonged the survival of the mice.

3. Direct Interaction Between TRIB3 and SSRP1

Using co-immunoprecipitation (Co-IP) and mass spectrometry analysis, the study found that TRIB3 directly interacts with SSRP1. Further experiments revealed that TRIB3 binds to the N-terminal domain (NTD) of SSRP1 through its C-terminal kinase-like domain (KDC), thereby regulating SSRP1 stability.

4. TRIB3 Regulates SSRP1 Stability via the Ubiquitin-Proteasome Pathway

The study found that TRIB3 knockdown led to a significant decrease in SSRP1 protein levels, while TRIB3 overexpression increased SSRP1 stability. Further experiments demonstrated that TRIB3 maintains SSRP1 stability by inhibiting its ubiquitin-mediated degradation. Treatment with the proteasome inhibitor MG132 reversed SSRP1 degradation, indicating that TRIB3 regulates SSRP1 stability through the ubiquitin-proteasome pathway.

5. Formation of the TRIB3/USP10/SSRP1 Ternary Complex

The study found that TRIB3 interacts with the deubiquitinating enzyme USP10 and promotes the binding of USP10 to SSRP1, forming a TRIB3/USP10/SSRP1 ternary complex. This complex stabilizes SSRP1 through USP10-mediated deubiquitination, thereby promoting MM cell proliferation.

6. Development of a Stapled Peptide Targeting the TRIB3/USP10/SSRP1 Complex

Based on the structural information of the TRIB3-SSRP1 interaction, the research team designed and synthesized five stapled peptides, among which SP-A exhibited significant anti-MM activity. SP-A effectively disrupted the TRIB3/USP10/SSRP1 complex, leading to SSRP1 degradation and inhibiting MM cell proliferation. Additionally, SP-A showed a significant synergistic effect when combined with the proteasome inhibitor Bortezomib (BTZ), further enhancing the anti-MM efficacy.

Conclusions and Significance

This study reveals the molecular mechanism by which TRIB3 stabilizes SSRP1 through USP10-mediated deubiquitination, thereby promoting MM cell proliferation. The discovery of the TRIB3/USP10/SSRP1 complex provides a new therapeutic target for MM. Furthermore, the developed stapled peptide SP-A effectively disrupts this complex, inhibits MM progression, and exhibits synergistic effects with existing BTZ therapy, holding significant clinical application potential.

Research Highlights

1. TRIB3 as a High-Risk Factor in MM: TRIB3 is significantly upregulated in MM patients and is closely associated with poor prognosis.
2. Discovery of the TRIB3/USP10/SSRP1 Ternary Complex: This complex stabilizes SSRP1 through USP10-mediated deubiquitination, promoting MM cell proliferation.
3. Development of the Stapled Peptide SP-A: SP-A effectively disrupts the TRIB3/USP10/SSRP1 complex, inhibits MM progression, and exhibits synergistic effects with BTZ.

Research Value

This study not only elucidates the function and mechanism of TRIB3 in MM but also provides new targets and strategies for MM treatment. The development of the stapled peptide SP-A offers new possibilities for the clinical treatment of MM, holding significant scientific and application value.