PRAME promotes proliferation of multiple myeloma cells through CTMP/Akt/p21/CCND3 axis by regulating the ubiquitination of CTMP and p21

Abstract

AbstractBackground Multiple myeloma (MM) is a ubiquitin proteasome system (UPS)-dysfunction disease. We previously reported that the PRAME transcript level at diagnosis was prognostic for MM, which was related to proteasome inhibitor bortezomib treatment. In the present study, we aimed to investigate molecular mechanisms underlying the above clinical performance in MM cells. Methods MM cell lines with PRAME knockdown and overexpression were established by lentivirus transduction. Cell viability, cell cycle analysis, immunohistochemistry staining, cell migration and invasion, colony-forming and xeno-transplant assays were performed to evaluate the biological effects of PRAME on MM cells in vivo and in vitro. Proteomics and IP combined with MS were further performed to explore the downstream signaling. Co-IP, western blot, cycloheximide (CHX)-chase assay, and endogenous ubiquitination assay were utilized to examine the interactions and ubiquitination relations between PRAME and CTMP as well as p21. Assessment of apoptosis and CHX-chase assay were applied to analyze the role of PRAME under the effect of bortezomib on MM cells. Results Proliferation-promoting role of PRAME was demonstrated in MM cell models. CTMP and p21 were found to be the novel targets of PRAME in the Cul2-dependent substrate recognition process. PRAME interacted with and mediated ubiquitination of CTMP and p21, and subsequently elevated p-Akt and CCND3 protein levels, and promoted apoptosis of MM cells under bortezomib treatment. Conclusions PRAME promoted proliferation and increased bortezomib sensibility by regulating ubiquitination and degradation of CTMP and p21, which provided new targets for more precise and effective treatment choices for MM.