CRIP1 Involves the Pathogenesis of Multiple Myeloma Via Dual-Regulation of Proteasome and Autophagy

Multiple myeloma (MM) is an incurable hematological malignancy of plasma cells. The maintenance of protein homeostasis is critical for the survival of MM cells. Elevated paraprotein in MM cells would be cleared by proteasomes or lysosomes, which are independent but inter-connected with each other. Proteasome inhibitors (PIs) work as the backbone agent and successfully improved the outcome of patients, but the increasing activity of autophagy suppresses the sensitivity to PIs treatment. In the present study, we elucidated that CRIP1 was a critical player in protein homeostasis via the dual regulation of proteasome and autophagy in MM. A combination analysis of RNA-seq, Co-IP and Tandem affinity purification/mass spectrometry identified that high-level CRIP1 represents a biomarker for relapsed/refractory MM with shorter overall-survival of patients. CRIP1 plays a critical role in MM progression and PIs resistance by binding to deubiquitinase USP7 and proteasome coactivator PA200. CRIP1 promotes proteasome activity and autophagosome maturation in MM by stabilizing PA200. Therefore, our findings clarified the pivotal roles of CRIP1/USP7/PA200 complex formation in ubiquitin-dependent proteasome degradation and autophagy maturation involved in the progression of MM.