title: Expression of the cereblon binding protein argonaute 2 plays an important role for multiple myeloma cell growth and survival.
abstract: BACKGROUND
  Immunomodulatory drugs (IMiDs), such as lenalidomide, are therapeutically active compounds that bind and modulate the E3 ubiquitin ligase substrate recruiter cereblon, thereby affect steady-state levels of cereblon and cereblon binding partners, such as ikaros and aiolos, and induce many cellular responses, including cytotoxicity to multiple myeloma (MM) cells. Nevertheless, it takes many days for MM cells to die after IMiD induced depletion of ikaros and aiolos and thus we searched for other cereblon binding partners that participate in IMiD cytotoxicity.
  
  
  METHODS
  Cereblon binding partners were identified from a MM cell line expressing histidine-tagged cereblon by pulling down cereblon and its binding partners and verified by co-immunoprecipitation. IMiD effects were determined by western blot analysis, cell viability assay, microRNA array and apoptosis analysis.
  
  
  RESULTS
  We identified argonaute 2 (AGO2) as a cereblon binding partner and found that the steady-state levels of AGO2 were regulated by cereblon. Upon treatment of IMiD-sensitive MM cells with lenalidomide, the steady-state levels of cereblon were significantly increased, whereas levels of AGO2 were significantly decreased. It has been reported that AGO2 plays a pivotal role in microRNA maturation and function. Interestingly, upon treatment of MM cells with lenalidomide, the steady-state levels of microRNAs were significantly altered. In addition, silencing of AGO2 in MM cells, regardless of sensitivity to IMiDs, significantly decreased the levels of AGO2 and microRNAs and massively induced cell death.
  
  
  CONCLUSIONS
  These results support the notion that the cereblon binding partner AGO2 plays an important role in regulating MM cell growth and survival and AGO2 could be considered as a novel drug target for overcoming IMiD resistance in MM cells.
authors.affiliation: Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ, 85259, USA.|Zhejiang Provincial Key Laboratory of Nephrology, Hangzhou Traditional Chinese Medical Hospital, 453 Tiyuchang Rd, Hangzhou, 310007, China.
authors.forename: Qinqin
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ, 85259, USA.
authors.forename: Yue-xian
authors.initials: YX
authors.lastname: Hou
authors.affiliation: Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ, 85259, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Langlais
authors.affiliation: Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ, 85259, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Erickson
authors.affiliation: Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ, 85259, USA.
authors.forename: James
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Division of Hematology-Oncology, Mayo Clinic Arizona, Scottsdale, AZ, USA.
authors.forename: Chang-Xin
authors.initials: CX
authors.lastname: Shi
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University, Tempe, AZ, USA.
authors.forename: Moulun
authors.initials: M
authors.lastname: Luo
authors.affiliation: Division of Hematology-Oncology, Mayo Clinic Arizona, Scottsdale, AZ, USA.
authors.forename: Yuanxiao
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ, 85259, USA.|Key Laboratory of Carcinogenesis and Translational Research, Breast Center, Beijing Cancer Hospital & Institute, Peking University Cancer Hospital, Beijing, 100142, P. R. China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University, Tempe, AZ, USA.|Department of Medicine, Mayo Clinic Arizona, Scottsdale, AZ, USA.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Mandarino
authors.affiliation: Division of Hematology-Oncology, Mayo Clinic Arizona, Scottsdale, AZ, USA.
authors.forename: Keith
authors.initials: K
authors.lastname: Stewart
authors.affiliation: Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ, 85259, USA. xbchang@mayo.edu.
authors.forename: Xiu-bao
authors.initials: XB
authors.lastname: Chang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000235:genetics; D060565:Argonaute Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000235:genetics*; D002470:Cell Survival / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D000077269:Lenalidomide; D035683:MicroRNAs / Q000096:biosynthesis; D009101:Multiple Myeloma / Q000235:genetics* / Q000473:pathology; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D013792:Thalidomide / Q000008:administration & dosage / Q000031:analogs & derivatives; D044767:Ubiquitin-Protein Ligases
chemical_list: C466422:AGO2 protein, human; D048868:Adaptor Proteins, Signal Transducing; D060565:Argonaute Proteins; C502543:CRBN protein, human; D035683:MicroRNAs; D013792:Thalidomide; D044767:Ubiquitin-Protein Ligases; D010447:Peptide Hydrolases; D000077269:Lenalidomide
keywords: Argonaute 2 (AGO2); Cereblon (CRBN); Immunomodulatory drug (IMiD); Lenalidomide; MicroRNA (miRNA); Multiple myeloma (MM)