title: Fbxo45-mediated degradation of the tumor-suppressor Par-4 regulates cancer cell survival.
abstract: Prostate apoptosis response protein 4 (Par-4) also known as PRKC apoptosis WT1 regulator is a tumor suppressor that selectively induces apoptosis in cancer cells. However, its post-translational regulation by ubiquitin-mediated proteolysis and the cellular machinery that is responsible for its proteasomal degradation are unknown. Using immunopurification and an unbiased mass spectrometry-based approach, we show that Par-4 interacts with the SPRY-domain containing E3 ubiquitin ligase Fbxo45 through a short consensus sequence motif. Fbxo45 interacts with Par-4 in the cytoplasm and mediates its ubiquitylation and proteasomal degradation. Fbxo45 silencing results in stabilization of Par-4 with increased apoptosis. Importantly, a Par-4 mutant that is unable to bind Fbxo45 is stabilized and further enhances staurosporine-induced apoptosis. Co-expression of Fbxo45 with Par-4 protects cancer cells against Par-4-induced apoptosis. Our studies reveal that Fbxo45 is the substrate-receptor subunit of a functional E3 ligase for Par-4 that has a critical role in cancer cell survival.
authors.affiliation: Department of Pathology, University of Michigan Medical School, 2037 BSRB 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Pathology, University of Michigan Medical School, 2037 BSRB 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Sahasrabuddhe
authors.affiliation: ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT 84108, USA.
authors.forename: P
authors.initials: P
authors.lastname: Szankasi
authors.affiliation: Department of Pathology, University of Michigan Medical School, 2037 BSRB 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
authors.forename: F
authors.initials: F
authors.lastname: Chung
authors.affiliation: Department of Pathology, University of Michigan Medical School, 2037 BSRB 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
authors.forename: V
authors.initials: V
authors.lastname: Basrur
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, KY 40508, USA.
authors.forename: V M
authors.initials: VM
authors.lastname: Rangnekar
authors.affiliation: 1] Department of Pathology, NYU Cancer Institute, New York University School of Medicine, 522 First Avenue, SRB1107, New York, NY 10016, USA [2] Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
authors.forename: M
authors.initials: M
authors.lastname: Pagano
authors.affiliation: 1] Department of Pathology, University of Michigan Medical School, 2037 BSRB 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA [2] Protein Folding Disease Initiative, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Lim
authors.affiliation: 1] Department of Pathology, University of Michigan Medical School, 2037 BSRB 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA [2] Protein Folding Disease Initiative, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA [3] Center for Computational Medicine and Bioinformatics, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109, USA.
authors.forename: K S J
authors.initials: KS
authors.lastname: Elenitoba-Johnson
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D053487:DEAD-box RNA Helicases / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009369:Neoplasms / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D034741:RNA, Small Interfering; D019311:Staurosporine / Q000494:pharmacology; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D051017:Apoptosis Regulatory Proteins; D004791:Enzyme Inhibitors; D044783:F-Box Proteins; C503710:FBXO45 protein, human; D034741:RNA, Small Interfering; C101296:prostate apoptosis response-4 protein; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C498288:DDX4 protein, human; D053487:DEAD-box RNA Helicases; D019311:Staurosporine