title: Progestin-inducible EDD E3 ubiquitin ligase binds to α4 phosphoprotein to regulate ubiquitination and degradation of protein phosphatase PP2Ac.
abstract: Mammalian α4 phosphoprotein binds to the protein phosphatase 2A catalytic subunit (PP2Ac) to regulate PP2A activity, and to poly(A)-binding protein (PABP) and progestin-inducible EDD E3 ubiquitin ligase. This study showed induction of the EDD protein by progesterone, 17β-estradiol and prolactin in breast cancer cells. Co-immunoprecipitation analyses, using lysates of COS-1 cells transfected with α4-deletion constructs, showed the α4 N-terminus binding to endogenous PP2Ac and PABP, and the C-terminus to EDD. Monoubiquitinated α4 in MCF-7 cells was unaffected by EDD-targeting siRNA (siEDD) nor by non-targetting siNT, thus, EDD does not ubiquitinate α4. PP2Ac is polyubiquitinated, and 36-kDa PP2Ac only was detected in siEDD- or siNT-transfected cells. However, treatment with proteasomal inhibitor MG132 showed polyubiquitinated-PP2Ac molecules (∼65-250kDa) abundantly in siNT controls but low in siEDD-transfectants, implicating PP2Ac as an EDD substrate. Finally, progesterone induction of EDD in MCF-7 cells correlated with decreased PP2Ac levels, further implicating hormone-inducible EDD in PP2Ac turnover.
authors.affiliation: Department of Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: William J
authors.initials: WJ
authors.lastname: McDonald
authors.affiliation: Department of Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Lynn N
authors.initials: LN
authors.lastname: Thomas
authors.affiliation: Department of Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Samir
authors.initials: S
authors.lastname: Koirala
authors.affiliation: Department of Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Obstetrics & Gynaecology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada. Electronic address: ctoo@dal.ca.
authors.forename: Catherine K L
authors.initials: CKL
authors.lastname: Too
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D019556:COS Cells; D002522:Chlorocebus aethiops; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D061986:MCF-7 Cells; D018832:Molecular Chaperones; D050505:Mutant Proteins / Q000378:metabolism; D039102:Poly(A)-Binding Proteins / Q000378:metabolism; D025821:Polyubiquitin / Q000378:metabolism; D011372:Progestins / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D059748:Proteolysis / Q000187:drug effects*; D013379:Substrate Specificity / Q000187:drug effects; D044767:Ubiquitin-Protein Ligases / Q000096:biosynthesis*; D054875:Ubiquitination / Q000187:drug effects*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C490467:IGBP1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D018832:Molecular Chaperones; D050505:Mutant Proteins; D039102:Poly(A)-Binding Proteins; D011372:Progestins; D025821:Polyubiquitin; C117617:UBR5 protein, human; D044767:Ubiquitin-Protein Ligases; D054648:Protein Phosphatase 2
keywords: 17β-Estradiol; EDD E3 Ubiquitin ligase; PP2Ac; Progesterone; Prolactin; α4 Phosphoprotein