title: Rb-dependent cellular senescence, multinucleation and susceptibility to oncogenic transformation through PKC scaffolding by SSeCKS/AKAP12.
abstract: A subset of AKAPs (A Kinase Anchoring Proteins) regulate signaling and cytoskeletal pathways through the spaciotemporal scaffolding of multiple protein kinases (PK) such as PKC and PKA, and associations with the plasma membrane and the actin-based cytoskeleton. SSeCKS/Gravin/Akap12 expression is severely downregulated in many advanced cancers and exhibits tumor- and metastasis-suppressing activity. akap12-null (KO) mice develop prostatic hyperplasia with focal dysplasia, but the precise mechanism how Akap12 prevents oncogenic progression remains unclear. Here, we show that KO mouse embryonic fibroblasts (MEF) exhibit premature senescence marked by polyploidy and multinucleation, and by increased susceptibility to oncogenic transformation. Although p53 and Rb pathways are activated in the absence of Akap12, senescence is dependent on Rb. Senescence is driven by the activation of PKCα, which induces p16(Ink4a)/Rb through a MEK-dependent downregulation of Id1, and PKCδ, which downregulates Lats1/Warts, a mitotic exit network kinase required for cytokinesis. Our data strongly suggest that Akap12 controls Rb-mediated cell aging and oncogenic progression by directly scaffolding and attenuating PKCα/δ.
authors.affiliation: Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, NY, USA.
authors.forename: Shin
authors.initials: S
authors.lastname: Akakura
authors.forename: Peter
authors.initials: P
authors.lastname: Nochajski
authors.forename: Lingqiu
authors.initials: L
authors.lastname: Gao
authors.forename: Paula
authors.initials: P
authors.lastname: Sotomayor
authors.forename: Sei-ichi
authors.initials: S
authors.lastname: Matsui
authors.forename: Irwin H
authors.initials: IH
authors.lastname: Gelman
mesh_terms: D054758:A Kinase Anchor Proteins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D016922:Cellular Senescence; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D015536:Down-Regulation; D005347:Fibroblasts / Q000378:metabolism; D051798:Inhibitor of Differentiation Protein 1 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D011123:Polyploidy; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D054758:A Kinase Anchor Proteins; C491161:Akap12 protein, mouse; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; C497455:Idb1 protein, mouse; D051798:Inhibitor of Differentiation Protein 1; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; C490501:Lats1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta