title: A novel splice variant of calcium and integrin-binding protein 1 mediates protein kinase D2-stimulated tumour growth by regulating angiogenesis.
abstract: Protein kinase D2 (PKD2) is a member of the PKD family of serine/threonine kinases, a subfamily of the CAMK super-family. PKDs have a critical role in cell motility, migration and invasion of cancer cells. Expression of PKD isoforms is deregulated in various tumours and PKDs, in particular PKD2, have been implicated in the regulation of tumour angiogenesis. In order to further elucidate the role of PKD2 in tumours, we investigated the signalling context of this kinase by performing an extensive substrate screen by in vitro expression cloning (IVEC). We identified a novel splice variant of calcium and integrin-binding protein 1, termed CIB1a, as a potential substrate of PKD2. CIB1 is a widely expressed protein that has been implicated in angiogenesis, cell migration and proliferation, all important hallmarks of cancer, and CIB1a was found to be highly expressed in various cancer cell lines. We identify Ser(118) as the major PKD2 phosphorylation site in CIB1a and show that PKD2 interacts with CIB1a via its alanine and proline-rich domain. Furthermore, we confirm that CIB1a is indeed a substrate of PKD2 also in intact cells using a phosphorylation-specific antibody against CIB1a-Ser(118). Functional analysis of PKD2-mediated CIB1a phosphorylation revealed that on phosphorylation, CIB1a mediates tumour cell invasion, tumour growth and angiogenesis by mediating PKD-induced vascular endothelial growth factor secretion by the tumour cells. Thus, CIB1a is a novel mediator of PKD2-driven carcinogenesis and a potentially interesting therapeutic target.
authors.affiliation: 1] Department of Internal Medicine I, University of Ulm, Ulm, Baden-Wuerttemberg, Germany [2] Department of Internal Medicine I, Martin-Luther-University Halle-Wittenberg, Halle(Saale), Germany.
authors.forename: M
authors.initials: M
authors.lastname: Armacki
authors.affiliation: Department of Internal Medicine I, Martin-Luther-University Halle-Wittenberg, Halle(Saale), Germany.
authors.forename: G
authors.initials: G
authors.lastname: Joodi
authors.affiliation: Department of Internal Medicine I, Martin-Luther-University Halle-Wittenberg, Halle(Saale), Germany.
authors.forename: S C
authors.initials: SC
authors.lastname: Nimmagadda
authors.affiliation: 1] Academic Medical Center (AMC), University of Amsterdam, Amsterdam, The Netherlands [2] Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: de Kimpe
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: G V
authors.initials: GV
authors.lastname: Pusapati
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Vandoninck
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, KU Leuven, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Van Lint
authors.affiliation: Department of Internal Medicine I, University of Ulm, Ulm, Baden-Wuerttemberg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Illing
authors.affiliation: 1] Department of Internal Medicine I, University of Ulm, Ulm, Baden-Wuerttemberg, Germany [2] Department of Internal Medicine I, Martin-Luther-University Halle-Wittenberg, Halle(Saale), Germany.
authors.forename: T
authors.initials: T
authors.lastname: Seufferlein
mesh_terms: D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049033:Chorioallantoic Membrane / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009389:Neovascularization, Pathologic / Q000235:genetics*; D010766:Phosphorylation / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics*; D050396:TRPP Cation Channels / Q000235:genetics* / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics* / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D050396:TRPP Cation Channels; D042461:Vascular Endothelial Growth Factor A; C109198:CIB1 protein, human; C467484:VEGFA protein, human