title: Molecular characterization of protein kinase C delta (PKCδ)-Smac interactions.
abstract: Protein kinase C δ (PKCδ) is known to be an important regulator of apoptosis, having mainly pro- but also anti-apoptotic effects depending on context. In a previous study, we found that PKCδ interacts with the pro-apoptotic protein Smac. Smac facilitates apoptosis by suppressing inhibitor of apoptosis proteins (IAPs). We previously established that the PKCδ-Smac complex dissociates during induction of apoptosis indicating a functional importance. Because the knowledge on the molecular determinants of the interaction is limited, we aimed at characterizing the interactions between PKCδ and Smac.
  
  
  
  We found that PKCδ binds directly to Smac through its regulatory domain. The interaction is enhanced by the PKC activator TPA and seems to be independent of PKCδ catalytic activity since the PKC kinase inhibitor GF109203X did not inhibit the interaction. In addition, we found that C1 and C2 domains from several PKC isoforms have Smac-binding capacity.
  
  
  
  Our data demonstrate that the Smac-PKCδ interaction is direct and that it is facilitated by an open conformation of PKCδ. The binding is mediated via the PKCδ regulatory domain and both the C1 and C2 domains have Smac-binding capacity. With this study we thereby provide molecular information on an interaction between two apoptosis-regulating proteins.
authors.affiliation: Lund University, Translational Cancer Research, Medicon Village, Building 404:C3, SE-22363, Lund, Sweden.
authors.forename: Christian
authors.initials: C
authors.lastname: Holmgren
authors.affiliation: Lund University, Translational Cancer Research, Medicon Village, Building 404:C3, SE-22363, Lund, Sweden.
authors.forename: Louise
authors.initials: L
authors.lastname: Cornmark
authors.affiliation: Lund University, Translational Cancer Research, Medicon Village, Building 404:C3, SE-22363, Lund, Sweden.
authors.forename: Gry Kalstad
authors.initials: GK
authors.lastname: Lønne
authors.affiliation: Lund University, Translational Cancer Research, Medicon Village, Building 404:C3, SE-22363, Lund, Sweden.
authors.forename: Katarzyna Chmielarska
authors.initials: KC
authors.lastname: Masoumi
authors.affiliation: Lund University, Translational Cancer Research, Medicon Village, Building 404:C3, SE-22363, Lund, Sweden. Christer.Larsson@med.lu.se.
authors.forename: Christer
authors.initials: C
authors.lastname: Larsson
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D019556:COS Cells; D002522:Chlorocebus aethiops; D006801:Humans; D047468:Immunoprecipitation; D007211:Indoles / Q000737:chemistry / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D061986:MCF-7 Cells; D008301:Maleimides / Q000737:chemistry / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D000072417:Protein Domains; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D051745:Protein Kinase C-delta / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D008301:Maleimides; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D051745:Protein Kinase C-delta; C070515:bisindolylmaleimide I
keywords: Co-immunoprecipitation; Protein interaction; Protein kinase C; Smac