title: AKT-dependent phosphorylation of the SAM domain induces oligomerization and activation of the scaffold protein CNK1.
abstract: Scaffold proteins are hubs for the coordination of intracellular signaling networks. The scaffold protein CNK1 promotes several signal transduction pathway. Here we demonstrate that sterile motif alpha (SAM) domain-dependent oligomerization of CNK1 stimulates CNK1-mediated signaling in growth factor-stimulated cells. We identified Ser22 located within the SAM domain as AKT-dependent phosphorylation site triggering CNK1 oligomerization. Oligomeric CNK1 increased the affinity for active AKT indicating a positive AKT feedback mechanism. A CNK1 mutant lacking the SAM domain and the phosphorylation-defective mutant CNK1S22Aantagonizes oligomerization and prevents CNK1-driven cell proliferation and matrix metalloproteinase 14 promoter activation. The phosphomimetic mutant CNK1S22Dconstitutively oligomerizes and stimulates CNK1 downstream signaling. Searching the COSMIC database revealed Ser22 as putative target for oncogenic activation of CNK1. Like the phosphomimetic mutant CNK1S22D, the oncogenic mutant CNK1S22Fforms clusters in serum-starved cells comparable to clusters of CNK1 in growth factor-stimulated cells. CNK1 clusters induced by activating Ser22 mutants correlate with enhanced cell invasion and binding to and activation of ADP ribosylation factor 1 associated with tumor formation. Mutational analysis indicate that EGF-triggered phosphorylation of Thr8 within the SAM domain prevents AKT binding and antagonizes CNK1-mediated AKT signaling. Our findings reveal SAM domain-dependent oligomerization by AKT as switch for CNK1 activation.
authors: Department of Biochemistry and Synthetic Biology, Faculty of Biology, University of Freiburg, Schänzlestr. 18, 79104 Freiburg, Germany; Department of Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany; BIOSS - Centre for Biological Signalling Studies, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany. Electronic address: adrian.fischer@biologie.uni-freiburg.de.
authors: Adrian
authors: A
authors: Fischer
authors: Department of Biochemistry and Synthetic Biology, Faculty of Biology, University of Freiburg, Schänzlestr. 18, 79104 Freiburg, Germany; Department of Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany. Electronic address: wilfried.weber@biologie.uni-freiburg.de.
authors: Wilfried
authors: W
authors: Weber
authors: Department of Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany; BIOSS - Centre for Biological Signalling Studies, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany. Electronic address: bettina.warscheid@biologie.uni-freiburg.de.
authors: Bettina
authors: B
authors: Warscheid
authors: Department of Biochemistry and Synthetic Biology, Faculty of Biology, University of Freiburg, Schänzlestr. 18, 79104 Freiburg, Germany; Department of Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany; BIOSS - Centre for Biological Signalling Studies, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany. Electronic address: gerald.radziwill@bioss.uni-freiburg.de.
authors: Gerald
authors: G
authors: Radziwill
mesh_terms: D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D030541:Databases, Genetic; D025461:Feedback, Physiological; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D053511:Matrix Metalloproteinase 14 / Q000235:genetics / Q000378:metabolism; D018716:Molecular Mimicry; D009154:Mutation; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D055503:Protein Multimerization; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D000071682:Sterile Alpha Motif
chemical_list: C500833:CNKSR1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D051057:Proto-Oncogene Proteins c-akt; C507086:MMP14 protein, human; D053511:Matrix Metalloproteinase 14
keywords: Oligomerization; Oncogene; Scaffold protein; Signaling