title: Differential tyrosine phosphorylation controls the function of CNK1 as a molecular switch in signal transduction.
abstract: Scaffold proteins are multidomain proteins without enzymatic function that play a central role in coordinating signaling processes. The scaffold protein CNK1 interacts with pathway-specific signaling proteins and thereby regulates these respective pathways. Here, we revealed tyrosine phosphorylation as a critical regulation mechanism to control the function of CNK1. We identified Tyr 26 as a PDGF-induced and, additionally, Tyr 519 and Tyr 665 as SRC-induced tyrosine phosphorylation sites. Phosphomimetic mutants indicate that phosphorylation of Tyr 519 recruits CNK1 to the nucleus and additional phosphorylation of Tyr 26 enables CNK1 to promote SRE-dependent gene expression. Contrary, mutants preventing tyrosine phosphorylation promote matrix metalloproteinase MMP14 promoter activity. CNK1-driven cell proliferation partially depends on its tyrosine phosphorylation. Upon PDGF stimulation, CNK1 is recruited to the plasma membrane mediated by SRC. Knock down of CNK1 prevents PDGF-induced SRE-dependent gene expression, MMP14 promoter activity and cell proliferation. Thus, tyrosine phosphorylation is an important mechanism to control the subcellular localization of CNK1 and its distinct biological functions.
authors: Faculty of Biology, Department of Biochemistry and Functional Proteomics, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany. Electronic address: fischer.adrian@yahoo.de.
authors: Adrian
authors: A
authors: Fischer
authors: BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany; Institute of Molecular Medicine and Cell Research (IMMZ), University of Freiburg, Stefan-Meier-Str. 17, 79104 Freiburg, Germany. Electronic address: tilman.brummer@zbsa.de.
authors: Tilman
authors: T
authors: Brummer
authors: Faculty of Biology, Department of Biochemistry and Functional Proteomics, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany. Electronic address: bettina.warscheid@biologie.uni-freiburg.de.
authors: Bettina
authors: B
authors: Warscheid
authors: Faculty of Biology, Department of Biochemistry and Functional Proteomics, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schaenzlestr. 1, 79104 Freiburg, Germany. Electronic address: gerald.radziwill@bioss.uni-freiburg.de.
authors: Gerald
authors: G
authors: Radziwill
mesh_terms: D002462:Cell Membrane / Q000201:enzymology / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D053511:Matrix Metalloproteinase 14 / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation; D010766:Phosphorylation / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: C500833:CNKSR1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D014443:Tyrosine; D019061:src-Family Kinases; C507086:MMP14 protein, human; D053511:Matrix Metalloproteinase 14
keywords: CNK1; Platelet-derived growth factor; SRC; Scaffold protein; Signal transduction; Tyrosine phosphorylation