title: G protein-coupled receptor kinase 5 phosphorylates nucleophosmin and regulates cell sensitivity to polo-like kinase 1 inhibition.
abstract: G protein-coupled receptor kinases (GRKs) phosphorylate activated G protein-coupled receptors, leading to their desensitization and endocytosis. GRKs have also been implicated in phosphorylating other classes of proteins and can localize in a variety of cellular compartments, including the nucleus. Here, we attempted to identify potential nuclear substrates for GRK5. Our studies reveal that GRK5 is able to interact with and phosphorylate nucleophosmin (NPM1) both in vitro and in intact cells. NPM1 is a nuclear protein that regulates a variety of cell functions including centrosomal duplication, cell cycle control, and apoptosis. GRK5 interaction with NPM1 is mediated by the N-terminal domain of each protein, and GRK5 primarily phosphorylates NPM1 at Ser-4, a site shared with polo-like kinase 1 (PLK1). NPM1 phosphorylation by GRK5 and PLK1 correlates with the sensitivity of cells to undergo apoptosis with cells having higher GRK5 levels being less sensitive and cells with lower GRK5 being more sensitive to PLK1 inhibitor-induced apoptosis. Taken together, our results demonstrate that GRK5 phosphorylates Ser-4 in nucleophosmin and regulates the sensitivity of cells to PLK1 inhibition.
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Christopher H
authors.initials: CH
authors.lastname: So
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Allison M
authors.initials: AM
authors.lastname: Michal
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Rouzbeh
authors.initials: R
authors.lastname: Mashayekhi
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107. Electronic address: benovic@mail.jci.tju.edu.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Benovic
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D018385:Centrosome / Q000378:metabolism; D054774:G-Protein-Coupled Receptor Kinase 5 / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D000090243:Nucleophosmin; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D054774:G-Protein-Coupled Receptor Kinase 5; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1; C000716967:NPM1 protein, human; C517898:GRK5 protein, human