title: Subcellular localization and biological actions of activated RSK1 are determined by its interactions with subunits of cyclic AMP-dependent protein kinase.
abstract: Cyclic AMP (cAMP)-dependent protein kinase (PKA) and ribosomal S6 kinase 1 (RSK1) share several cellular proteins as substrates. However, to date no other similarities between the two kinases or interactions between them have been reported. Here, we describe novel interactions between subunits of PKA and RSK1 that are dependent upon the activation state of RSK1 and determine its subcellular distribution and biological actions. Inactive RSK1 interacts with the type I regulatory subunit (RI) of PKA. Conversely, active RSK1 interacts with the catalytic subunit of PKA (PKAc). Binding of RSK1 to RI decreases the interactions between RI and PKAc, while the binding of active RSK1 to PKAc increases interactions between PKAc and RI and decreases the ability of cAMP to stimulate PKA. The RSK1/PKA subunit interactions ensure the colocalization of RSK1 with A-kinase PKA anchoring proteins (AKAPs). Disruption of the interactions between PKA and AKAPs decreases the nuclear accumulation of active RSK1 and, thus, increases its cytosolic content. This subcellular redistribution of active RSK1 is manifested by increased phosphorylation of its cytosolic substrates tuberous sclerosis complex 2 and BAD by epidermal growth factor along with decreased cellular apoptosis.
authors.affiliation: Department of Pharmacology, Loyola University Chicago, Stritch School of Medicine, 2160 South First Avenue, Maywood, IL 60153, USA.
authors.forename: Deepti
authors.initials: D
authors.lastname: Chaturvedi
authors.forename: Helen M
authors.initials: HM
authors.lastname: Poppleton
authors.forename: Teresa
authors.initials: T
authors.lastname: Stringfield
authors.forename: Ann
authors.initials: A
authors.lastname: Barbier
authors.forename: Tarun B
authors.initials: TB
authors.lastname: Patel
mesh_terms: D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology; D000242:Cyclic AMP / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D046912:Multiprotein Complexes; D010766:Phosphorylation; D011485:Protein Binding; D021122:Protein Subunits; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D054758:A Kinase Anchor Proteins; C105137:AKAP1 protein, human; D048868:Adaptor Proteins, Signal Transducing; C486333:Akap1 protein, mouse; D046912:Multiprotein Complexes; D021122:Protein Subunits; D004815:Epidermal Growth Factor; D000242:Cyclic AMP; C069329:RPS6KA1 protein, human; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C512964:Rps6ka1 protein, mouse; D017868:Cyclic AMP-Dependent Protein Kinases