title: Dual specificity A-kinase anchoring proteins (AKAPs) contain an additional binding region that enhances targeting of protein kinase A type I.
abstract: A-kinase anchoring proteins (AKAPs) target protein kinase A (PKA) to a variety of subcellular locations. Conventional AKAPs contain a 14-18-amino acid sequence that forms an amphipathic helix that binds with high affinity to the regulatory (R) subunit of PKA type II. More recently, a group of dual specificity AKAPs has been classified on the basis of their ability to bind the PKA type I and the PKA type II isozymes. In this study we show that dual specificity AKAPs contain an additional PKA binding determinant called the RI Specifier Region (RISR). A variety of protein interaction assays and immunoprecipitation and immunolocalization experiments indicates that the RISR augments RI binding in vitro and inside cells. Cellular delivery of the RISR peptide uncouples RI anchoring to Ezrin leading to release of T cell inhibition by cAMP. Likewise, expression of mutant Ezrin forms where RI binding has been abrogated by substitution of the RISR sequence prevents cAMP-mediated inhibition of T cell function. Thus, we propose that the RISR acts in synergy with the amphipathic helix in dual specificity anchoring proteins to enhance anchoring of PKA type I.
authors.affiliation: Biotechnology Centre of Oslo, Nordic EMBL Partnership, University of Oslo, P. O. Box 1125 Blindern, N-0317 Oslo, Norway.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Jarnaess
authors.forename: Anja
authors.initials: A
authors.lastname: Ruppelt
authors.forename: Anne Jorunn
authors.initials: AJ
authors.lastname: Stokka
authors.forename: Birgitte
authors.initials: B
authors.lastname: Lygren
authors.forename: John D
authors.initials: JD
authors.lastname: Scott
authors.forename: Kjetil
authors.initials: K
authors.lastname: Taskén
mesh_terms: D054758:A Kinase Anchor Proteins / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism; D054743:Cyclic AMP-Dependent Protein Kinase Type I / Q000235:genetics / Q000378:metabolism*; D054746:Cyclic AMP-Dependent Protein Kinase Type II / Q000235:genetics / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D017433:Protein Structure, Secondary / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D013601:T-Lymphocytes / Q000166:cytology / Q000201:enzymology*; D000099149:Ezrin
chemical_list: D054758:A Kinase Anchor Proteins; D000242:Cyclic AMP; D054743:Cyclic AMP-Dependent Protein Kinase Type I; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D003598:Cytoskeletal Proteins; D000099149:Ezrin