title: Cotranslational cis-phosphorylation of the COOH-terminal tail is a key priming step in the maturation of cAMP-dependent protein kinase.
abstract: cAMP-dependent protein kinase A (PKA), ubiquitously expressed in mammalian cells, regulates a plethora of cellular processes through its ability to phosphorylate many protein substrates, including transcription factors, ion channels, apoptotic proteins, transporters, and metabolic enzymes. The PKA catalytic subunit has two phosphorylation sites, a well-studied site in the activation loop (Thr(197)) and another site in the C-terminal tail (Ser(338)) for which the role of phosphorylation is unknown. We show here, using in vitro studies and experiments with S49 lymphoma cells, that cis-autophosphorylation of Ser(338) occurs cotranslationally, when PKA is associated with ribosomes and precedes posttranslational phosphorylation of the activation loop Thr(197). Ser(338) phoshorylation is not required for PKA activity or formation of the holoenzyme complex; however, it is critical for processing and maturation of PKA, and it is a prerequisite for phosphorylation of Thr(197). After Thr(197) and Ser(338) are phosphorylated, both sites are remarkably resistant to phosphatases. Phosphatase resistance of the activation loop, a unique feature of both PKA and PKG, reflects the distinct way that signal transduction dynamics are controlled by cyclic nucleotide-dependent PKs.
authors.affiliation: Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA.
authors.forename: Malik M
authors.initials: MM
authors.lastname: Keshwani
authors.forename: Christian
authors.initials: C
authors.lastname: Klammt
authors.forename: Sventja
authors.initials: S
authors.lastname: von Daake
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Ma
authors.forename: Alexandr P
authors.initials: AP
authors.lastname: Kornev
authors.forename: Senyon
authors.initials: S
authors.lastname: Choe
authors.forename: Paul A
authors.initials: PA
authors.lastname: Insel
authors.forename: Susan S
authors.initials: SS
authors.lastname: Taylor
mesh_terms: D000818:Animals; D020134:Catalytic Domain / Q000502:physiology*; D045744:Cell Line, Tumor; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000502:physiology*
chemical_list: D017868:Cyclic AMP-Dependent Protein Kinases