title: Characterization of protein kinase C theta activation loop autophosphorylation and the kinase domain catalytic mechanism.
abstract: Protein kinase C theta (PKCtheta), a member of the Ca(2+)-independent novel subfamily of PKCs, is required for T-cell receptor (TCR) signaling and IL2 production. PKCtheta-deficient mice have impaired Th2 responses in a murine ova-induced asthma model, while Th1 responses are normal. As an essential component of the TCR signaling complex, PKCtheta is a unique T-cell therapeutic target in the specific treatment of T-cell-mediated diseases. We report here the PKCtheta autophosphorylation characteristics and elucidation of the catalytic mechanism of the PKCtheta kinase domain using steady-state kinetics. Key phosphorylated residues of the active PKCtheta kinase domain expressed in Escherichia coli were characterized, and mutational analysis of the kinase domain was performed to establish the autophosphorylation and kinase activity relationships. Initial velocity, product inhibition, and dead-end inhibition studies provided assignments of the kinetic mechanism of PCKtheta(362)(-)(706) as ordered, wherein ATP binds kinase first and ADP is released last. Effects of solvent viscosity and ATPgammaS on PKCtheta catalysis demonstrated product release is partially rate limiting. Our studies provide important mechanistic insights into kinase activity and phosphorylation-mediated regulation of the novel PKC isoform, PKCtheta. These results should aid the design and discovery of PKCtheta antagonists as therapeutics for modulating T-cell-mediated immune and respiratory diseases.
authors: Department of Chemical and Screening Sciences, Wyeth Research, 87 Cambridge Park Drive, Cambridge, Massachusetts 02140, USA.
authors: Robert
authors: R
authors: Czerwinski
authors: Ann
authors: A
authors: Aulabaugh
authors: Rita M
authors: RM
authors: Greco
authors: Stephane
authors: S
authors: Olland
authors: Karl
authors: K
authors: Malakian
authors: Scott
authors: S
authors: Wolfrom
authors: Laura
authors: L
authors: Lin
authors: Ron
authors: R
authors: Kriz
authors: Mark
authors: M
authors: Stahl
authors: Ying
authors: Y
authors: Huang
authors: Lin
authors: L
authors: Liu
authors: Divya
authors: D
authors: Chaudhary
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001667:Binding, Competitive; D002384:Catalysis; D020134:Catalytic Domain / Q000235:genetics; D004789:Enzyme Activation; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009994:Osmolar Concentration; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity; D013912:Threonine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D010750:Phosphoproteins; D011994:Recombinant Proteins; D013912:Threonine; D012694:Serine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta