scholarly journals Protein Kinase A Regulates MYC Protein through Transcriptional and Post-translational Mechanisms in a Catalytic Subunit Isoform-specific Manner

2013 ◽  
Vol 288 (20) ◽  
pp. 14158-14169 ◽  
Author(s):  
Achuth Padmanabhan ◽  
Xiang Li ◽  
Charles J. Bieberich
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Term Effect ◽  
Catalytic Subunit ◽  
Short Term ◽  
Catalytic Subunits ◽  
Multiple Substrates ◽  
Pka Catalytic Subunit ◽  
Kinase A ◽  
In Cells

MYC levels are tightly regulated in cells, and deregulation is associated with many cancers. In this report, we describe the existence of a MYC-protein kinase A (PKA)-polo-like kinase 1 (PLK1) signaling loop in cells. We report that sequential MYC phosphorylation by PKA and PLK1 protects MYC from proteasome-mediated degradation. Interestingly, short term pan-PKA inhibition diminishes MYC level, whereas prolonged PKA catalytic subunit α (PKACα) knockdown, but not PKA catalytic subunit β (PKACβ) knockdown, increases MYC. We show that the short term effect of pan-PKA inhibition on MYC is post-translational and the PKACα-specific long term effect on MYC is transcriptional. These data also reveal distinct functional roles among PKA catalytic isoforms in MYC regulation. We attribute this effect to differential phosphorylation selectivity among PKA catalytic subunits, which we demonstrate for multiple substrates. Further, we also show that MYC up-regulates PKACβ, transcriptionally forming a proximate positive feedback loop. These results establish PKA as a regulator of MYC and highlight the distinct biological roles of the different PKA catalytic subunits.

scholarly journals Activity, expression and function of a second Drosophila protein kinase A catalytic subunit gene.

Genetics ◽  
1995 ◽  
Vol 141 (4) ◽  
pp. 1507-1520 ◽  
Author(s):  
A Meléndez ◽  
W Li ◽  
D Kalderon
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Essential Gene ◽  
Sequence Similarity ◽  
Catalytic Subunit ◽  
Subunit Gene ◽  
Drosophila Protein ◽  
Pka Catalytic Subunit ◽  
Kinase A

Abstract The DC2 gene was isolated previously on the basis of sequence similarity to DC0, the major Drosophila protein kinase A (PKA) catalytic subunit gene. We show here that the 67-kD Drosophila DC2 protein behaves as a PKA catalytic subunit in vitro. DC2 is transcribed in mesodermal anlagen of early embryos. This expression depends on dorsal but on neither twist nor snail activity. DC2 transcriptional fusions mimic this embryonic expression and are also expressed in subsets of cells in the optic lamina, wing disc and leg discs of third instar larvae. A saturation screen of a small deficiency interval containing DC2 for recessive lethal mutations yielded no DC2 alleles. We therefore isolated new deficiencies to generate deficiency trans-heterozygotes that lacked DC2 activity. These animals were viable and fertile. The absence of DC2 did not affect the viability or phenotype of imaginal disc cells lacking DC0 activity or embryonic hatching of animals with reduced DC0 activity. Furthermore, transgenes expressing DC2 from a DC0 promoter did not efficiently rescue a variety of DC0 mutant phenotypes. These observations indicate that DC2 is not an essential gene and is unlikely to be functionally redundant with DC0, which has multiple unique functions during development.

scholarly journals A tripartite cooperative mechanism confers resistance of the protein kinase A catalytic subunit to dephosphorylation

2020 ◽  
Vol 295 (10) ◽  
pp. 3316-3329
Author(s):  
Tung O. Chan ◽  
Roger S. Armen ◽  
Santosh Yadav ◽  
Sushrut Shah ◽  
Jin Zhang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Catalytic Subunit ◽  
Site Directed Mutagenesis ◽  
Airway Smooth Muscle Cells ◽  
Activation Loop ◽  
Allosteric Sites ◽  
And Migration ◽  
Kinase A ◽  
In Cells

Phosphorylation of specific residues in the activation loops of AGC kinase group (protein kinase A, G, and C families) is required for activity of most of these kinases, including the catalytic subunit of PKA (PKAc). Although many phosphorylated AGC kinases are sensitive to phosphatase-mediated dephosphorylation, the PKAc activation loop uniquely resists dephosphorylation, rendering it “constitutively” phosphorylated in cells. Previous biophysical experiments and structural modeling have suggested that the N-terminal myristoylation signal and the C-terminal FXXF motif in PKAc regulate its thermal stability and catalysis. Here, using site-directed mutagenesis, molecular modeling, and in cell-free and cell-based systems, we demonstrate that substitutions of either the PKAc myristoylation signal or the FXXF motif only modestly reduce phosphorylation and fail to affect PKAc function in cells. However, we observed that these two sites cooperate with an N-terminal FXXW motif to cooperatively establish phosphatase resistance of PKAc while not affecting kinase-dependent phosphorylation of the activation loop. We noted that this tripartite cooperative mechanism of phosphatase resistance is functionally relevant, as demonstrated by changes in morphology, adhesion, and migration of human airway smooth muscle cells transfected with PKAc variants containing amino acid substitutions in these three sites. These findings establish that three allosteric sites located at the PKAc N and C termini coordinately regulate the phosphatase sensitivity of this enzyme. This cooperative mechanism of phosphatase resistance of AGC kinase opens new perspectives toward therapeutic manipulation of kinase signaling in disease.

scholarly journals c-MYC activates protein kinase A (PKA) by direct transcriptional activation of the PKA catalytic subunit beta (PKA-Cβ) gene

Oncogene ◽  
2002 ◽  
Vol 21 (51) ◽  
pp. 7872-7882 ◽  
Author(s):  
Kou-Juey Wu ◽  
Michela Mattioli ◽  
Herbert C Morse ◽  
Riccardo Dalla-Favera
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Transcriptional Activation ◽  
Catalytic Subunit ◽  
Pka Catalytic Subunit ◽  
Kinase A

Structure and function of the human sperm-specific isoform of protein kinase A (PKA) catalytic subunit Cα2

2012 ◽  
Vol 178 (3) ◽  
pp. 300-310 ◽  
Author(s):  
Tuva H. Hereng ◽  
Paul H. Backe ◽  
Jan Kahmann ◽  
Christoph Scheich ◽  
Magnar Bjørås ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Human Sperm ◽  
Structure And Function ◽  
Catalytic Subunit ◽  
And Function ◽  
Pka Catalytic Subunit ◽  
Kinase A

cAMP increases liver Na+-taurocholate cotransport by translocating transporter to plasma membranes

1997 ◽  
Vol 273 (4) ◽  
pp. G842-G848 ◽  
Author(s):  
Sunil Mukhopadhayay ◽  
M. Ananthanarayanan ◽  
Bruno Stieger ◽  
Peter J. Meier ◽  
Frederick J. Suchy ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Fusion Protein ◽  
Protein Kinase A ◽  
Plasma Membranes ◽  
Membrane Vesicles ◽  
Rat Hepatocytes ◽  
Plasma Membrane Vesicles ◽  
Short Term ◽  
Kinase A

Adenosine 3′,5′-cyclic monophosphate (cAMP), acting via protein kinase A, increases transport maximum of Na+-taurocholate cotransport within 15 min in hepatocytes (S. Grüne, L. R. Engelking, and M. S. Anwer. J. Biol. Chem. 268: 17734–17741, 1993); the mechanism of this short-term stimulation was investigated. Cycloheximide inhibited neither basal nor cAMP-induced increases in taurocholate uptake in rat hepatocytes, indicating that cAMP does not stimulate transporter synthesis. Studies in plasma membrane vesicles showed that taurocholate uptake was not stimulated by the catalytic subunit of protein kinase A but was higher when hepatocytes were pretreated with cAMP. Immunoblot studies with anti-fusion protein antibodies to the cloned Na+-taurocholate cotransport polypeptide (Ntcp) showed that pretreatment of hepatocytes with cAMP increased Ntcp content in plasma membranes but not in homogenates. Ntcp was detected in microsomes, endosomes, and Golgi fractions, and cAMP pretreatment resulted in a decrease only in endosomal Ntcp content. It is proposed that cAMP increases transport maximum of Na+-taurocholate cotransport, at least in part, by translocating Ntcp from endosomes to plasma membranes.

scholarly journals Protein Kinase A Catalytic Subunit Primed for Action: Time-Lapse Crystallography of Michaelis Complex Formation

Structure ◽  
2015 ◽  
Vol 23 (12) ◽  
pp. 2331-2340 ◽  
Author(s):  
Amit Das ◽  
Oksana Gerlits ◽  
Jerry M. Parks ◽  
Paul Langan ◽  
Andrey Kovalevsky ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Complex Formation ◽  
Protein Kinase A ◽  
Time Lapse ◽  
Catalytic Subunit ◽  
Action Time ◽  
Kinase A

scholarly journals Two PKA RIα holoenzyme states define ATP as an isoform-specific orthosteric inhibitor that competes with the allosteric activator, cAMP

2019 ◽  
Vol 116 (33) ◽  
pp. 16347-16356 ◽  
Author(s):  
Tsan-Wen Lu ◽  
Jian Wu ◽  
Phillip C. Aoto ◽  
Jui-Hung Weng ◽  
Lalima G. Ahuja ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Cross Talk ◽  
Structural Diversity ◽  
Dimer Interface ◽  
Biochemical Studies ◽  
Allosteric Mechanisms ◽  
Allosteric Activator ◽  
Kinase A ◽  
In Cells

Protein kinase A (PKA) holoenzyme, comprised of a cAMP-binding regulatory (R)-subunit dimer and 2 catalytic (C)-subunits, is the master switch for cAMP-mediated signaling. Of the 4 R-subunits (RIα, RIβ, RIIα, RIIβ), RIα is most essential for regulating PKA activity in cells. Our 2 RIα2C2 holoenzyme states, which show different conformations with and without ATP, reveal how ATP/Mg2+ functions as a negative orthosteric modulator. Biochemical studies demonstrate how the removal of ATP primes the holoenzyme for cAMP-mediated activation. The opposing competition between ATP/cAMP is unique to RIα. In RIIβ, ATP serves as a substrate and facilitates cAMP-activation. The isoform-specific RI-holoenzyme dimer interface mediated by N3A–N3A′ motifs defines multidomain cross-talk and an allosteric network that creates competing roles for ATP and cAMP. Comparisons to the RIIβ holoenzyme demonstrate isoform-specific holoenzyme interfaces and highlights distinct allosteric mechanisms for activation in addition to the structural diversity of the isoforms.

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