PEST sequences in cAMP-dependent protein kinase subunits of the aquatic fungus Blastocladiella emersonii are necessary for in vitro degradation by endogenous proteases

Oncoprotein 18 (Op18, also termed p19, 19K, metablastin, stathmin, and prosolin) is a recently identified regulator of microtubule (MT) dynamics. Op18 is a target for both cell cycle and cell surface receptor-coupled kinase systems, and phosphorylation of Op18 on specific combinations of sites has been shown to switch off its MT-destabilizing activity. Here we show that induced expression of the catalytic subunit of cAMP-dependent protein kinase (PKA) results in a dramatic increase in cellular MT polymer content concomitant with phosphorylation and partial degradation of Op18. That PKA may regulate the MT system by downregulation of Op18 activity was evaluated by a genetic system allowing conditional co-expression of PKA and a series of kinase target site–deficient mutants of Op18. The results show that phosphorylation of Op18 on two specific sites, Ser-16 and Ser-63, is necessary and sufficient for PKA to switch off Op18 activity in intact cells. The regulatory importance of dual phosphorylation on Ser-16 and Ser-63 of Op18 was reproduced by in vitro assays. These results suggest a simple model where PKA phosphorylation downregulates the MT-destabilizing activity of Op18, which in turn promotes increased tubulin polymerization. Hence, the present study shows that Op18 has the potential to regulate the MT system in response to external signals such as cAMP-linked agonists.

Download Full-text

Adrenocorticotrophic hormone stimulates phosphotyrosine phosphatase SHP2 in bovine adrenocortical cells: phosphorylation and activation by cAMP-dependent protein kinase

Biochemical Journal ◽

10.1042/bj3520483 ◽

2000 ◽

Vol 352 (2) ◽

pp. 483-490 ◽

Cited By ~ 25

Author(s):

Stéphane ROCCHI ◽

Isabelle GAILLARD ◽

Emmanuel VAN OBBERGHEN ◽

Edmond M. CHAMBAZ ◽

Isabelle VILGRAIN

Keyword(s):

Protein Kinase ◽

Kinase Assay ◽

Dependent Manner ◽

Adrenocorticotrophic Hormone ◽

Adrenocortical Cells ◽

Dependent Protein Kinase ◽

Phosphotyrosine Phosphatase ◽

Camp Dependent Protein Kinase ◽

Dependent Protein

During activation of adrenocortical cells by adrenocorticotrophic hormone (ACTH), tyrosine dephosphorylation of paxillin is stimulated and this correlates with protrusion of filopodial structures and a decreased number of focal adhesions. These effects are inhibited by Na3VO4, a phosphotyrosine phosphatase inhibitor [Vilgrain, Chinn, Gaillard, Chambaz and Feige (1998) Biochem. J. 332, 533–540]. However, the tyrosine phosphatases involved in these processes remain to be identified. In this study, we provide evidence that the Src homology domain (SH)2-containing phosphotyrosine phosphatase (SHP)2, but not SHP1, is expressed in adrenocortical cells and is phosphorylated upon ACTH challenge. ACTH (10-8M) treatment of 32P-labelled adrenocortical cells resulted in an increase in phosphorylated SHP2. By probing SHP2-containing immunoprecipitates with an antibody to phosphoserine we found that SHP2 was phosphorylated on serine in ACTH-treated cells in a dose- and time-dependent manner. Furthermore, using an in vitro kinase assay, we showed that SHP2 was a target for cAMP-dependent protein kinase (PKA). Serine was identified as the only target amino acid phosphorylated in SHP2. Phosphorylation of SHP2 by PKA resulted in a dramatic stimulation of phosphatase activity measured either with insulin receptor substrate-1 or with the synthetic peptide [32P]poly(Glu/Tyr) as substrate. In an in-gel assay of SHP2-containing immunoprecipitates, phosphorylated in vitro by PKA or isolated from adrenocortical cells treated with 10nM ACTH, a pronounced activation of SHP2 activity was shown. These observations clearly support the idea that a PKA-mediated signal transduction pathway contributes to SHP2 regulation in adrenocortical cells and point to SHP2 as a possible mediator of the effects of ACTH.

Download Full-text

cAMP-dependent protein kinase (PKA) complexes probed by complementary differential scanning fluorimetry and ion mobility–mass spectrometry

Biochemical Journal ◽

10.1042/bcj20160648 ◽

2016 ◽

Vol 473 (19) ◽

pp. 3159-3175 ◽

Cited By ~ 31

Author(s):

Dominic P. Byrne ◽

Matthias Vonderach ◽

Samantha Ferries ◽

Philip J. Brownridge ◽

Claire E. Eyers ◽

...

Keyword(s):

Mass Spectrometry ◽

Protein Kinase ◽

Ion Mobility ◽

Catalytic Domain ◽

Ion Mobility Mass Spectrometry ◽

Dependent Protein Kinase ◽

Camp Dependent Protein Kinase ◽

Differential Scanning Fluorimetry ◽

Dependent Protein

cAMP-dependent protein kinase (PKA) is an archetypal biological signaling module and a model for understanding the regulation of protein kinases. In the present study, we combine biochemistry with differential scanning fluorimetry (DSF) and ion mobility–mass spectrometry (IM–MS) to evaluate effects of phosphorylation and structure on the ligand binding, dynamics and stability of components of heteromeric PKA protein complexes in vitro. We uncover dynamic, conformationally distinct populations of the PKA catalytic subunit with distinct structural stability and susceptibility to the physiological protein inhibitor PKI. Native MS of reconstituted PKA R2C2 holoenzymes reveals variable subunit stoichiometry and holoenzyme ablation by PKI binding. Finally, we find that although a ‘kinase-dead’ PKA catalytic domain cannot bind to ATP in solution, it interacts with several prominent chemical kinase inhibitors. These data demonstrate the combined power of IM–MS and DSF to probe PKA dynamics and regulation, techniques that can be employed to evaluate other protein-ligand complexes, with broad implications for cellular signaling.

Download Full-text

cAMP-dependent protein kinase mediates hydrosmotic effect of vasopressin in collecting duct

AJP Cell Physiology ◽

10.1152/ajpcell.1992.263.1.c147 ◽

1992 ◽

Vol 263 (1) ◽

pp. C147-C153 ◽

Cited By ~ 24

Author(s):

H. M. Snyder ◽

T. D. Noland ◽

M. D. Breyer

Keyword(s):

Protein Kinase ◽

Protein Phosphorylation ◽

Water Permeability ◽

Collecting Duct ◽

Regulatory Subunit ◽

Dependent Protein Kinase ◽

Camp Dependent Protein Kinase ◽

Dependent Protein ◽

Pka Regulatory Subunit

The role of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA) in mediating the hydrosmotic effect of vasopressin in in vitro microperfused rabbit cortical collecting ducts (CCDs) was examined. We measured PKA substrate phosphorylation and water permeability [hydraulic conductivity (Lp) = 10(-7) cm.atm-1.s-1], stimulated by substituted cAMP analogues selective for a unique cAMP binding site (site A or B) on PKA regulatory subunit (R). Synergy between site A- and site B-selective analogues suggests involvement of PKA, because both sites must be occupied for R to dissociate from the catalytic subunit (C), allowing phosphorylation to proceed. As single agents, the site B-selective analogues 8-(4-chlorophenylthio)-cAMP (8-CPT) and 8-thiomethyl-cAMP (8-SCH3) were at least two orders of magnitude more potent than the site A-selective analogues N6-monobutyryl-cAMP (N6-mono) or N6-benzoyl-cAMP (N6-benz). Combinations of subthreshold concentrations of two site A analogues (N6-mono+N6-benz) or two site B-selective analogues (8-CPT + 8-SCH3) failed to significantly increase protein phosphorylation or water permeability. In contrast, combination of a site A plus site B analogue synergistically stimulated both protein phosphorylation and Lp. Rp-cAMPS, an inhibitor of cAMP binding to PKA, reduced both vasopressin (41% inhibition)- and cAMP (56% inhibition)-stimulated water permeability. H-89 (50 microM), an inhibitor of PKA kinase activity, also blocked cAMP-stimulated water permeability (90% inhibition). These findings suggest that vasopressin-induced water permeability in the rabbit CCD is mediated by PKA.

Download Full-text

Autophosphorylation and rapid dephosphorylation of the cAMP-dependent protein kinase from Blastocladiella emersonii zoospores.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)32320-2 ◽

1983 ◽

Vol 258 (11) ◽

pp. 6972-6978 ◽

Cited By ~ 2

Author(s):

S L Gomes ◽

M H Juliani ◽

J C da Costa Maia ◽

R Rangel-Aldao

Keyword(s):

Protein Kinase ◽

Dependent Protein Kinase ◽

Camp Dependent Protein Kinase ◽

Dependent Protein ◽

Blastocladiella Emersonii

Download Full-text

Dephosphorylation of cAMP-dependent protein kinase regulatory subunit in stimulated parietal cells

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1992.262.4.g763 ◽

1992 ◽

Vol 262 (4) ◽

pp. G763-G773 ◽

Cited By ~ 1

Author(s):

J. R. Goldenring ◽

V. A. Asher ◽

M. F. Barreuther ◽

J. J. Lewis ◽

S. M. Lohmann ◽

...

Keyword(s):

Protein Kinase ◽

Okadaic Acid ◽

Protein Phosphatase ◽

Parietal Cells ◽

Regulatory Subunit ◽

Dependent Protein Kinase ◽

Camp Dependent Protein Kinase ◽

Dependent Protein ◽

Endogenous Proteins

The phosphorylation of endogenous proteins was investigated in subcellular fractions prepared from isolated rabbit parietal cells incubated with either cimetidine (unstimulated) or a combination of histamine and forskolin (maximally stimulated). Phosphorylation of endogenous proteins in subfractions was then assessed in a post hoc assay using [gamma-32P]ATP as a phosphate donor in vitro. The Mg(2+)-dependent incorporation of [32P]phosphate into a 52-kDa protein (pp52M) was observed in the 4,000 g membrane fraction from stimulated but not unstimulated cells. The pp52M protein was identified as the type II regulatory subunit of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase (RII) by isoelectric focusing, comigration with cAMP-binding proteins, and immunoprecipitation. Incorporation of [32P]phosphate into RII in the in vitro assay in the presence of Zn2+ was apparent in the 4,000 g membrane from stimulated but not unstimulated cells. The results thus suggested that, on stimulation, RII in membrane was dephosphorylated. Incorporation of [32P]phosphate into membrane-associated RII was completely abolished in the presence of 10 microM cAMP. The decrease in RII phosphorylation in membrane from stimulated cells assayed in the presence of cAMP was due to a phosphoprotein phosphatase activity that was completely inhibited by okadaic acid (1 microM). The results indicate that stimulation of parietal cells with histamine and forskolin results in the dephosphorylation of membrane bound RII by a protein phosphatase that is also membrane associated. Furthermore, okadaic acid inhibited histamine-stimulated accumulation of [14C]aminopyrine into isolated parietal cells without altering stimulated increases in cAMP. Thus protein phosphatase may be a significant regulator of parietal cell function.

Download Full-text