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Engineering a bioluminescent indicator for cyclic AMP-dependent protein kinase.

ABSTRACT: cDNA coding for the luciferase in the firefly Photinus pyralis was amplified in vitro to generate cyclic AMP-dependent protein kinase phosphorylation sites. The DNA was transcribed and translated to generate light-emitting protein. A valine at position 217 was mutated to arginine to generate a site RRFS and the heptapeptide kemptide, the phosphorylation site of the porcine pyruvate kinase, was added at the N- or C-terminus of the luciferase. The proteins carrying phosphorylation sites were characterized for their specific activity, pI, effect of pH on the colour of the light emitted and effect of the catalytic subunit of protein kinase A in the presence of ATP. Only one of the recombinant proteins (RRFS) was significantly different from wild-type luciferase. The RRFS mutant had a lower specific activity, lower pH optimum, emitted greener light at low pH and when phosphorylated it decreased its activity by up to 80%. This latter effect was reversed by phosphatase. This recombinant protein is a good candidate to measure for the first time cyclic AMP-dependent phosphorylation in live cells.

SUBMITTER: Sala-Newby GB

PROVIDER: S-EPMC1151506 | biostudies-other | 1991 Nov

REPOSITORIES: biostudies-other

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Fyn Regulates Binding Partners of Cyclic-AMP Dependent Protein Kinase A.

Project description:The cAMP-dependent protein kinase A (PKA) is a serine/threonine kinase involved in many fundamental cellular processes, including migration and proliferation. Recently, we found that the Src family kinase Fyn phosphorylates the catalytic subunit of PKA (PKA-C) at Y69, thereby increasing PKA kinase activity. We also showed that Fyn induced the phosphorylation of cellular proteins within the PKA preferred target motif. This led to the hypothesis that Fyn could affect proteins in complex with PKA. To test this, we employed a quantitative mass spectrometry approach to identify Fyn-dependent binding partners in complex with PKA-C. We found Fyn enhanced the binding of PKA-C to several cytoskeletal regulators that localize to the centrosome and Golgi apparatus. Three of these Fyn-induced PKA interactors, AKAP9, PDE4DIP, and CDK5RAP2, were validated biochemically and were shown to exist in complex with Fyn and PKA in a glioblastoma cell line. Intriguingly, the complexes formed between PKA-C and these known AKAPs were dependent upon Fyn catalytic activity and expression levels. In addition, we identified Fyn-regulated phosphorylation sites on proteins in complex with PKA-C. We also identified and biochemically validated a novel PKA-C interactor, LARP4, which complexed with PKA in the absence of Fyn. These results demonstrate the ability of Fyn to influence the docking of PKA to specific cellular scaffolds and suggest that Fyn may affect the downstream substrates targeted by PKA.

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Cyclic AMP-dependent protein kinase controls virulence of the fungal pathogen Cryptococcus neoformans.

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Cyclic-AMP-dependent protein kinase A regulates apoptosis by stabilizing the BH3-only protein Bim.

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Negative regulation of histone deacetylase 8 activity by cyclic AMP-dependent protein kinase A.

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Project description:Neurofilament preparations isolated from bovine spinal cord contain cyclic-AMP-dependent protein kinase (PKA) activity. Treatment of this preparation with cyclic AMP, to dissociate the regulatory subunit of the kinase from the catalytic subunit, resulted in retention of the kinase activity but loss of cyclic AMP regulation. This suggests that PKA is associated via its catalytic subunit with the neurofilament preparation. The association of exogenous PKA from bovine heart with the neurofilament preparation and with neurofilaments reconstituted from purified neurofilament proteins was also investigated. Either the free catalytic subunit or combinations of the catalytic and regulatory subunits of PKA were incubated with the preparations, and the degree of association was determined as the level of kinase activity that co-sediments with neurofilaments. The results indicate that the free catalytic subunit of PKA co-sediments with neurofilaments reconstituted from purified proteins. The regulatory subunit of PKA from bovine heart, when pre-mixed with the catalytic subunit, decreased the level of kinase that co-sediments with the neurofilament fraction in a dose-dependent manner. This effect of the regulatory subunit was reversed by inclusion of cyclic AMP in the incubation medium before centrifugation. The above findings suggest that the regulatory subunit, when attached to the catalytic subunit, has an inhibitory effect on its association with neurofilaments, with the implication that the association may be a cyclic-AMP-regulated event.

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The cyclic AMP-dependent protein kinase a network regulates development and virulence in Aspergillus fumigatus.

Project description:Aspergillus fumigatus is an important pathogen of immunocompromised hosts, causing pneumonia and invasive disseminated disease with high mortality. To determine the importance of the cyclic AMP (cAMP) signaling pathway for virulence, the pkaC1 gene encoding a protein kinase A (PKA) catalytic subunit was cloned and characterized. Deletion of pkaC1 led to reduced conidiation and growth. PKA activity was not detectable in DeltapkaC1, DeltagpaB, and DeltaacyA mutant strains. gpaB and acyA encode a G protein alpha subunit involved in cAMP signal transduction and adenylate cyclase, respectively. Addition of cAMP led to PKA activity in crude extracts of both the DeltagpaB and DeltaacyA strains but not in crude extracts of the DeltapkaC1 strain. These findings provide evidence that PKAC1 represents the predominant form of PKA under the conditions tested, and GPAB and ACYA are members of the cAMP signaling cascade. Analysis of a pksPp-lacZ gene fusion indicated that the expression of the pathogenicity determinant-encoding pksP gene was reduced in DeltapkaC1 mutant strains compared with the expression of the gene fusion in the parental strain. In a low-dose murine inhalation model, conidia of both the DeltapkaC1 and DeltagpaB mutant strains were almost avirulent. Taken together, these findings indicate that the cAMP-PKA signal transduction pathway is required for A. fumigatus pathogenicity.

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Cyclic AMP- and (Rp)-cAMPS-induced conformational changes in a complex of the catalytic and regulatory (RI{alpha}) subunits of cyclic AMP-dependent protein kinase.

Project description:We took a discovery approach to explore the actions of cAMP and two of its analogs, one a cAMP mimic ((S(p))-adenosine cyclic 3':5'-monophosphorothioate ((S(p))-cAMPS)) and the other a diastereoisomeric antagonist ((R(p))-cAMPS), on a model system of the type I? cyclic AMP-dependent protein kinase holoenzyme, RI?(91-244)·C-subunit, by using fluorescence spectroscopy and amide H/(2)H exchange mass spectrometry. Specifically, for the fluorescence experiments, fluorescein maleimide was conjugated to three cysteine single residue substitution mutants, R92C, T104C, and R239C, of RI?(91-244), and the effects of cAMP, (S(p))-cAMPS, and (R(p))-cAMPS on the kinetics of R-C binding and the time-resolved anisotropy of the reporter group at each conjugation site were measured. For the amide exchange experiments, ESI-TOF mass spectrometry with pepsin proteolytic fragmentation was used to assess the effects of (R(p))-cAMPS on amide exchange of the RI?(91-244)·C-subunit complex. We found that cAMP and its mimic perturbed at least parts of the C-subunit interaction Sites 2 and 3 but probably not Site 1 via reduced interactions of the linker region and ?C of RI?(91-244). Surprisingly, (R(p))-cAMPS not only increased the affinity of RI?(91-244) toward the C-subunit by 5-fold but also produced long range effects that propagated through both the C- and R-subunits to produce limited unfolding and/or enhanced conformational flexibility. This combination of effects is consistent with (R(p))-cAMPS acting by enhancing the internal entropy of the R·C complex. Finally, the (R(p))-cAMPS-induced increase in affinity of RI?(91-244) toward the C-subunit indicates that (R(p))-cAMPS is better described as an inverse agonist because it decreases the fractional dissociation of the cyclic AMP-dependent protein kinase holoenzyme and in turn its basal activity.

| S-EPMC2957725 | biostudies-literature

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