Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies identified proline-directed protein kinase (PDPK) as a growth factor-sensitive serine/threonine protein kinase that is active in the cytosol of proliferative cells and tissues during interphase. In this communication, we report that the regulatory subunit (RII) of bovine cardiac muscle cAMP-dependent protein kinase (PKA) is a putative substrate for the multifunctional PDPK. Purified RII is readily phosphorylated by PDPK in vitro in a time-dependent, enzyme-dependent manner to a stoichiometry approaching 0.7 mol phosphate/mol RII subunit protein. The major RII phosphorylation site is identified as a threonine residue located within a large hydrophobic tryptic peptide that is predicted to contain the cAMP binding domains. In contrast to the reported effects of RII autophosphorylation, kinetic analysis of RII function following phosphorylation by PDPK indicates that the inhibitory potency of RII toward the catalytic subunit of PKA in a reassociation assay is increased in proportion to the degree of phosphorylation. Further studies indicate that the cAMP-dependent activation of the RII2C2 holoenzyme is inhibited by PDPK phosphorylation. Taken together, the results of these studies indicate that phosphorylation of RII by PDPK attenuates the activity of PKA. This antagonistic interaction suggests a biochemical mechanism by which a growth factor-activated signaling system may function to modulate cAMP-dependent cellular responses.
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PMID:Phosphorylation of RII subunit and attenuation of cAMP-dependent protein kinase activity by proline-directed protein kinase. 165 46

Casein kinase II (CKII) is a ubiquitous serine/threonine protein kinase with numerous key functions in cell metabolism and growth. The human CKII has a tetrameric structure; two catalytic subunits (alpha and alpha') form the holoenzyme together with two presumably regulatory subunits (beta). The gene encoding CKII subunit beta was isolated from human genomic DNA and analyzed for its primary structure using exclusively nonradioactive procedures. The gene was found to span 4.2 kilobase pairs and to be composed of seven exons. Exon sizes range from 76 (exon 5) to 329 base pairs (bp) (exon 1), intron sizes from 145 (intron V) to 965 bp (intron II). All exon-intron junctional sequences conform to the canonical GT-AG rule. Primer extension analysis determined three transcription initiation sites, at 951, 919, and (minor) 840 bp upstream of the translation start site. The translation start is located early in the second exon; exon 1 is untranslated. The 3'-cleavage/polyadenylation signal sequence (AA-TAAA) is in the last exon at position 4173 bp relative to the first transcription initiation site. The coding sequence for CKII beta comprises 648 nucleotides identical to the published CKII beta-cDNA sequence (Jakobi, R., Voss, H., and Pyerin, W. (1989) Eur. J. Biochem. 183, 227-233). The upstream promoter region of the CKII beta gene contains multiple potential gene regulatory sequence elements, noticeable DNA structures, and the characteristics of a housekeeping gene (more than one transcription initiation site, lack of a TATA-box, presence of a CpG island, occurrence of multiple GC boxes and of nonstandard positioned CCAAT boxes). The CKII beta gene promoter shares common features with that of mammalian protein kinases and is closely related to the regulatory subunit gene promoter of cAMP-dependent protein kinase.
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PMID:Structure of the gene encoding human casein kinase II subunit beta. 185 4

The inhibitory potencies of bioflavonoids on various tyrosine protein kinases and serine/threonine protein kinases were investigated. The phosphotransferase activity of an oncogene product, pp130fps, and a growth factor receptor, insulin receptor, were inhibited by myricetin, a derivative of quercetin. However, tyrosine kinase activity in the particulate fraction from human platelets (PM-TPK) was resistant to myricetin. Apparent Ki values of myricetin for tyrosine protein kinases of pp130fps and insulin receptor were 1.8 and 2.6 microM, respectively. The Ki values for serine/threonine kinase activities of myosin light chain kinase (MLC-kinase), casein kinase I, casein kinase II, cAMP-dependent protein kinase, and protein kinase C were 1.7 microM, 9.0 microM, 0.6 microM, 27.5 microM, and 12.1 microM, respectively. Lineweaver-Burk plots revealed that myricetin competitively inhibits pp130fps tyrosine kinase, myosin light chain kinase, casein kinase I and II with ATP, but does not inhibit other protein kinases. Since myricetin is a hydroxylated derivative of quercetin, the inhibitory effects of a series of seven flavonoids with various numbers of hydroxy residues were examined. Structure activity studies exhibited that the inhibitory potencies of the flavonoids for tyrosine kinases of pp130fps and insulin receptor correlated with the number of hydroxy residues on the flavone rings (gamma = 0.974 and 0.926, respectively), whereas the hydroxylation influenced to a lesser extent the inhibitory potencies for serine/threonine protein kinase. The hydroxy residues at position 3' and 5' did not affect the activities of cAMP-dependent protein kinase, and protein kinase C, and the hydroxylation at position 5' is detrimental for the inhibition of MLC-kinase, and casein kinase I and II. Thus, flavonoids may be useful tools to elucidate the active site of tyrosine and serine/threonine protein kinases.
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PMID:Differential effects of flavonoids as inhibitors of tyrosine protein kinases and serine/threonine protein kinases. 316 98

Protein kinase N (PKN) is a serine/threonine protein kinase rapidly activated by nerve growth factor (NGF) and other agents in various cell lines. The possible involvement of PKN in the multiple pathways of the NGF mechanism of action was previously established through the use of purine analogs, some of which are apparently specific inhibitors of this kinase. Since a PKN-like activity is modulated in several cell lines by cAMP analogs and this activation requires the activity of cAMP-dependent protein kinase, the aim of the present work is to investigate possible interactions between PKN and C-PKA. Pre-incubation of the two kinases in the presence of ATP leads to potentiated phosphorylation of histone HF1, Kemptide (a substrate for C-PKA, but not for PKN), and several additional substrates. This augmented phosphorylating activity is insensitive to 6-thioguanine (an inhibitor for PKN, but not for C-PKA) and is suppressed both by the Walsh inhibitor and by the regulatory subunit of PKA. PKN-pretreated C-PKA shows a significant decrease in Km for Kemptide and a substantial increase in Vmax. C-PKA and PKN are widely expressed enzymes and the possibility of PKN-dependent modulation of PKA in intact cells would therefore have biological implications for signal transduction mechanisms.
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PMID:Nerve growth factor-activated protein kinase N modulates the cAMP-dependent protein kinase. 771 18

Signal transduction for tumor necrosis factor-alpha and interleukin-1 involves sphingomyelin hydrolysis to ceramide and stimulation of a ceramide-activated serine/threonine protein kinase (Mathias, S., Younes, A., Kan, C., Orlow, I., Joseph, C., and Kolesnick, R. (1993) Science 259, 519-522). Kinase activity is detected by phosphorylation of a 19-amino acid peptide derived from the sequence surrounding Thr669 of the epidermal growth factor receptor. Thr669 is contained within a -Pro-Leu-Thr-Pro- motif, which conforms to a known recognition sequence for the proline-directed class of serine/threonine protein kinases. The present studies used peptides with single-site amino acid substitutions within this sequence to assess substrate recognition by ceramide-activated protein kinase. Substitution of alanine for the C-terminal but not the N-terminal proline reduced kinase activity by 80%. Similarly, substitution of basic residues for the leucine residue reduced kinase activity by 90%. Substitution of acidic residues for leucine, or its removal, also markedly reduced kinase activity. Surprisingly, addition of a leucine residue between threonine and the C-terminal proline enhanced kinase activity 3-4 fold. The Vmax(app) of the enzyme toward the control peptide containing -Pro-Leu-Thr-Pro- (200 +/- 11 pmol of peptide phosphorylated/min/mg of membrane protein) was enhanced 2.3-fold by ceramide. However, ceramide had no effect on the Km (2.0 +/- 0.4 mM). Membranes containing ceramide-activated protein kinase showed minimal activity toward peptides derived from substrates for casein kinase II, S6 kinase, protein kinase C, and cAMP-dependent protein kinase, but possessed substantial activity toward a calmodulin kinase substrate. However, activities toward these substrates were not enhanced by ceramide. These results suggest that ceramide-activated protein kinase may be a member of the proline-directed class of protein kinases and display specificity for -Leu-Thr-Pro- as a minimal substrate recognition motif.
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PMID:Substrate recognition by ceramide-activated protein kinase. Evidence that kinase activity is proline-directed. 837 61

Internalization of the urokinase-type plasminogen activator (uPA) requires two receptors, the uPA receptor (uPAR) and the low density lipoprotein receptor-related protein (LRP)/alpha2-macroglobulin (alpha2M) receptor. Here, we address whether protein kinases are involved in the internalization of uPA by human melanoma cells. Initially, we found that the internalization of uPA was significantly inhibited by the serine/threonine protein kinase inhibitors staurosporine, K-252a and H-89, but not by the tyrosine kinase inhibitors, genistein and lavendustin A. Internalization of uPA was also inhibited by a pseudosubstrate peptide for cAMP-dependent protein kinase (PKA), but not by a pseudosubstrate peptide for protein kinase C. We confirmed a requirement for PKA-activity and implicated a specific isoform by using an antisense oligonucleotide against the regulatory subunit RI alpha of PKA which suppresses PKA-I activity. Exposure of cells to this oligonucleotide led to a specific, dose-dependent decrease in RI alpha protein and to a significant inhibition in the rate of uPA internalization. We further demonstrate that treatment of melanoma cells with either H-89 or PKA RI alpha antisense oligonucleotides also resulted in a decreased internalization of two other ligands of LRP, activated alpha2M and lactoferrin, indicating that PKA activity is associated with LRP. Finally, we demonstrate that PKA activity is also required for the internalization of transferrin, but not for the internalization of the epidermal growth factor or adenovirus 2, suggesting that in melanoma cells, PKA activity is not generally required for clathrin-mediated endocytosis, but is rather associated with specific internalization receptors.
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PMID:Receptor-mediated endocytosis of urokinase-type plasminogen activator is regulated by cAMP-dependent protein kinase. 921 25

Peutz-Jeghers syndrome (PJS) is an autosomal dominant disease characterized by melanocytic macules, hamartomatous polyps and an increased risk for numerous cancers. The human LKB1 (hLKB1) gene encodes a serine/threonine protein kinase that is deficient in the majority of patients with PJS. The murine LKB1 (mLKB1) cDNA was isolated, sequenced and shown to produce a 2.4-kb transcript encoding a 436 amino acid protein with 90% identity with hLKB1. RNA blot and RNase-protection analysis revealed that mLKB1 mRNA is expressed in all tissues and cell lines examined. The widespread expression of LKB1 transcripts is consistent with the elevated risk of multiple cancer types in PJS patients. The predicted LKB1 protein sequence terminates with a conserved prenylation motif (Cys(433)-Lys-Gln-Gln(436)) directly downstream from a consensus cAMP-dependent protein kinase (PKA) phosphorylation site (Arg(428)-Arg-Leu-Ser(431)). The expression of enhanced green fluorescent protein (EGFP)-mLKB1 chimaeras demonstrated that LKB1 possesses a functional prenylation motif that is capable of targeting EGFP to cellular membranes. Mutation of Cys(433) to an alanine residue, but not phosphorylation by PKA, blocked membrane localization. These findings suggest that PKA does phosphorylate LKB1, although this phosphorylation does not alter the cellular localization of LKB1.
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PMID:LKB1, a novel serine/threonine protein kinase and potential tumour suppressor, is phosphorylated by cAMP-dependent protein kinase (PKA) and prenylated in vivo. 1064 27

The Arabidopsis thaliana SOS2 and SOS3 genes are required for intracellular Na(+) and K(+) homeostasis and plant tolerance to high Na(+) and low K(+) environments. SOS3 is an EF hand type calcium-binding protein having sequence similarities with animal neuronal calcium sensors and the yeast calcineurin B. SOS2 is a serine/threonine protein kinase in the SNF1/AMPK family. We report here that SOS3 physically interacts with and activates SOS2 protein kinase. Genetically, sos2sos3 double mutant analysis indicates that SOS2 and SOS3 function in the same pathway. Biochemically, SOS2 interacts with SOS3 in the yeast two-hybrid system and in vitro binding assays. The interaction is mediated by the C-terminal regulatory domain of SOS2. SOS3 activates SOS2 protein kinase activity in a Ca(2+)-dependent manner. Therefore, SOS3 and SOS2 define a novel regulatory pathway important for the control of intracellular ion homeostasis and salt tolerance in plants.
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PMID:The Arabidopsis SOS2 protein kinase physically interacts with and is activated by the calcium-binding protein SOS3. 1072 50

The serine/threonine protein kinase, Yak1p, functions as a negative regulator of the cell cycle in Saccharomyces cerevisiae, acting downstream of the cAMP-dependent protein kinase. In the present work we report that overexpression of haemagglutinin-tagged full-lengthYak1p and an N-terminally truncated form (residues 148-807) lead to growth arrest in PKA compromised yak1 null yeast cells. Both forms of recombinant Yak1p kinase were catalytically active and preferred myelin basic protein (MBP) as a substrate over several other proteins. Phosphopeptide analysis of bovine MBP by tandem MS revealed two major Yak1p phosphorylation sites, Thr-97 and Ser-164. Peptides containing each site were obtained and tested as Yak1p substrates. Both forms of Yak1p phosphorylated a peptide containing the Ser-164 residue with far more efficient kinetics than MBP. The maximal velocity (V(max)) values of the full-length Yak1p reaction were 110+/-21 (Ser-164) and 8.7+/-1.7 (MBP), and those of N-terminally truncated Yak1p were 560.7+/-74.8 (Ser-164) and 34. 4+/-2.2 (MBP) pmol/min per mg of protein. Although neither form of Yak1p was able to phosphorylate two generic protein tyrosine kinase substrates, both were phosphorylated on tyrosine residues in vivo and underwent tyrosine autophosphorylation when reacted with ATP in vitro. Tandem MS showed that Tyr-530 was phosphorylated both in vivo and in vitro after reaction with ATP. Pre-treatment with protein tyrosine phosphatase 1B removed all of Yak1p phosphotyrosine content and drastically reduced Yak1p activity against exogenous substrates, suggesting that the phosphotyrosine content of the enzyme is essential for its catalytic activity. Although the N-terminally truncated Yak1p was expressed at a lower level than the full-length protein, its catalytic activity and phosphotyrosine content were significantly higher than those of the full-length enzyme. Taken together, our results suggest that Yak1p is a dual specificity protein kinase which autophosphorylates on Tyr-530 and phosphorylates exogenous substrates on Ser/Thr residues.
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PMID:Saccharomyces cerevisiae Yak1p protein kinase autophosphorylates on tyrosine residues and phosphorylates myelin basic protein on a C-terminal serine residue. 1081 18

We have cloned and characterized a novel mammalian serine/threonine protein kinase WNK1 (with no lysine (K)) from a rat brain cDNA library. WNK1 has 2126 amino acids and can be detected as a protein of approximately 230 kDa in various cell lines and rat tissues. WNK1 contains a small N-terminal domain followed by the kinase domain and a long C-terminal tail. The WNK1 kinase domain has the greatest similarity to the MEKK protein kinase family. However, overexpression of WNK1 in HEK293 cells exerts no detectable effect on the activity of known, co-transfected mitogen-activated protein kinases, suggesting that it belongs to a distinct pathway. WNK1 phosphorylates the exogenous substrate myelin basic protein as well as itself mostly on serine residues, confirming that it is a serine/threonine protein kinase. The demonstration of activity was striking because WNK1, and its homologs in other organisms lack the invariant catalytic lysine in subdomain II of protein kinases that is crucial for binding to ATP. A model of WNK1 using the structure of cAMP-dependent protein kinase suggests that lysine 233 in kinase subdomain I may provide this function. Mutation of this lysine residue to methionine eliminates WNK1 activity, consistent with the conclusion that it is required for catalysis. This distinct organization of catalytic residues indicates that WNK1 belongs to a novel family of serine/threonine protein kinases.
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PMID:WNK1, a novel mammalian serine/threonine protein kinase lacking the catalytic lysine in subdomain II. 1082 64


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