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)

The intracellular events which are involved in controlling the G1 to S phase transition during the eucaryotic cell cycle are important to define in order to understand the mechanisms by which mitogenic and growth arrest-inducing agents control cell growth. Because a change in protein kinase activity is associated with the initial response of cells to mitogenic stimulants and growth factors, we used a kinase renaturation assay to identify specific protein kinases which are modulated as human T cells make the G1 to S phase transition after mitogenic stimulation with lectin. We identified four protein serine/threonine kinases of 180, 97, 85, and 38 kilodaltons which are increased in activity as these cells enter S phase. A-55 kDa serine/threonine kinase (PK55) was shown to have maximal activity during G0 and its activity was reduced by 95% upon movement into S phase. PK55 is inducible in human T cells by removal of interleukin 2 and low serum incubation which arrests cells in G1 phase, indicating that it is closely associated with G1 phase growth arrest. Furthermore, a similar PK55 activity was induced upon growth arrest in HL-60 cells treated with dimethyl sulfoxide and in Daudi cells treated with interferon alpha. Because the cAMP-dependent protein kinase (PK-A) family has been shown to be antiproliferative to lectin stimulated T cells, we were interested in determining whether PK55 was in fact an isozyme of PK-A. Comparative analysis using a specific peptide inhibitor of PK-A activity revealed that PK55 is catalytically distinct from PK-A. This data suggest that increases in PK55 may be associated with the growth-arrested state and further that PK55 is distinct from PK-A.
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PMID:Specific protein kinases modulated during T cell mitogenesis. Activity of a 55-kDa serine kinase is associated with growth arrest in human T cells. 153 85

Purified dihydropyridine-sensitive calcium channels from rabbit transverse-tubule membranes consist of three noncovalently associated classes of subunits: alpha (167 kDa), beta (54 kDa), and gamma (30 kDa). Cleavage of disulfide bonds reveals two distinct alpha polypeptides and an additional component, delta. The alpha 1 subunit, a 175-kDa polypeptide that is not N-glycosylated, contains the dihydropyridine binding site, cAMP-dependent protein kinase phosphorylation site(s), and substantial hydrophobic domain(s). alpha 2, a 143-kDa glycoprotein, has none of the properties characteristic of alpha 1 but binds lectins and contains about 25% N-linked carbohydrate. alpha 2 is disulfide-linked to delta, a 24- to 27-kDa glycopeptide. beta (54 kDa) contains a cAMP-dependent phosphorylation site but is not N-glycosylated and does not have a hydrophobic domain. gamma (30 kDa) has a carbohydrate content of about 30% and extensive hydrophobic domain(s). Precipitation with affinity-purified anti-alpha 1 antibodies or alpha 2-specific lentil lectin-agarose demonstrated that alpha 1 alpha 2 beta gamma delta behaves as a complex in the presence of digitonin or 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, whereas the alpha 2 delta complex dissociates from alpha 1 beta gamma in the presence of Triton X-100. A model for subunit interaction and membrane insertion is proposed on the basis of these observations.
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PMID:Subunit structure of dihydropyridine-sensitive calcium channels from skeletal muscle. 244 51

Regulatory properties of a partially purified Ca2+ -channel preparation from isolated rabbit skeletal muscle triads were examined in proteoliposomes. These properties included (i) inhibition by phenylalkylamine antagonists, such as verapamil, (ii) inhibition by the GTP-binding protein Go in the presence of guanosine 5'-[gamma-thio]triphosphate, and (iii) regulation of phenylalkylamine inhibition as a result of phosphorylation by a polypeptide-dependent protein kinase (PK-P). By selective reconstitution of protein fractions obtained by wheat germ lectin and ion-exchange chromatography, a separation of Ca2+-channel activity (fraction C) from regulatory component(s) (fraction R) responsible for verapamil sensitivity was achieved. Reconstitution of fraction C alone yielded vesicles that exhibited channel-mediated 45Ca2+ uptake that could be directly inhibited by coreconstitution of Go in the presence of guanosine 5'-[gamma-thio]triphosphate. However, the 45Ca2+ uptake obtained with fraction C was not inhibited by verapamil. Coreconstitution of fractions C and R yielded vesicles in which the sensitivity of 45Ca2+ uptake to verapamil was restored. The verapamil sensitivity of this preparation could be inhibited by PK-P. Fraction C, obtained by wheat germ agglutinin-Sepharose chromatography followed by DEAE-Sephacel chromatography, included a 180-kDa protein that was phosphorylated by cAMP-dependent protein kinase (PK-A) but not by PK-P and a 145-kDa protein (180 kDa under nonreducing conditions) that was not phosphorylated by either kinase. Fraction R contained proteins that did not adsorb to wheat germ lectin and included 165-kDa and 55-kDa proteins that were phosphorylated by PK-P but not by PK-A. These results suggest a complex model for Ca2+-channel regulation in skeletal muscle involving a number of distinct, separable protein components.
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PMID:Functional reconstitution of skeletal muscle Ca2+ channels: separation of regulatory and channel components. 245 79

We have purified putative L-type Ca2+ channels from chick heart by virtue of their associated high affinity receptors for the Ca2+ channel effectors, dihydropyridines (DHPs), and phenylalkylamines (PAAs). A peptide of 185,000-190,000 daltons was found to comigrate with the peak of DHP binding activity during purification through two successive cycles of lectin affinity chromatography and sucrose density gradient centrifugation. A previously described peptide of 140,000 daltons, whose Mr was increased to approximately 180,000 under nonreducing conditions, also copurified with the 185-kDa peptide and dihydropyridine binding activity. When cardiac membranes were photolabeled with either the dihydropyridine [3H]azidopine or the PAA [3H]azidopamil prior to purification, a single, specifically labeled component of 185,000-190,000 daltons was present in the purified fractions. The properties of this 185-kDa cardiac DHP/PAA receptor were compared to the smaller 165-kDa DHP/PAA receptor previously purified from skeletal muscle. Antibodies raised against the 165-kDa skeletal muscle DHP/PAA receptor reacted with both rabbit and chick skeletal muscle receptors, but only poorly recognized, if at all, the cardiac 185-190 kDa component. The 185-kDa peptide present in the purified fractions obtained from cardiac muscle did not undergo substantial phosphorylation by cAMP-dependent protein kinase, while the purified 165-kDa peptide from rabbit and chick skeletal muscle was a good substrate for this kinase. The results show that the DHP and PAA receptors in cardiac muscle are contained in a 185-190-kDa peptide that is significantly larger than, and structurally and immunologically different from, it skeletal muscle counterpart.
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PMID:Dihydropyridine and phenylalkylamine receptors associated with cardiac and skeletal muscle calcium channels are structurally different. 284 12

Purified testicular and ovarian luteinizing hormone/human chorionic gonadotropin (hCG) receptors are phosphorylated at serine and threonine residues by the catalytic subunit of the cAMP-dependent protein kinase (protein kinase A). Occupancy of the receptors by hCG significantly increased the rate but not the extent of phosphorylation. However, prolonged preincubation of receptors with hCG reduced the subsequent rate of receptor phosphorylation. Identical phosphopeptide maps were obtained for the phosphorylated ovarian and testicular receptors. The phosphorylated receptor, like the native receptor, bound to wheat germ lectin and hCG-Sepharose and migrated as a single band of Mr 90,000 (testis) and Mr 85,000 (ovary) on NaDodSO4/PAGE. Neuraminidase treatment of receptors caused reductions of molecular weight to 82,000 (testis) and 77,000 (ovary), and further treatment with O-Glycanase had minimal effect on molecular size. However, deglycosylation with N-Glycosidase and endoglycosidase F produced a single labeled polypeptide of Mr 59,000 for both gonadal receptors. Treatment of native receptors with neuraminidase caused no apparent change in binding of gonadotropin to blotted receptors, whereas deglycosylated receptors showed a major reduction in hormone binding. These results indicate that luteinizing hormone/hCG receptors are sialoglycoproteins with predominantly N-linked glycosyl residues that account for the size difference between testicular and ovarian receptors and that may participate in the interaction with gonadotropin. Receptor occupancy by agonist leads to a conformational change that facilitates its phosphorylation during initial binding and reduces the rate of phosphorylation after more prolonged exposure to hCG.
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PMID:Phosphorylation and glycosylation of the luteinizing hormone receptor. 292 94

The interaction of the mammalian spermatozoon with the oocyte's extracellular matrix or zona pellucida is a critical first step leading to successful fertilization. In this cell-extracellular matrix interaction it is the carbohydrate of the zona pellucida which serves as the sperm receptor and the surface of the spermatozoon which provides the lectin-like adhesion molecules. To better understand sperm-zona pellucida binding we have analyzed one specific zona binding protein (ZBP). This study has determined the mRNA sequence encoding a mammalian testis and sperm specific protein of 16,891 Da, which we have designated Sp17. Analysis of Sp17 revealed that the mRNA is present in rabbit, mouse, and human testes but not in any somatic tissue tested. In the rabbit, Sp17 is the 17-kDa member of the rabbit sperm autoantigen family of sperm specific autoantigens and is encoded by two mRNAs of 0.9 and 1.1 kb. Each mRNA has a unique 5' untranslated region but both have identical coding regions. The deduced amino acid sequence of the Sp17 ZBP showed several interesting features, including a similarity to the N-terminal of human testis cAMP-dependent protein kinase. Localization of Sp17 on live spermatozoa using antibodies to recombinant Sp17 or to the Sp17 peptide, G22C, revealed that the peptide backbone of Sp17 is inaccessible until the acrosome reaction begins. However, on paraformaldehyde fixed, acrosome intact spermatozoa, the peptide backbone is accessible to the antibodies which localize Sp17 to the apical surface. In the rabbit as well as other similar species in which the corona radiata (granulosa) cells adhere tightly to the zona pellucida and synthesize zona glycoproteins, the fertilizing spermatozoon may have already begun the acrosome reaction within the cumulus oophorus. Thus, the rabbit sperm surface would be modified to expose the Sp17 polypeptide during the final phase of cumulus passage and consequently Sp17 would be available for initial zona binding. The present study has also demonstrated that recombinant Sp17 can bind zona pellucida, dextran, and dextran sulfate.
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PMID:Sequence of a rabbit sperm zona pellucida binding protein and localization during the acrosome reaction. 752 87

Post-confluent populations of LLC-PK1 cells express many glycoproteins at the surface, including glycoproteins which bind the lectin Dolichos biflorus agglutinin (DBA). DBA-binding glycoproteins are localized preferentially to the apical cell surface and exhibit molecular weights ranging from less than 30 kDa to greater than 200 kDa. Subconfluent cell populations exhibit little surface DBA binding. Upon attaining confluence DBA binding capacity increases progressively over several days. This correlates roughly with increasing activities of several differentiated apical membrane functions. Expression of DBA binding sites at the surface occurs on a cell-by-cell basis. An increasing level of surface DBA binding in the cell population corresponds to an increasing proportion of the cell population expressing binding sites. Activation of cAMP-dependent protein kinase in post-confluent cell populations, and to a lesser extent in subconfluent populations, increases surface DBA binding sites by a protein synthesis-dependent mechanism after a lag period of at least 24 h. This results from increases in both the proportion of cells expressing surface binding sites and the level of binding sites on individual cells.
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PMID:Cell surface expression of DBA binding sites in LLC-PK1 cells increases at confluence and is enhanced by PKA activation. 768 71

Previous studies demonstrated that, upon attaining confluence, a clone of the renal epithelial cell, LLC-PK1, expressed progressively binding sites for the lectin Dolichos biflorus agglutinin (DBA) at the apical cell surface. Activation of cAMP-dependent protein kinase enhanced surface expression dramatically. The goal of this study was to define the process leading to surface expression of DBA binding sites and to investigate further the role of cAMP-dependent protein kinase in modulating surface expression. Both subconfluent and confluent cells exhibited intracellular DBA binding sites (50-70% of total cellular binding sites) in a perinuclear vesicular compartment which was disrupted by Brefeldin A treatment. Both total cellular content and the proportion of DBA binding sites at the cell surface increased modestly after confluence was attained. A 48 h treatment of cells with 1-methyl-3-isobutyl xanthine, a phosphodiesterase inhibitor, dramatically increased the level of cellular DBA binding sites as well as the proportion of DBA binding sites at the cell surface. Analysis of two mutants of this cell line suggests that the effect of 1-methyl-3-isobutyl xanthine requires cAMP-dependent protein kinase activity but is not due to cAMP-dependent protein kinase-mediated activation of gene transcription.
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PMID:cAMP-dependent protein kinase modulates expression and subcellular localization of Dolichos biflorus agglutinin binding sites in renal epithelial cells. 769 30

In Alzheimer's disease (AD) brain, microtubule-associated protein tau is abnormally modified by hyperphosphorylation and glycosylation, and is aggregated as neurofibrillary tangles of paired helical filaments. To investigate the role of tau glycosylation in neurofibrillary pathology, we isolated various pools of tau protein from AD brain which represent different stages of tau pathology. We found that the non-hyperphosphorylated tau from AD brain but not normal brain tau was glycosylated. Monosaccharide composition analyses and specific lectin blots suggested that the tau in AD brain was glycosylated mainly through N-linkage. In vitro phosphorylation indicated that the glycosylated tau was a better substrate for cAMP-dependent protein kinase than the deglycosylated tau. These results suggest that the glycosylation of tau is an early abnormality that can facilitate the subsequent abnormal hyperphosphorylation of tau in AD brain.
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PMID:Role of glycosylation in hyperphosphorylation of tau in Alzheimer's disease. 1185 60

HIP/PAP is a C-type lectin overexpressed in hepatocellular carcinoma (HCC). Pleiotropic biological activities have been ascribed to this protein, but little is known about the function of HIP/PAP in the liver. In this study, therefore, we searched for proteins interacting with HIP/PAP by screening a HCC cDNA expression library. We have identified the RII alpha regulatory subunit of cAMP-dependent protein kinase (PKA) as a partner of HIP/PAP. HIP/PAP and RII alpha were coimmunoprecipitated in HIP/PAP expressing cells. The biological relevance of the interaction between these proteins was established by demonstrating, using fractionation methods, that they are located in a same subcellular compartment. Indeed, though HIP/PAP is a protein secreted via the Golgi apparatus we showed that a fraction of HIP/PAP escaped the secretory apparatus and was recovered in the cytosol. Basal PKA activity was increased in HIP/PAP expressing cells, suggesting that HIP/PAP may alter PKA signalling. Indeed, we showed, using a thymidine kinase-luciferase reporter plasmid in which a cAMP responsive element was inserted upstream of the thymidine kinase promoter, that luciferase activity was enhanced in HIP/PAP expressing cells. Thus our findings suggest a novel mechanism for the biological activity of the HIP/PAP lectin.
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PMID:HIP/PAP, a C-type lectin overexpressed in hepatocellular carcinoma, binds the RII alpha regulatory subunit of cAMP-dependent protein kinase and alters the cAMP-dependent protein kinase signalling. 1537 27


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