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)

A mouse lymphoma tissue culture line, S49, is killed by isoproterenol, choleratoxin, or prostaglandin E1, inducers of cyclic AMP (cAMP) in these cells, or by the analog dibutyryl (db) cAMP. Cell death follows arrest in the G1 phase of the cell cycle. Mutant subclones obtained by growing S49 with dbcAMP were resistant to killing. They were deficient in cAMP-dependent protein kinase. These results are discussed in relation to the possible physiologic role of cAMP-induced cell death in T-cell differentiation.
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PMID:Mechanism of lymphoma cell death induced by cyclic AMP. 17 Aug 34

Compared to the wild-type parental line of S49 mouse lymphoma cells, intact cells of a mutant line (kin.A) are 10-fold less sensititive to biologic effects of exogenous cyclic adenosine 3':5'-monophophosphate (cAMP), such as induction of cAMP phosphodiesterase, cell cycle-specific growth inhibition, and cytolysis. The cAMP-dependent protein kinase (ATP:protein phosphotransferase; EC 2.7.1.37) activity of kin.A cells exhibits an apparent Ka for activation by cAMP 10-fold greater than that of wild type, and is much more resistant to inactivation by heat. These differences between the wild-type and mutant enzymes persist through a high degree of purification, suggesting a structural alteration in the kin.A holoenzyme. Heterologous reconstitution experiments, using separated R and C subunits of the wild-type and kin.A cAMP-dependent kinases, show that the altered cAMP affinity and thermolability are conferred by the R component of the kin.A enzyme. These results are most consistent with a structural mutation in the kin.A gene coding for the R subunit of cAMP-dependent protein kinase. Evidence for a structural mutation helps to define one mechanism of heritable variation in cultured somatic cells. The phenotype produced by the kin.A structural mutation also greatly strengthens the conslusion that cAMP-dependent protein kinase is essential for cAMP regulation of growth and enzyme induction in intact S49 cells.
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PMID:A structural gene mutation affecting the regulatory subunit of cyclic AMP-dependent protein kinase in mouse lymphoma cells. 17 91

Two-dimensional polyacrylamide gel electrophoresis is used to visualize the regulatory subunit of cAMP-dependent protein kinase from cultured S49 mouse lymphoma cells and to demonstrate its in vivo phosphorylation. Regulatory subunits from mutant cells with altered kinases exhibit at least two patterns of charge shifts consistent with substitutions of single amino acids. The direct demonstration of structural alteration of this protein provides strong evidence for structural gene mutation in this cultured cell system. While mutant and wild-type gene products co-exist in the mutant cells, there is apparently preferential expression and phosphorylation of mutant subunit in these heterozygotes.
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PMID:Mutations causing charge alterations in regulatory subunits of the cAMP-dependent protein kinase of cultured S49 lymphoma cells. 19 Nov 96

We have previously selected and characterized mutant S49 mouse lymphoma cells that possess an adenosine 3':5'-cyclic monophosphate (cAMP)-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) with an increased apparent affinity constant (Ka) for activation by cAMP. The Ka lesion in one such mutant clone has been shown to result from a structural mutation involving the kinase holoenzyme's regulatory (R) subunit. The present report examines the interaction of R and catalytic (C) subunits of the kinases in extracts of the mutant cells and the normal "wild type" (WT) parental line. Subunit recombination experiments were performed, by using purified WT and mutant R subunits, and C subunits purified from WT cells. As compared to WT R subunits, only 1/6 as much mutant R subunit was required to reassociate with and suppress 50% of C subunit activity, at equilibrium. NaSCN activates cAMP-dependent kinase of both cell types by causing the holoenzyme to dissociate. In comparison with WT, a 2-fold higher concentration of NaSCN is required to maximally activate the kinase in mutant extracts. Both the reassociation result and the increased resistance of the mutant enzyme to a nonspecific dissociating agent strongly suggest that the mutant R subunit binds C subunit more tightly than does the WT R subunit. This interpretation raises the possibility that increased R-C subunit binding affinity in the mutant cell is responsible for the increased Ka for activation by cAMP of the mutant holoenzyme, and thus for the decreased potency of cAMP in regulating intact mutant cells.
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PMID:Subunit interaction in cyclic AMP-dependent protein kinase of mutant lymphoma cells. 19 31

The ability of cyclic AMP to inhibit growth, cause cytolysis and induce synthesis of cyclic AMP-phosphodiesterase in S49.1 mouse lymphoma cells is deficient in cells selected on the basis of their resistance to killing by 2 mM dibutyryl cyclic AMP. The properties of the cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) in the cyclic AMP-sensitive (S) and cyclic AMP-resistant (R) lymphoma cells were comparatively studied. The cyclic AMP-dependent protein kinase activity or R cells cytosol exhibits an apparent Ka for activation by cyclic AMP 100-fold greater than that of the enzyme from the parental S cells. The free regulatory and catalytic subunits from both S and R kinase are thermolabile, when associated in the holoenzyme the two subunits are more stable to heat inactivation in R kinase than in S kinase. The increased heat stability of R kinase is observed however only for the enzyme in which the catalytic and cyclic AMP-binding activities are expressed at high cyclic AMP concentrations (10(-5)--10(-4) M), the activities expressed at low cyclic AMP concentrations (10(-9)--10(-6) M) being thermolabile. The regulatory subunit of S kinase can be stabilized against heat inactivation by cyclic AMP binding both at 2-10(-7) and 10(-5) M cyclic AMP concentrations. In contrast, the regulatory subunit-cyclic AMP complex from R kinase is stable to heat inactivation only when formed in the presence of high cyclic AMP concentrations (10(-5)M). The findings indicate that the transition from a cyclic AMP-sensitive to a cyclic AMP-resistant lymphoma cell phenotype is related to a structural alteration in the regulatory subunit of the cyclic AMP-dependent protein kinase which has affected the protein's affinity for cyclic AMP and its interaction with the catalytic subunit.
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PMID:Altered regulation of cyclic AMP-dependent protein kinase in a mouse lymphoma cell line. 19 71

Wild-type S49 lymphoma cells respond to cyclic adenosine 3', 5'-monophosphate (cAMP) by inducing cAMP phosphodiesterase, halting growth in the G1 phase of the cell cycle and subsequently dying. By using a counter selection procedure, we have isolated a new class of mutants of S49 cells termed "deathless" that are resistant to cytolysis, but otherwise respond like the wild-type cells to cAMP. Upon removal of the cyclic nucleotide, D-cells resume their normal growth. Unlike all other cAMP-resistant mutants of S49 cells isolated until now, the D- mutant has a functionally normal cAMP-dependent protein kinase and retains normal ability to induce phosphodiesterase and arrest cell growth in G1. It is probable that the altered gene product of the D- mutant is distal to protein kinase and in a biochemical pathway separate from that of cAMP induction of phosphodiesterase or growth arrest. The D- mutant may facilitate studies of the mechanism of cAMP-induced cytolysis and growth regulation in S49 cells.
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PMID:Cyclic AMP-induced cytolysis in S49 cells: selection of an unresponsive "deathless" mutant. 19 2

Incubation of S49 lymphoma cells with N6,O2'-dibutyryl cyclic AMP (Bt2cAMP) decreases the activities of ornithine decarboxylase (L-ornithine carboxy-lyase; EC 4.1.1.17) and S-adenosylmethionine decarboxylase (S-adenosyl-L-methionine carboxy-lyase; EC 4.1.1.50), the two principal enzymes in the pathway of polyamine synthesis. This decrease is dose-dependent, commences after a 3-hr delay, virtually abolishes the assayable activities of the two enzymes, and is not associated with a soluble inhibitor of the enzyme activities. Studies in mutant S49 clones that have altered protein kinase indicate that cAMP-dependent protein kinase mediates the decreases in enzyme activities. The dose-response pattern for the cAMP-stimulated decrease in enzyme activities parallels the pattern for the cAMP-stimulated, cell cycle-specific (G1) growth arrest of S49 cells. The activity of ornithine decarboxylase decreases faster than Bt2cAMP arrests wild-type S49 cells and, similarly, release of cells from the cAMP-stimulated arrest in G1 increases the activity of ornithine decarboxylase faster than cells exit from G1. These findings contrast with reports that cAMP induces ornithine decarboxylase in other cell types and further suggest that passage of cells through cell cycle is required for maintaining the activities of ornithine and S-adenosylmethionine decarboxylases.
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PMID:Cyclic AMP-dependent protein kinase mediates a cyclic AMP-stimulated decrease in ornithine and S-adenosylmethionine decarboxylase activities. 20 37

S49 lymphoma tissue culture cells arrest in the G1 phase of the cell cycle when treated with agents that elevate endogenous cyclic adenosine 3':5'-monophosphate (cAMP), such as cholera toxin or exogenously added active congeners of cAMP such as N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate (Bt2cAMP). This phenomenon requires that cells contain the appropriate receptors: Mutant cells deficient in adenylyl cyclase fail to arrest in response to cholera toxin, and another mutant that lacks cAMP-dependent protein kinase does not respond to cholera toxin or to Bt2cAMP. The size distribution of cell populations treated with Bt2cAMP changes in a manner that reflects only the perturbation of cell cycle distribution. Arrested G1 cells in particular have the same volume as the G1 cells of an exponentially growing population. When G1 cells that have been arrested by Bt2cAMP are grown in fresh medium free of Bt2cAMP, they begin to reenter S phase after a delay of about 6 hr and do so with pseudo-first-order kinetics, with a half-life of 5 hr. These and other properties previously described suggest that cAMP regulates S49 cell growth by physiologically significant rather than artifactual mechanisms.
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PMID:Regulation of S49 lymphoma cell growth by cyclic adenosine 3':5'-monophosphate. 21 91

Kinase-negative mutants of S49 mouse lymphoma cells are pleiotropically negative for all known cAMP-mediated responses of S49 cells and yield cell extracts which are deficient in cAMP binding activity and devoid of cAMP-dependent protein kinase activity. In hybrids between kinase-negative and wild-type cells, the mutant phenotype is dominant: the tetraploid hybrids have reduced cAMP-binding activity and undetectable cAMP-dependent kinase activity. The mutant phenotype is attributable to neither a soluble inhibitor of kinase catalytic subunit, nor a defective kinase regulatory subunit acting as an inhibitor, nor a defective catalytic subunit which sequesters regulatory subunits in inactive complexes. We propose that these mutants carry trans-dominant lesions in a regulatory locus responsible for setting intracellular levels of kinase expression.
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PMID:Kinase-negative mutants of S49 mouse lymphoma cells carry a trans-dominant mutation affecting expression of cAMP-dependent protein kinase. 21 23

A series of 2'-O-acyl derivatives of 6-thioinosine cyclic 3',5'-phosphate (6-HS-cRMP) were prepared and examined for their cytotoxic effects on S49 mouse lymphoma cells which were deficient in hypoxanthine-guanine phosphoribosyltransferase (HGPRTase). Cytotoxicity increased with the lipophilicity of the acyl group to a lowest EC50 of 65 micrometer for the 2'-O-palmityl derivative. Addition of a mutation in the gene for cAMP-dependent protein kinase to the HGPRTase-deficient cell line confers resistance to 2'-O-butyryl-cAMP but not to 2'-O-butyryl-6-HS-cRMP, indicating that the latter does not exert its toxic effect via activation of protein kinase. The time course of cell kill by 2'-O-palmityl-6-HS-cRMP resembled that of 6-mercaptopurine and not that of cyclic AMP in these cells. The data suggest that the intact cyclic nucleotides are penetrating the cells and being converted, by phosphodiesterase action and deacylation, to the first toxic metabolite of 6-mercaptopurine, thioinosinic acid.
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PMID:2'-O-Acyl-6-thioinosine cyclic 3',5'-phosphates as prodrugs of thioinosinic acid. 22 58


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