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)

We have prepared a fluorescent conjugate of porcine calmodulin with 5-(dimethylamino)-1-naphthalene-sulfonyl chloride that is highly sensitive to both calcium binding and protein binding. We have used the fluorescence of this conjugate in addition to the intrinsic peptide fluorescence to show that adrenocorticotropic hormone (ACTH), beta-endorphin, glucagon, and substance P undergo calcium-dependent binding by calmodulin, with competition for common binding sites. The dissociation constants determined in the presence of 0.85 mM CaCl2 and 0.2 N KC1, pH 7.3 at 25 degrees C, range from 1.5 muM to 3.4 muM. The alpha-melanocyte-stimulating hormone, bombesin, and somatostatin also bind, with dissociation constants between 60 muM and 90 muM. Angiotensins I and III, bradykinin, neurotensin, physalaemin, substance P octapeptide, insulin, and Leu- and Met-enkephalin show little or no binding. Sequence comparisons show that the peptides that bind calmodulin well contain regions structurally similar to the recognition sequence for the cAMP-dependent protein kinase and to the sequences surrounding phosphorylated serine residues in several calmodulin binding proteins. This result suggests that modification of calmodulin binding sites in calmodulin-dependent proteins is one of the functions of protein kinase. Calcium has a dual role in peptide binding by calmodulin. The occupation of calcium binding sites having a pK approximately 4 results in a 2-fold increase in peptide binding affinity.
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PMID:Binding of simple peptides, hormones, and neurotransmitters by calmodulin. 618 Jul 61

Prolonged incubation of quiescent 3T3, 3T6, and A431 cells with the P2Y purinoceptor agonists ATP, ADP, or AMPPNP reduced the mitogenic responses of target cells to a further challenge by these agonists, as measured by [3H]thymidine incorporation. The mitogenic desensitization was agonist-specific, for no effect was seen on DNA synthesis stimulated by epidermal growth factor, insulin, bombesin, 12-O-tetradecanoyl-phorbol-12 acetate (TPA), or adenosine. The desensitization was completely reversible, since after a 24 hr incubation in the absence of ATP, the cells responded fully to the mitogenic action of ATP. The presence of a low level of cycloheximide blocked recovery, suggesting that down-regulation of the P2Y receptor may have occurred during desensitization. In Swiss 3T3 cells, stimulation of DNA synthesis occurs predominantly by activation of arachidonic acid release, followed by its oxidation to prostaglandin E2 and stimulation of adenylyl cyclase. Interestingly, prolonged preincubation with ATP produced a similar degree of desensitization of DNA synthesis and of ATP-dependent arachidonic acid release and cAMP accumulation. Furthermore, this was true for both wild type cells and mutants with a defective cAMP-dependent protein kinase (PKA). We conclude that homologous desensitization is likely due to uncoupling of the P2Y purinoceptor from phospholipase A2, and this process does not require activation of protein kinase A.
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PMID:Homologous desensitization of ATP-stimulated mitogenesis: mechanism involves desensitization of arachidonic acid release and cAMP elevation but not the activation of protein kinase A. 759 47

To investigate the role of cAMP-dependent protein kinase (PKA) and cAMP levels in ATP-dependent mitogenesis, Swiss 3T3 cells were transfected with an expression vector coding for (i) a mutated regulatory subunit of PKA (PKA mutant) or (ii) a yeast low Km cAMP phosphodiesterase gene (PDE mutant). The PKA mutant showed 70% reduced PKA activity. Phosphodiesterase activity increased 2.5-fold in the PDE mutant, leading to a great reduction of cAMP levels stimulated by ATP and other cAMP-increasing agents. The mitogenic responses of PKA and PDE mutants to insulin, epidermal growth factor, or 12-O-tetradecanoylphorbol-13-acetate were not significantly changed. However, the further stimulation by ATP, ADP, and adenosine 5'-(beta,gamma-imido)triphosphate in the presence of these growth factors was reduced by > 80%. Mitogenic effect of prostaglandin E2, forskolin, cholera toxin, or adenosine was inhibited in both mutants. The mitogenic stimulation by dibutyryl cAMP, which is resistant to phosphodiesterase, was inhibited in the PKA mutant, but not in the PDE mutant. A partial reduction of platelet-derived growth factor- or bombesin-stimulated mitogenesis, which involves protein kinase C as well as the cAMP signal, was observed in the mutants. These genetic results confirm pharmacological data on the role of PKA and cAMP levels in mitogenesis due to ATP and other growth factors.
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PMID:Role of adenosine 3':5'-monophosphate-dependent protein kinase and cAMP levels in ATP-dependent mitogenesis in Swiss 3T3 cells. 827 49

Gastrin-releasing peptide (GRP) and bombesin apparently enhance the rate of secretion of surfactant lipids from cultured fetal rat type II pneumocytes. This effect, evident within 1h of addition of the peptide, is concentration-dependent, with a maximal response at 3.0 nM. When the effect of GRP was assessed in comparison with other known secretagogues, it was found that, whereas GRP and isoproterenol were additive in their effect, there was no response to GRP in the presence of saturating concentrations of A23187 or phorbol 12-myristate 13-acetate. This suggests that the secretory response to GRP is via activation of Ca2+/calmodulin-dependent protein kinase and/or protein kinase C and is independent of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase. This conclusion is supported by the observation that the GRP-induced secretion is inhibited by calphostin C, an inhibitor of protein kinase C, but not by H-89, an inhibitor of cAMP-dependent protein kinase. The fact that GRP regulates surfactant secretion from type II pneumocytes suggests that it and/or related peptides may play a significant role in the physiological maturation of the lung.
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PMID:Stimulation of surfactant lipid secretion from fetal type II pneumocytes by gastrin-releasing peptide. 863 24

Melanophore pigment dispersion is a sensitive bioassay for activation of the adenylyl cyclase and phospholipase C second-messenger pathways. The necessity of protein kinase activation in causing pigment dispersion was confirmed for eight agonists of endogenous melanophore receptors and for two transfected receptors. All agonists and receptors previously shown to elevate intracellular cAMP in melanophores--melanocyte stimulating hormone, light, (-) norepinephrine, 5-hydroxytrptamine, and the beta2-adrenergic receptor--were able to stimulate pigment dispersion in the presence of Ro31-8220, a potent inhibitor of protein kinase C, but were blocked in the presence of H89, an inhibitor of cAMP-dependent protein kinase. The bombesin receptor, which elevates intracellular IP3 in melanophores, was unable to stimulate pigment dispersion in the presence of Ro31-8220 or H89. Agonists whose mechanism of activation of pigment dispersion are unknown were also tested. Endothelin 3 responses were blocked by both H89 and Ro31-8220, predicting coupling to phospholipase C. Vasoactive intestinal polypeptide, oxytocin, and calcitonin gene-related peptide beta responses were blocked only by H89, predicting coupling to adenylyl cyclase.
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PMID:Melanophore pigment dispersion responses to agonists show two patterns of sensitivity to inhibitors of cAMP-dependent protein kinase and protein kinase C. 869 26

Quiescent Swiss 3T3 cells can be induced to re-enter the cell cycle by stimulation of a variety of growth factor-dependent signal transduction cascades. We have utilised this cell system to investigate the point of convergence of mitogenic signalling by analysing the changes that distinct mitogens induce in the components of the cell cycle regulatory machinery (the G1 cyclins, cdks and their inhibitors). In the presence of insulin, activation of cAMP-dependent protein kinase caused a dramatic post-transcriptional down-regulation of p27(Kip1), an increase in cyclin D3 but had little effect on cyclin D1 levels, whilst activation of protein kinase C had a more modest effect on cyclin D3 and p27(Kip1) but caused a striking elevation in the expression of cyclin D1. The neuropeptide bombesin, when combined with insulin, caused increased expression of cyclin D1 and down-regulation of p27(Kip1) mRNA and protein. Thus each combination of mitogenic agents had different effects on the components responsible for regulating the orderly progression of the cell cycle. This outcome is incompatible with a single route to mitogenesis and demonstrates that different mitogens remain distinct in the signalling responses they initiate, only converging at the levels of the expression of the D-type cyclins and the inhibitor p27(Kip1).
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PMID:Differential control of cyclins D1 and D3 and the cdk inhibitor p27Kip1 by diverse signalling pathways in Swiss 3T3 cells. 915 Mar 81

Glucose-dependent insulinotropic polypeptide (GIP) regulates glucose homeostasis and high-fat diet-induced obesity and insulin resistance. Therefore, elucidating the mechanisms that regulate GIP release is important. GIP is produced by K cells, a specific subtype of small intestinal enteroendocrine (EE) cell. Bombesin-like peptides produced by enteric neurons and luminal nutrients stimulate GIP release in vivo. We previously showed that PMA, bombesin, meat hydrolysate, glyceraldehyde, and methylpyruvate increase hormone release from a GIP-producing EE cell line (GIP/Ins cells). Here we demonstrate that bombesin and nutrients additively stimulate hormone release from GIP/Ins cells. In various cell systems, bombesin and PMA regulate cell physiology by activating PKD signaling in a PKC-dependent fashion, whereas nutrients regulate cell physiology by inhibiting AMPK signaling. Western blot analyses of GIP/Ins cells using antibodies specific for activated and/or phosphorylated forms of PKD and AMPK and one substrate for each kinase revealed that bombesin and PMA, but not nutrients, activated PKC, but not PKD. Conversely, nutrients, but not bombesin or PMA, inhibited AMPK activity. Pharmacological studies showed that PKC inhibition blocked bombesin- and PMA-stimulated hormone release, but AMPK activation failed to suppress nutrient-stimulated hormone secretion. Forced expression of constitutively active vs. dominant negative PKDs or AMPKs failed to perturb bombesin- or nutrient-stimulated hormone release. Thus, in GIP/Ins cells, PKC regulates bombesin-stimulated hormone release, whereas nutrients may control hormone release by regulating the activity of AMPK-related kinases, rather than AMPK itself. These results strongly suggest that K cells in vivo independently respond to neuronal vs. nutritional stimuli via two distinct signaling pathways.
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PMID:Bombesin and nutrients independently and additively regulate hormone release from GIP/Ins cells. 1538 72