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)

Several recent studies have shown that Ca2+/calmodulin-dependent protein kinase I (CaMKI) is phosphorylated and activated by a protein kinase (CaMKK) that is itself subject to regulation by Ca2+/calmodulin. In the present study, we demonstrate that this enzyme cascade is regulated by cAMP-mediated activation of cAMP-dependent protein kinase (PKA). In vitro, CaMKK is phosphorylated by PKA and this is associated with inhibition of enzyme activity. The major site of phosphorylation is threonine 108, although additional sites are phosphorylated with lower efficiency. In vitro, CaMKK is also phosphorylated by CaMKI at the same sites as PKA, suggesting that this regulatory phosphorylation might play a role as a negative-feedback mechanism. In intact PC12 cells, activation of PKA with forskolin resulted in a rapid inhibition of both CaMKK and CaMKI activity. In hippocampal slices CaMKK was phosphorylated under basal conditions, and activation of PKA led to an increase in phosphorylation. Two-dimensional phosphopeptide mapping indicated that activation of PKA led to increased phosphorylation of multiple sites including threonine 108. These results indicate that in vitro and in intact cells the CaMKK/CaMKI cascade is subject to inhibition by PKA-mediated phosphorylation of CaMKK. The phosphorylation and inhibition of CaMKK by PKA is likely to be involved in modulating the balance between cAMP- and Ca2+-dependent signal transduction pathways.
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PMID:Inhibition of the Ca2+/calmodulin-dependent protein kinase I cascade by cAMP-dependent protein kinase. 1018 89

The Kinetworks trade mark multi-immunoblotting technique was used to evaluate the expressions of 78 protein kinases, 24 protein phosphatases and phosphorylation states of 31 phosphoproteins in thoracic spinal cord tissue from control subjects and patients having the sporadic form of amyotrophic lateral sclerosis (ALS). In both the cytosolic (C) and particulate (P) fractions of spinal cord from ALS patients as compared with controls, there were increased levels of calcium/calmodulin-dependent protein kinase kinase (CaMKK; C = 120% increase/P = 580% increase;% change, compared with control), extracellular regulated kinase 2 (ERK2; C = 120% increase/P = 170% increase), G protein-coupled receptor kinase 2 (GRK2; C = 140% increase/P = 140% increase), phospho-Y279/216 glycogen synthase kinase 3 alpha/beta (GSK3alpha/beta; C = 90% increase/P = 220% increase), protein kinase B alpha (PKBalpha; C = 360% increase/P = 200% increase), phospho-T638 PKCalpha/beta (C = 630% increase/P = 170% increase), cGMP-dependent protein kinase (PKG; C = 100% increase/P = 75% increase), phospho-T451 dsRNA-dependent protein kinase (PKR; C = 2600% increase/P = 3330% increase), ribosomal S6 kinase 1 (RSK1; C = 750% increase/P = 630% increase), phospho-T389 p70 S6 kinase (S6K; C = 1000% increase/P = 460% increase), and protein-tyrosine phosphatase 1 delta (PTP1delta; C = 43% increase/P = 70% increase). Cytosolic increases in phospho-alpha-S724/gamma-S662 adducin (C = 15650% increase), PKCalpha (C = 100% increase) and PKCzeta (C = 190% increase) were found in ALS patients as compared with controls, while particulate increases in cAMP-dependent protein kinase (PKA; 43% increase), protein kinase C beta (PKCbeta; 330% increase), and stress-activated protein kinase beta (SAPKbeta; 34% increase) were also observed. Cyclin-dependent kinase-associated phosphatase (KAP) was apparently translocated, as it was reduced (31% decrease) in cytosolic fractions but elevated (100% increase) in particulate fractions of ALS spinal cord tissue. Our observations indicate that ALS is associated with the elevated expression and/or activation of many protein kinases, including PKCalpha, PKCbeta, PKCzeta and GSK3alpha/beta, which may augment neural death in ALS, and CaMKK, PKBalpha, Rsk1, S6K, and SAPK, which may be a response to neuronal injury that potentially can mitigate cell death.
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PMID:Protein kinase and protein phosphatase expression in amyotrophic lateral sclerosis spinal cord. 1267 19

The AMP-activated protein kinase (AMPK) and cAMP signaling systems are both key regulators of cellular metabolism. In this study, we show that AMPK activity is attenuated in response to cAMP-elevating agents through modulation of at least two of its alpha subunit phosphorylation sites, viz. alpha-Thr(172) and alpha1-Ser(485)/alpha2-Ser(491), in the clonal beta-cell line INS-1 as well as in mouse embryonic fibroblasts and COS cells. Forskolin, isobutylmethylxanthine, and the glucose-dependent insulinotropic peptide inhibited AMPK activity and reduced phosphorylation of the activation loop alpha-Thr(172) via inhibition of calcium/calmodulin-dependent protein kinase kinase-alpha and -beta, but not LKB1. These agents also enhanced phosphorylation of alpha-Ser(485/491) by the cAMP-dependent protein kinase. AMPK alpha-Ser(485/491) phosphorylation was necessary but not sufficient for inhibition of AMPK activity in response to forskolin/isobutylmethylxanthine. We show that AMPK alpha-Ser(485/491) can be a site for autophosphorylation, which may play a role in limiting AMPK activation in response to energy depletion or other regulators. Thus, our findings not only demonstrate cross-talk between the cAMP/cAMP-dependent protein kinase and AMPK signaling modules, but also describe a novel mechanism by which multisite phosphorylation of AMPK contributes to regulation of its enzyme activity.
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PMID:Regulation of AMP-activated protein kinase by multisite phosphorylation in response to agents that elevate cellular cAMP. 1702 20

Geminivirus Rep-interacting kinase 1 (GRIK1) and GRIK2 constitute a small protein kinase family in Arabidopsis (Arabidopsis thaliana). An earlier study showed that a truncated version of GRIK1 binds to the geminivirus replication protein AL1. We show here both full-length GRIK1 and GRIK2 interact with AL1 in yeast two-hybrid studies. Using specific antibodies, we showed that both Arabidopsis kinases are elevated in infected leaves. Immunoblot analysis of healthy plants revealed that GRIK1 and GRIK2 are highest in young leaf and floral tissues and low or undetectable in mature tissues. Immunohistochemical staining showed that the kinases accumulate in the shoot apical meristem, leaf primordium, and emerging petiole. Unlike the protein patterns, GRIK1 and GRIK2 transcript levels only show a small increase during infection and do not change significantly during development. Treating healthy seedlings and infected leaves with the proteasome inhibitor MG132 resulted in higher GRIK1 and GRIK2 protein levels, whereas treatment with the translation inhibitor cycloheximide reduced both kinases, demonstrating that their accumulation is modulated by posttranscriptional processes. Phylogenetic comparisons indicated that GRIK1, GRIK2, and related kinases from Medicago truncatula and rice (Oryza sativa) are most similar to the yeast kinases PAK1, TOS3, and ELM1 and the mammalian kinase CaMKK, which activate the yeast kinase SNF1 and its mammalian homolog AMPK, respectively. Complementation studies using a PAK1/TOS3/ELM1 triple mutant showed that GRIK1 and GRIK2 can functionally replace the yeast kinases, suggesting that the Arabidopsis kinases mediate one or more processes during early plant development and geminivirus infection by activating SNF1-related kinases.
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PMID:Geminivirus infection up-regulates the expression of two Arabidopsis protein kinases related to yeast SNF1- and mammalian AMPK-activating kinases. 1704 Oct 27

AMPK (AMP-activated protein kinase) is activated allosterically by AMP and by phosphorylation of Thr172 within the catalytic alpha subunit. Here we show that mutations in the regulatory gamma subunit reduce allosteric activation of the kinase by AMP. In addition to its allosteric effect, AMP significantly reduces the dephosphorylation of Thr172 by PP (protein phosphatase)2Calpha. Moreover, a mutation in the gamma subunit almost completely abolishes the inhibitory effect of AMP on dephosphorylation. We were unable to detect any effect of AMP on Thr172 phosphorylation by either LKB1 or CaMKKbeta (Ca2+/calmodulin-dependent protein kinase kinase beta) using recombinant preparations of the proteins. However, using partially purified AMPK from rat liver, there was an apparent AMP-stimulation of Thr172 phosphorylation by LKB1, but this was blocked by the addition of NaF, a PP inhibitor. Western blotting of partially purified rat liver AMPK and LKB1 revealed the presence of PP2Calpha in the preparations. We suggest that previous studies reporting that AMP promotes phosphorylation of Thr172 were misinterpreted. A plausible explanation for this effect of AMP is inhibition of dephosphorylation by PP2Calpha, present in the preparations of the kinases used in the earlier studies. Taken together, our results demonstrate that AMP activates AMPK via two mechanisms: by direct allosteric activation and by protecting Thr172 from dephosphorylation. On the basis of our new findings, we propose a simple model for the regulation of AMPK in mammalian cells by LKB1 and CaMKKbeta. This model accounts for activation of AMPK by two distinct signals: a Ca2+-dependent pathway, mediated by CaMKKbeta and an AMP-dependent pathway, mediated by LKB1.
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PMID:Investigating the mechanism for AMP activation of the AMP-activated protein kinase cascade. 1714 17

AMPK is a metabolic "master" controller activated in skeletal muscle by exercise in a time and intensity dependent manner, and has been implicated in regulating metabolic pathways in muscle during physical exercise. AMPK signaling in skeletal muscle is regulated by several systemic and intracellular factors and the regulation of skeletal muscle AMPK in response to exercise is the focus of this review. Specifically, the role of LKB1 and phosphatase PP2C in nucleotide-dependent activation of AMPK, and ionized calcium in CaMKK-dependent activation of AMPK in working muscle is discussed. We also discuss the influence of reactive oxygen species produced within the muscle as well as muscle glycogen and TAK1 in regulating AMPK during exercise. Currently, during intensive contraction, activation of alpha2-AMPK seems mainly to rely on AMP accumulating from ATP-hydrolysis whereas calcium signaling may have some importance during more gentle contraction conditions. Factors that regulate alpha1-AMPK during exercise are less clear but it appears, at least to some extent, to rely on an adenine nucleotide-dependent mechanism.
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PMID:How is AMPK activity regulated in skeletal muscles during exercise? 1850 8

Oxytocin is a mammalian hormone that is released mainly after distension of the uterine cervix. In this study, we report that oxytocin stimulates intracellular release of calcium, and also activates AMPK (AMP-activated protein kinase) in C2C12 myoblast cells in a time/dose-dependent manner. Oxytocin receptor mRNA was detected in C2C12 cells. In addition, oxytocin stimulated glucose uptake and, moreover, inhibition of either CaMKK (Ca(2+)/calmodulin-dependent protein kinase kinase) or AMPK blocked oxytocin-mediated AMPK activation and glucose uptake. Taken together, our findings suggest that oxytocin may serve a peripheral metabolic function in skeletal muscle cells through the calcium-CaMKK-AMPK pathway.
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PMID:Oxytocin stimulates glucose uptake in skeletal muscle cells through the calcium-CaMKK-AMPK pathway. 1855 43

As a gatekeeper of leukocyte trafficking the vasculature fulfills an essential immune function. We have recently shown that paracellular transendothelial lymphocyte migration is controlled by intercellular adhesion molecule 1 (ICAM-1)-mediated vascular endothelial cadherin (VEC) phosphorylation [Turowski et al., J. Cell Sci. 121, 29-37 (2008)]. Here we show that endothelial nitric oxide synthase (eNOS) is a critical regulator of this pathway. ICAM-1 stimulated eNOS by a mechanism that was clearly distinct from that utilized by insulin. In particular, phosphorylation of eNOS on S1177 in response to ICAM-1 activation was regulated by src family protein kinase, rho GTPase, Ca(2+), CaMKK, and AMPK, but not Akt/PI3K. Functional neutralization of any component of this pathway or its downstream effector guanylyl cyclase significantly reduced lymphocyte diapedesis across the endothelial monolayer. In turn, activation of NO signaling promoted lymphocyte transmigration. The eNOS signaling pathway was required for T-cell transmigration across primary rat and human microvascular endothelial cells and also when shear flow was applied, suggesting that this pathway is ubiquitously used. These data reveal a novel and essential role of eNOS in basic immune function and provide a key link in the molecular network governing endothelial cell compliance to diapedesis.
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PMID:ICAM-1-mediated endothelial nitric oxide synthase activation via calcium and AMP-activated protein kinase is required for transendothelial lymphocyte migration. 1907 85

Like insulin, muscle contraction (in vitro or in situ) and exercise increase glucose uptake into skeletal muscle. However, the contraction/exercise pathway of glucose uptake in skeletal muscle is an independent pathway to that of insulin. Indeed, skeletal muscle glucose uptake is normal during exercise in those who suffer from insulin resistance and diabetes. Thus, the pathway of contraction-mediated glucose uptake into skeletal muscle provides an attractive potential target for pharmaceutical treatment and prevention of such conditions, especially as skeletal muscle is the major site of impaired glucose disposal in insulin resistance. The mechanisms regulating skeletal muscle glucose uptake during contraction have not been fully elucidated. Potential regulators include Ca(2+) (via CaMK's and/or CaMKK), AMPK, ROS, and NO signaling, with some redundancy likely to be evident within the system. In this review, we attempt to briefly synthesize current evidence regarding the potential mechanisms involved in regulating skeletal muscle glucose uptake during contraction, focusing on ROS and NO signaling. While reading this review, it will become clear that this is an evolving field of research and that much more work is required to elucidate the mechanism(s) regulating skeletal muscle glucose uptake during contraction.
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PMID:Skeletal muscle glucose uptake during exercise: a focus on reactive oxygen species and nitric oxide signaling. 1939 Nov 63

Muscle contraction stimulates glucose uptake acutely to increase energy supply, but suitable cellular models that faithfully reproduce this complex phenomenon are lacking. To this end, we have developed a cellular model of contracting C(2)C(12) myotubes overexpressing GLUT4 with an exofacial myc-epitope tag (GLUT4myc) and explored stimulation of GLUT4 traffic by physiologically relevant agents. Carbachol (an acetylcholine receptor agonist) induced a gain in cell surface GLUT4myc that was mediated by nicotinic acetylcholine receptors. Carbachol also activated AMPK, and this response was sensitive to the contractile myosin ATPase inhibitor N-benzyl-p-toluenesulfonamide. The gain in surface GLUT4myc elicited by carbachol or by the AMPK activator 5-amino-4-carboxamide-1 beta-ribose was sensitive to chemical inhibition of AMPK activity by compound C and partially reduced by siRNA-mediated knockdown of AMPK catalytic subunits or LKB1. In addition, the carbachol-induced gain in cell surface GLUT4myc was partially sensitive to chelation of intracellular calcium with BAPTA-AM. However, the carbachol-induced gain in cell surface GLUT4myc was not sensitive to the CaMKK inhibitor STO-609 despite expression of both isoforms of this enzyme and a rise in cytosolic calcium by carbachol. Therefore, separate AMPK- and calcium-dependent signals contribute to mobilizing GLUT4 in response to carbachol, providing an in vitro cell model that recapitulates the two major signals whereby acute contraction regulates glucose uptake in skeletal muscle. This system will be ideal to further analyze the underlying molecular events of contraction-regulated GLUT4 traffic.
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PMID:Contraction-related stimuli regulate GLUT4 traffic in C2C12-GLUT4myc skeletal muscle cells. 2015 55


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