Physiological role of AMP-activated protein kinase in the heart: graded  activation during exercise

AMP-activated protein kinase (AMPK) is emerging as a key signaling pathway that modulates cellular metabolic processes. In skeletal muscle, AMPK is activated during exercise. Increased myocardial substrate metabolism during exercise could be explained by AMPK activation. Although AMPK is known to be activated during myocardial ischemia, it remains uncertain whether AMPK is activated in response to the physiological increases in cardiac work associated with exercise. Therefore, we evaluated cardiac AMPK activity in rats at rest and after 10 min of treadmill running at moderate (15% grade, 16 m/min) or high (15% grade, 32 m/min) intensity. Total AMPK activity in the heart increased in proportion to exercise intensity ( P < 0.05). AMPK activity associated with the α2-catalytic subunit increased 2.8 ± 0.4-fold ( P < 0.02 vs. rest) and 4.5 ± 0.6-fold ( P < 0.001 vs. rest) with moderate- and high-intensity exercise, respectively. AMPK activity associated with the α1-subunit increased to a lesser extent. Phosphorylation of the Thr172-regulatory site on AMPK α-catalytic subunits increased during exercise ( P < 0.001). There was no increase in Akt phosphorylation during exercise. The changes in AMPK activity during exercise were associated with physiological AMPK effects (GLUT4 translocation to the sarcolemma and ACC phosphorylation). Thus cardiac AMPK activity increases progressively with exercise intensity, supporting the hypothesis that AMPK has a physiological role in the heart.

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Characterization of the Role of AMP-Activated Protein Kinase in the Regulation of Glucose-Activated Gene Expression Using Constitutively Active and Dominant Negative Forms of the Kinase

Molecular and Cellular Biology ◽

10.1128/mcb.20.18.6704-6711.2000 ◽

2000 ◽

Vol 20 (18) ◽

pp. 6704-6711 ◽

Cited By ~ 293

Author(s):

Angela Woods ◽

Dalila Azzout-Marniche ◽

Marc Foretz ◽

Silvie C. Stein ◽

Patricia Lemarchand ◽

...

Keyword(s):

Gene Expression ◽

Protein Kinase ◽

Fatty Acid Synthase ◽

Physiological Role ◽

Rat Hepatocytes ◽

Dominant Negative ◽

Ampk Activity ◽

Amp Activated Protein Kinase ◽

Constitutively Active

ABSTRACT In the liver, glucose induces the expression of a number of genes involved in glucose and lipid metabolism, e.g., those encoding L-type pyruvate kinase and fatty acid synthase. Recent evidence has indicated a role for the AMP-activated protein kinase (AMPK) in the inhibition of glucose-activated gene expression in hepatocytes. It remains unclear, however, whether AMPK is involved in the glucose induction of these genes. In order to study further the role of AMPK in regulating gene expression, we have generated two mutant forms of AMPK. One of these (α1312) acts as a constitutively active kinase, while the other (α1DN) acts as a dominant negative inhibitor of endogenous AMPK. We have used adenovirus-mediated gene transfer to express these mutants in primary rat hepatocytes in culture in order to determine their effect on AMPK activity and the transcription of glucose-activated genes. Expression of α1312 increased AMPK activity in hepatocytes and blocked completely the induction of a number of glucose-activated genes in response to 25 mM glucose. This effect is similar to that observed following activation of AMPK by 5-amino-imidazolecarboxamide riboside. Expression of α1DN markedly inhibited both basal and stimulated activity of endogenous AMPK but had no effect on the transcription of glucose-activated genes. Our results suggest that AMPK is involved in the inhibition of glucose-activated gene expression but not in the induction pathway. This study demonstrates that the two mutants we have described will provide valuable tools for studying the wider physiological role of AMPK.

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AMP kinase is not required for the GLUT4 response to exercise and denervation in skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00080.2004 ◽

2004 ◽

Vol 287 (4) ◽

pp. E739-E743 ◽

Cited By ~ 46

Author(s):

Burton F. Holmes ◽

David B. Lang ◽

Morris J. Birnbaum ◽

James Mu ◽

G. Lynis Dohm

Keyword(s):

Skeletal Muscle ◽

Dominant Negative ◽

Treadmill Running ◽

Wild Type ◽

Α Subunit ◽

Ampk Activity ◽

Denervated Muscles ◽

Amp Activated Protein Kinase ◽

Response To Exercise

An acute bout of exercise increases muscle GLUT4 mRNA in mice, and denervation decreases GLUT4 mRNA. AMP-activated protein kinase (AMPK) activity in skeletal muscle is also increased by exercise, and GLUT4 mRNA is increased in mouse skeletal muscle after treatment with AMPK activator 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside(AICAR). These findings suggest that AMPK activation might be responsible for the increase in GLUT4 mRNA expression in response to exercise. To investigate the role of AMPK in GLUT4 regulation in response to exercise and denervation, transgenic mice with a mutated AMPK α-subunit (dominant negative; AMPK-DN) were studied. GLUT4 did not increase in AMPK-DN mice that were treated with AICAR, demonstrating that muscle AMPK is inactive. Exercise (two 3-h bouts of treadmill running separated by 1 h of rest) increased GLUT4 mRNA in both wild-type and AMPK-DN mice. Likewise, denervation decreased GLUT4 mRNA in both wild-type and AMPK-DN mice. GLUT4 mRNA was also increased by AICAR treatment in both the innervated and denervated muscles. These data demonstrate that AMPK is not required for the response of GLUT4 mRNA to exercise and denervation.

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Physiological modulation of CFTR activity by AMP-activated protein kinase in polarized T84 cells

AJP Cell Physiology ◽

10.1152/ajpcell.00227.2002 ◽

2003 ◽

Vol 284 (5) ◽

pp. C1297-C1308 ◽

Cited By ~ 84

Author(s):

Kenneth R. Hallows ◽

Gary P. Kobinger ◽

James M. Wilson ◽

Lee A. Witters ◽

J. Kevin Foskett

Keyword(s):

Protein Kinase ◽

Short Circuit ◽

Basolateral Membrane ◽

Physiological Role ◽

Dominant Negative ◽

T84 Cells ◽

Physiological Relevance ◽

Polarized Epithelia ◽

Ampk Activity ◽

Amp Activated Protein Kinase

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated, ATP-gated Cl− channel and cellular conductance regulator, but the detailed mechanisms of CFTR regulation and its regulation of other transport proteins remain obscure. We previously identified the metabolic sensor AMP-activated protein kinase (AMPK) as a novel protein interacting with CFTR and found that AMPK phosphorylated CFTR and inhibited CFTR-dependent whole cell conductances when coexpressed with CFTR in Xenopus oocytes. To address the physiological relevance of the CFTR-AMPK interaction, we have now studied polarized epithelia and have evaluated the localization of endogenous AMPK and CFTR and measured CFTR activity with modulation of AMPK activity. By immunofluorescent imaging, AMPK and CFTR share an overlapping apical distribution in several rat epithelial tissues, including nasopharynx, submandibular gland, pancreas, and ileum. CFTR-dependent short-circuit currents ( Isc ) were measured in polarized T84 cells grown on permeable supports, and several independent methods were used to modulate endogenous AMPK activity. Activation of endogenous AMPK with the cell-permeant adenosine analog 5-amino-4-imidazolecarboxamide-1-β-d-ribofuranoside (AICAR) inhibited forskolin-stimulated CFTR-dependent I sc in nonpermeabilized monolayers and monolayers with nystatin permeabilization of the basolateral membrane. Raising intracellular AMP concentration in monolayers with basolateral membranes permeabilized with α-toxin also inhibited CFTR, an effect that was unrelated to adenosine receptors. Finally, overexpression of a kinase-dead mutant AMPK-α1 subunit (α1-K45R) enhanced forskolin-stimulated I sc in polarized T84 monolayers, consistent with a dominant-negative reduction in the inhibition of CFTR by endogenous AMPK. These results indicate that AMPK plays a physiological role in modulating CFTR activity in polarized epithelia and suggest a novel paradigm for the coupling of ion transport to cellular metabolism.

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Role of Hypothalamic Adenosine 5′-Monophosphate-Activated Protein Kinase in the Impaired Counterregulatory Response Induced by Repetitive Neuroglucopenia

Endocrinology ◽

10.1210/en.2006-1039 ◽

2007 ◽

Vol 148 (3) ◽

pp. 1367-1375 ◽

Cited By ~ 59

Author(s):

Thierry Alquier ◽

Junji Kawashima ◽

Youki Tsuji ◽

Barbara B. Kahn

Keyword(s):

Protein Kinase ◽

Glycogen Content ◽

Glucose Sensor ◽

Critical Role ◽

Glucose Sensing ◽

Dorsomedial Hypothalamus ◽

Hormone Responses ◽

Ampk Activity ◽

Amp Activated Protein Kinase

Antecedent hypoglycemia blunts counterregulatory responses that normally restore glycemia, a phenomenon known as hypoglycemia-associated autonomic failure (HAAF). The mechanisms leading to impaired counterregulatory responses are largely unknown. Hypothalamic AMP-activated protein kinase (AMPK) acts as a glucose sensor. To determine whether failure to activate AMPK could be involved in the etiology of HAAF, we developed a model of HAAF using repetitive intracerebroventricular (icv) injection of 2-deoxy-d-glucose (2DG) resulting in transient neuroglucopenia in normal rats. Ten minutes after a single icv injection of 2DG, both α1- and α2-AMPK activities were increased 30–50% in arcuate and ventromedial/dorsomedial hypothalamus but not in other hypothalamic regions, hindbrain, or cortex. Increased AMPK activity persisted in arcuate hypothalamus at 60 min after 2DG injection when serum glucagon and corticosterone levels were increased 2.5- to 3.4-fold. When 2DG was injected icv daily for 4 d, hypothalamic α1- and α2-AMPK responses were markedly blunted in arcuate hypothalamus, and α1-AMPK was also blunted in mediobasal hypothalamus 10 min after 2DG on d 4. Both AMPK isoforms were activated normally in arcuate hypothalamus at 60 min. Counterregulatory hormone responses were impaired by recurrent neuroglucopenia and were partially restored by icv injection of 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside, an AMPK activator, before 2DG. Glycogen content increased 2-fold in hypothalamus after recurrent neuroglucopenia, suggesting that glycogen supercompensation could be involved in down-regulating the AMPK glucose-sensing pathway in HAAF. Thus, activation of hypothalamic AMPK may be important for the full counterregulatory hormone response to neuroglucopenia. Furthermore, impaired or delayed AMPK activation in specific hypothalamic regions may play a critical role in the etiology of HAAF.

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Regulation of glucose transport by the AMP-activated protein kinase

Proceedings of The Nutrition Society ◽

10.1079/pns2004340 ◽

2004 ◽

Vol 63 (2) ◽

pp. 205-210 ◽

Cited By ~ 24

Author(s):

Nobuharu Fujii ◽

William G. Aschenbach ◽

Nicolas Musi ◽

Michael F. Hirshman ◽

Laurie J. Goodyear

Keyword(s):

Protein Kinase ◽

Glucose Transport ◽

Glycogen Content ◽

Acid Oxidation ◽

Ampk Activation ◽

Muscle Biology ◽

Ampk Activity ◽

Energy Sensing ◽

Amp Activated Protein Kinase

The AMP-activated protein kinase (AMPK) is an energy-sensing enzyme that is activated during exercise and muscle contraction as a result of acute decreases in ATP:AMP and phosphocreatine:creatine. Physical exercise increases muscle glucose uptake, enhances insulin sensitivity and leads to fatty acid oxidation in muscle. An important issue in muscle biology is to understand whether AMPK plays a role in mediating these metabolic processes. AMPK has also been implicated in regulating gene transcription and, therefore, may function in some of the cellular adaptations to training exercise. Recent studies have shown that the magnitude of AMPK activation and associated metabolic responses are affected by factors such as glycogen content, exercise training and fibre type. There have also been conflicting reports as to whether AMPK activity is necessary for contraction-stimulated glucose transport. Thus, during the next several years considerably more research will be necessary in order to fully understand the role of AMPK in regulating glucose transport in skeletal muscle.

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AMP-Activated Protein Kinase and Host Defense against Infection

International Journal of Molecular Sciences ◽

10.3390/ijms19113495 ◽

2018 ◽

Vol 19 (11) ◽

pp. 3495 ◽

Cited By ~ 12

Author(s):

Prashanta Silwal ◽

Jin Kim ◽

Jae-Min Yuk ◽

Eun-Kyeong Jo

Keyword(s):

Protein Kinase ◽

Ebola Virus ◽

Viral Infections ◽

Parasitic Infections ◽

Host Defenses ◽

Adaptive Immune ◽

Pathological Conditions ◽

Ampk Activity ◽

Amp Activated Protein Kinase

5′-AMP-activated protein kinase (AMPK) plays diverse roles in various physiological and pathological conditions. AMPK is involved in energy metabolism, which is perturbed by infectious stimuli. Indeed, various pathogens modulate AMPK activity, which affects host defenses against infection. In some viral infections, including hepatitis B and C viral infections, AMPK activation is beneficial, but in others such as dengue virus, Ebola virus, and human cytomegaloviral infections, AMPK plays a detrimental role. AMPK-targeting agents or small molecules enhance the antiviral response and contribute to the control of microbial and parasitic infections. In addition, this review focuses on the double-edged role of AMPK in innate and adaptive immune responses to infection. Understanding how AMPK regulates host defenses will enable development of more effective host-directed therapeutic strategies against infectious diseases.

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The regulation of AMP-activated protein kinase by phosphorylation

Biochemical Journal ◽

10.1042/bj3450437 ◽

2000 ◽

Vol 345 (3) ◽

pp. 437-443 ◽

Cited By ~ 270

Author(s):

Silvie C. STEIN ◽

Angela WOODS ◽

Neil A. JONES ◽

Matthew D. DAVISON ◽

David CARLING

Keyword(s):

Protein Kinase ◽

Site Directed Mutagenesis ◽

Wild Type ◽

Aspartic Acid Residue ◽

Α Subunit ◽

Ampk Activity ◽

Amp Activated Protein Kinase ◽

Mutant Complex

The AMP-activated protein kinase (AMPK) cascade is activated by an increase in the AMP/ATP ratio within the cell. AMPK is regulated allosterically by AMP and by reversible phosphorylation. Threonine-172 within the catalytic subunit (α) of AMPK (Thr172) was identified as the major site phosphorylated by the AMP-activated protein kinase kinase (AMPKK) in vitro. We have used site-directed mutagenesis to study the role of phosphorylation of Thr172 on AMPK activity. Mutation of Thr172 to an aspartic acid residue (T172D) in either α1 or α2 resulted in a kinase complex with approx. 50% the activity of the corresponding wild-type complex. The activity of wild-type AMPK decreased by greater than 90% following treatment with protein phosphatases, whereas the activity of the T172D mutant complex fell by only 10-15%. Mutation of Thr172 to an alanine residue (T172A) almost completely abolished kinase activity. These results indicate that phosphorylation of Thr172 accounts for most of the activation by AMPKK, but that other sites are involved. In support of this we have shown that AMPKK phosphorylates at least two other sites on the α subunit and one site on the β subunit. Furthermore, we provide evidence that phosphorylation of Thr172 may be involved in the sensitivity of the AMPK complex to AMP.

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Physiological role of AMP-activated protein kinase (AMPK): insights from knockout mouse models

Biochemical Society Transactions ◽

10.1042/bst0310216 ◽

2003 ◽

Vol 31 (1) ◽

pp. 216-219 ◽

Cited By ~ 161

Author(s):

B. Viollet ◽

F. Andreelli ◽

S.B. Jørgensen ◽

C. Perrin ◽

D. Flamez ◽

...

Keyword(s):

Skeletal Muscle ◽

Insulin Secretion ◽

Protein Kinase ◽

Mouse Models ◽

Knockout Mouse ◽

Glycogen Synthesis ◽

Physiological Role ◽

Amp Activated Protein Kinase

AMP-activated protein kinase (AMPK) is viewed as a fuel sensor for glucose and lipid metabolism. To understand better the physiological role of the catalytic AMPK subunit isoforms, we generated two knockout mouse models with the α1 (AMPKα1−/−) and α2 (AMPKα2−/−) catalytic subunit genes deleted. No defect in glucose homoeostasis was observed in AMPKα1−/− mice. On the other hand, AMPKα2−/− mice presented high plasma glucose levels and low plasma insulin concentrations in the fed period and during the glucose tolerance test. Nevertheless, in isolated AMPKα2−/− pancreatic islets, glucose-stimulated insulin secretion was not affected. Surprisingly, AMPKα2−/− mice were insulin-resistant and had reduced muscle glycogen synthesis as assessed in vivo by the hyperinsulinaemic euglycaemic clamp procedure. Reduction of insulin sensitivity and glycogen synthesis were not dependent on the lack of AMPK in skeletal muscle, since mice expressing a dominant inhibitory mutant of AMPK in skeletal muscle were not affected and since insulin-stimulated glucose transport in incubated muscles in vitro was normal in AMPKα2−/− muscles. Furthermore, AMPKα2−/− mice have a higher sympathetic tone, as shown by increased catecholamine urinary excretion. Increased adrenergic tone could explain both decreased insulin secretion and insulin resistance observed in vivo in AMPKα2−/− mice. We suggest that the α2 catalytic subunit of AMPK plays a major role as a fuel sensor by modulating the activity of the autonomous nervous system in vivo.

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