Activation and Signaling by the AMP-Activated Protein Kinase in Endothelial Cells

Abstract

Abstract-The AMP-activated protein kinase (AMPK) was initially identified as the kinase that phosphorylates the 3-hydroxy 3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme for cholesterol biosynthesis. As the name suggests, the AMPK is activated by increased intracellular concentrations of AMP, and is generally described as a "metabolite-sensing kinase" and when activated initiates steps to conserve cellular energy. Although there is a strong link between the activity of the AMPK and metabolic control in muscle cells, the activity of the AMPK in endothelial cells can be regulated by stimuli that affect cellular ATP levels, such as hypoxia as well as by fluid shear stress, Ca 2ϩ -elevating agonists, and hormones such as adiponectin. To date the AMPK in endothelial cells has been implicated in the regulation of fatty acid oxidation, small G protein activity and nitric oxide production as well as inflammation and angiogenesis. Moreover, there is evidence indicating that the activation of the AMPK may help to prevent the vascular complications associated with the metabolic syndrome. Key Words: angiogenesis Ⅲ nitric oxide synthase Ⅲ atherosclerosis Ⅲ 3-hydroxy-3-methylglutaryl coenzyme A Ⅲ energy metabolism T he AMP-activated protein kinase (AMPK) is a heterotrimeric serine/threonine protein kinase consisting of the catalytic subunit (␣) and 2 regulatory subunits (␤ and ␥) that exist as multiple isoforms and splice variants, resulting in the generation of 12 possible heterotrimeric combinations. As its name suggests, the AMPK is activated in many different cell types by increased intracellular concentrations of AMP and is generally referred to as a "metabolite-sensing kinase." Indeed, the AMPK is activated following heat shock, vigorous exercise, hypoxia/ischemia, and starvation and appears to be a metabolic master switch, phosphorylating key target proteins that control flux through metabolic pathways of hepatic ketogenesis, cholesterol synthesis, lipogenesis, triglyceride synthesis, adipocyte lipolysis, skeletal muscle fatty acid oxidation, and protein synthesis (reviewed recently 1,2 ). Although the complex picture regarding the regulation of AMPK activity is far from complete, it seems safe to state that the AMPK determines whole body insulin sensitivity and may prevent insulin resistance, in part, by inhibiting pathways that antagonize insulin signaling. Through its effects on signaling, metabolism, and gene expression, the AMPK enhances insulin sensitivity and may reduce the risk of type 2 diabetes. 3 The 2 previous review articles in this series have focused on the role of the AMPK in metabolic control and insulin signaling 4 and in the heart. 5 This review focuses on the role of the AMPK in vascular cells and the data implicating defects in AMPK signaling in the development of vascular disease. Activation of the AMPKEach subunit within the heterotrimeric AMPK complex has a distinct structure and function and their interaction is necessary for the modulation of kinase activity. The ␣ subunits Ori...

Resveratrol prevents renal lipotoxicity and inhibits mesangial cell glucotoxicity in a manner dependent on the AMPK–SIRT1–PGC1α axis in db/db mice

“…Accumulated experimental evidence suggests that PPARα activation attenuates or inhibits several mediators of vascular injury, including lipotoxicty, inflammation, reactive oxygen species (ROS) generation, endothelial dysfunction, angiogenesis and thrombosis in type 2 diabetes and high-fat-diet-induced renal damage [12,13], which are all associated with AMPK activation and eNOS production [14][15][16]. PPARs activate PGC-1α/β and its key downstream effector oestrogen-related receptor (ERR)-1α, which induces mitochondrial biogenesis and enhanced mitochondrial antioxidative capacity to provide relief from oxidative stress [17,18].…”

Store-operated Ca2+ Entry (SOCE) Induced by Protease-activated Receptor-1 Mediates STIM1 Protein Phosphorylation to Inhibit SOCE in Endothelial Cells through AMP-activated Protein Kinase and p38β Mitogen-activated Protein Kinase

“…Endothelial cells express both ␣1 and ␣2 subunits (25)(26)(27)(28). The above results showed that pharmacological activation of AMPK induced STIM1 phosphorylation and suppressed SOCE, so we addressed which isoform of the ␣-subunits of AMPK were involved in regulating SOCE in HLMVECs.…”

Perilipin 5 restores the formation of lipid droplets in activated hepatic stellate cells and inhibits their activation

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