AMP-activated protein kinase activates transcription of the UCP3 and HKII genes in rat skeletal muscle

Abstract

. AMP-activated protein kinase activates transcription of the UCP3 and HKII genes in rat skeletal muscle. Am J Physiol Endocrinol Metab 283: E1239-E1248, 2002. First published September 11, 2002 10.1152/ajpendo. 00278.2002.-AMP-activated protein kinase (AMPK) has recently emerged as a key signaling protein in skeletal muscle, coordinating the activation of both glucose and fatty acid metabolism in response to increased cellular energy demand. To determine whether AMPK signaling may also regulate gene transcription in muscle, rats were given a single subcutaneous injection (1 mg/g) of the AMP analog 5-aminoimidazole-4-carboxamide-1-␤-D-ribonucleoside (AICAR). AICAR injection activated (P Ͻ 0.05) AMPK-␣2 (ϳ2.5-fold) and transcription of the uncoupling protein-3 (UCP3, ϳ4-fold) and hexokinase II (HKII, ϳ10-fold) genes in both red and white skeletal muscle. However, AICAR injection also elicited (P Ͻ 0.05) an acute drop (60%) in blood glucose and a sustained (2-h) increase in blood lactate, prompting concern regarding the specificity of AICAR on transcription. To maximize AMPK activation in muscle while minimizing potential systemic counterregulatory responses, a single-leg arterial infusion technique was employed in fully conscious rats. Relative to saline-infused controls, single-leg arterial infusion of AICAR (0.125, 0.5, and 2.5 g ⅐ g Ϫ1 ⅐ min Ϫ1 for 60 min) induced a dose-dependent increase (2-to 4-fold, P Ͻ 0.05) in UCP3 and HKII transcription in both red and white skeletal muscle. Importantly, AICAR infusion activated transcription only in muscle from the infused leg and had no effect on blood glucose or lactate levels. These data provide evidence that AMPK signaling is linked to the transcriptional regulation of select metabolic genes in skeletal muscle.5-aminoimidazole-4-carboxamide ribonucleoside; single-leg arterial infusion; rat; AMP kinase phosphorylation AMP-ACTIVATED PROTEIN KINASE (AMPK) is a highly conserved metabolite-sensing protein kinase found in all eukaryotic cells (12). In mammals, the AMPK enzyme is composed of a catalytic ␣-subunit and two regulatory subunits, ␤ and ␥, each of which is encoded for by either two (␣ 1 , ␣ 2 , ␤ 1 , ␤ 2 ) (40, 42) or three (␥ 1 , ␥ 2 , ␥ 3 ) (6) genes. Although not completely defined, it is thought that AMP activates AMPK by binding to the interface between the ␣-and ␥-subunits, disrupting an autoinhibitory domain within the ␣-subunit (13). AMPK is also stimulated by phosphorylation of a regulatory site (Thr 172 ) in the catalytic domain of the ␣-subunit, a reaction catalyzed by an upstream kinase, AMPK kinase (AMPKK), which is also activated by AMP (14,15,41). Thus full activation of AMPK is achieved by a combination of AMP-mediated allosteric activation of AMPK and its upstream kinase AMPKK, and by covalent phosphorylation of the AMPK ␣-subunit by AMPKK. Although the resting concentration of AMP is typically 100-fold lower than ATP (a competitive inhibitor of AMPK), AMP concentration increases dramatically under conditions of accelerated ATP utilization,...

Role of AMP-activated protein kinase in the coordinated expression of genes controlling glucose and lipid metabolism in mouse white skeletal muscle

“…In line with this, GYS levels in Tg-Prkag3 225Q mice were lower under fasting conditions. Our finding of a reciprocal relationship between the transcription of genes regulating glucose and lipid/oxidative metabolism is in contrast with previous findings of a concerted increase in the expression of genes along these metabolic pathways in AICAR-treated rodents [10,42,43]. The interpretation of previous studies that adopted chronic AICAR treatment as a means of chemically activating AMPK has been hindered by the non-specificity of the compound, which also activates other AMP-regulated enzymes [7,44].…”

Troglitazone causes acute mitochondrial membrane depolarisation and an AMPK-mediated increase in glucose phosphorylation in muscle cells

“…AMPK activation can induce gene expression of hexokinase II, an isoform expressed in muscle [61]. However, given the short duration of troglitazone stimulation in the present study (30 min) it is unlikely that sufficient hexokinase II biosynthesis occurs in that time to mediate the stimulation of 2-DGP accumulation.…”

Expression of Uncoupling Protein 3 and GLUT4 Gene in Skeletal Muscle of Preterm Newborns: Possible Control by AMP-Activated Protein Kinase

“…Activation of AMPK in skeletal muscle in response to contraction results in increased glucose uptake (22) and FA oxidation (23). Moreover, activation of AMPK in skeletal muscle by an adenosine analog (5-aminoimidazole-4-carboxamide-1-␤-D-ribofuranoside) increases expression of genes for GLUT4, and for mitochondrial proteins (24), including UCP3 (25)(26)(27)(28)(29). AMPK has also a role in the regulation of the transcription of genes involved in glucose and lipid metabolism in muscle during starvation (30).…”