The Stimulation of Glycolysis by Hypoxia in Activated Monocytes Is Mediated by AMP-activated Protein Kinase and Inducible 6-Phosphofructo-2-kinase

Abstract

The activation of monocytes involves a stimulation of glycolysis, release of potent inflammatory mediators, and alterations in gene expression. All of these processes are known to be further increased under hypoxic conditions. The activated monocytes express inducible 6-phosphofructo-2-kinase (iPFK-2), which synthesizes fructose 2,6-bisphosphate, a stimulator of glycolysis. During ischemia, AMP-activated protein kinase (AMPK) activates the homologous heart 6-phosphofructo-2-kinase isoform by phosphorylating its Ser-466. Here, we studied the involvement of AMPK and iPFK-2 in the stimulation of glycolysis in activated monocytes under hypoxia. iPFK-2 was phosphorylated on the homologous serine (Ser-461) and activated by AMPK in vitro. The activation of human monocytes by lipopolysaccharide induced iPFK-2 expression and increased fructose 2,6-bisphosphate content and glycolysis. The incubation of activated monocytes with oligomycin, an inhibitor of oxidative phosphorylation, or under hypoxic conditions activated AMPK and further increased iPFK-2 activity, fructose 2,6-bisphosphate content, and glycolysis. In cultured human embryonic kidney 293 cells, the expression of a dominant-negative AMPK prevented both the activation and phosphorylation of co-transfected iPFK-2 by oligomycin. It is concluded that the stimulation of glycolysis by hypoxia in activated monocytes requires the phosphorylation and activation of iPFK-2 by AMPK.

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

“…Co Control, Tro troglitazone product inhibition by glucose-6-phosphate. AMPK accelerates glycolytic flux by directly phosphorylating and activating phosphofructokinase 2 in cardiomyocytes, monocytes and astrocytes [62][63][64]. The ensuing increase in fructose-2,6-bisphosphate and the resulting allosteric stimulation of phosphofructokinase 1 increases the utilisation of glucose-6-phosphate, thus relieving an inhibitory allosteric input on hexokinase.…”

Targeting cancer metabolism: a therapeutic window opens

“…PFK2FB3 has almost no phosphatase activity, and kinase activity is influenced by several factors implicated in controlling cancer metabolism including metabolite levels as well as RAS, MYC, and AMPK signaling 105,108,109 . Small molecule inhibitors of PFK2FB3 have been NAMPT inhibition in cells has an effect primarily on the cytosolic (rather than the mitochondrial) NAD + pool 121 .…”

Stimulators of AMP‐activated protein kinase inhibit the respiratory burst in human neutrophils

“…AMPK also modulates positively other ATPgenerating pathways, such as glycolysis [16] and fatty acid oxidation [17]. It has been shown that an adenosine analog, 5-aminoimidazole-4-carboxamide 1-b-D D -ribofuranoside (AI-CAR), which enters cells and is phosphorylated by adenosine kinase to form AICAR-5 0 -monophosphate, is itself a potent stimulator of AMPK [16,18], and also an intermediate in the purine de novo synthesis pathway.…”

“…Intracellular 5 0 -AMP activates AMPK via several distinct mechanisms: (i) 5 0 -AMP causes a direct allosteric activation of AMPK [13]; (ii) binding of 5 0 -AMP to AMPK renders it a better substrate for the upstream AMPK kinase (AMPKK/LKB1), or a worse substrate for protein phosphatases [13][14][15]; and (iii), the upstream kinase AMPKK/LKBl, which is also allosterically stimulated by 5 0 -AMP, in turn phosphorylates and activates AMPK [14,15]. AMPK also modulates positively other ATPgenerating pathways, such as glycolysis [16] and fatty acid oxidation [17]. It has been shown that an adenosine analog, 5-aminoimidazole-4-carboxamide 1-b-D D -ribofuranoside (AI-CAR), which enters cells and is phosphorylated by adenosine kinase to form AICAR-5 0 -monophosphate, is itself a potent stimulator of AMPK [16,18], and also an intermediate in the purine de novo synthesis pathway.…”