Regulation of energy metabolism in macrophages during hypoxia. Roles of fructose 2,6-bisphosphate and ribose 1,5-bisphosphate.
Macrophages can adapt to the absence of oxygen by switching to anaerobic glycolysis. In this study, we investigated (a) the roles of fructose 2,6-bisphosphate (Fru-2,6-P2) and ribose 1,5-bisphosphate (Rib-1,5-P2), potent activators of phosphofructokinase, (b) the enzymes responsible for the synthesis of Rib-1,5-P2, and (c) the mechanisms of regulation of these enzymes in H36.12j macrophages during the initial phase of hypoxia. Within 1 min after initiating hypoxia, glycolysis was activated through activation of phosphofructokinase. Over the same period, Fru-2,6-P2 decreased 50% and recovered completely upon reoxygenation. Similar changes in cAMP levels were observed. In contrast, the Rib-1,5-P2 concentration rapidly increased to a maximum level of 8.0 +/- 0.9 nmol/g cell 30 s after hypoxia. Thus, Rib-1,5-P2 was the major factor increasing the rate of glycolysis during the initial phase of hypoxia. Moreover, we found that Rib-1,5-P2 was synthesized by two steps: the ribose-phosphate pyrophosphokinase (5-phosphoribosyl-1-pyrophosphate synthetase; PRPP synthetase) reaction (EC ) catalyzing the reaction, Rib-5-P + ATP --> PRPP + AMP and a new enzyme, "PRPP pyrophosphatase" catalyzing the reaction, PRPP --> Rib-1,5-P2 + P(i). Both PRPP synthetase and PRPP pyrophosphatase were significantly activated 30 s after hypoxia. Pretreatment with 1-octadecyl-2-methyl-rac-glycero-3-phosphocholine and calphostin C prevented the activation of ribose PRPP synthetase and PRPP pyrophosphatase as well as increase in Rib-1,5-P2 and activation of phosphofructokinase 30 s after hypoxia. These data suggest that the activation of the above enzymes was mediated by protein kinase C acting via activation of phosphatidylinositol specific phospholipase C in the macrophages during hypoxia.
Kawaguchi
T
T
Department of Biochemistry, Dallas Veterans Affairs Medical Center, Dallas, Texas 75216, USA.
Veech
R L
RL
Uyeda
K
K
D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005635:Fructosediphosphates / Q000378:metabolism*; D006358:Hot Temperature; D000860:Hypoxia; D007700:Kinetics; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D009281:Naphthalenes / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D010428:Pentosephosphates / Q000502:physiology*; D010742:Phospholipid Ethers / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D012268:Ribose-Phosphate Pyrophosphokinase / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
D004791:Enzyme Inhibitors; D005635:Fructosediphosphates; D009281:Naphthalenes; D010428:Pentosephosphates; D010742:Phospholipid Ethers; C050562:ribose-1,5-bisphosphate; C026659:edelfosine; D000249:Adenosine Monophosphate; C027652:fructose 2,6-diphosphate; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011493:Protein Kinase C; D012268:Ribose-Phosphate Pyrophosphokinase; C058819:calphostin C; D010100:Oxygen