Acetylation of human mitochondrial citrate carrier modulates mitochondrial citrate/malate exchange activity to sustain NADPH production during macrophage activation.
The mitochondrial citrate-malate exchanger (CIC), a known target of acetylation, is up-regulated in activated immune cells and plays a key role in the production of inflammatory mediators. However, the role of acetylation in CIC activity is elusive. We show that CIC is acetylated in activated primary human macrophages and U937 cells and the level of acetylation is higher in glucose-deprived compared to normal glucose medium. Acetylation enhances CIC transport activity, leading to a higher citrate efflux from mitochondria in exchange with malate. Cytosolic citrate levels do not increase upon activation of cells grown in deprived compared to normal glucose media, indicating that citrate, transported from mitochondria at higher rates from acetylated CIC, is consumed at higher rates. Malate levels in the cytosol are lower in activated cells grown in glucose-deprived compared to normal glucose medium, indicating that this TCA intermediate is rapidly recycled back into the cytosol where it is used by the malic enzyme. Additionally, in activated cells CIC inhibition increases the NADP+/NADPH ratio in glucose-deprived cells; this ratio is unchanged in glucose-rich grown cells due to the activity of the pentose phosphate pathway. Consistently, the NADPH-producing isocitrate dehydrogenase level is higher in activated glucose-deprived as compared to glucose rich cells. These results demonstrate that, in the absence of glucose, activated macrophages increase CIC acetylation to enhance citrate efflux from mitochondria not only to produce inflammatory mediators but also to meet the NADPH demand through the actions of isocitrate dehydrogenase and malic enzyme.
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy.
Erika M
EM
Palmieri
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy.
Iolanda
I
Spera
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy.
Alessio
A
Menga
Department of Science, University of Basilicata, Potenza, Italy.
Vittoria
V
Infantino
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy.
Vito
V
Porcelli
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy; Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy; CNR Institute of Biomembranes and Bioenergetics, Bari, Italy.
Vito
V
Iacobazzi
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy.
Ciro L
CL
Pierri
Department of Cancer Biology, Thomas Jefferson University, Philadelphia, USA; Department of Neurological Surgery, Thomas Jefferson University, Philadelphia, USA.
Douglas C
DC
Hooper
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy; Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy. Electronic address: ferdinando.palmieri@uniba.it.
Ferdinando
F
Palmieri
Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari "Aldo Moro", Bari, Italy; Center of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, Italy. Electronic address: alessandra.castegna@uniba.it.
Alessandra
A
Castegna
D000107:Acetylation; D001692:Biological Transport; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D019343:Citric Acid / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D007371:Interferon-gamma / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects / Q000502:physiology*; D008293:Malates / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D056566:Sirtuin 3 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D020298:U937 Cells
D002352:Carrier Proteins; D008293:Malates; D014409:Tumor Necrosis Factor-alpha; C020723:citrate-binding transport protein; D019343:Citric Acid; D009249:NADP; C030298:malic acid; D007371:Interferon-gamma; C466093:SIRT3 protein, human; D056566:Sirtuin 3; D005947:Glucose
Acetylation; Citrate; Inflammation; Macrophage; Mitochondrial citrate carrier; Post-translational modification