Acetylation of human mitochondrial citrate carrier modulates mitochondrial citrate/malate exchange activity to sustain NADPH production during macrophage activation

Erika M. Palmieri, Iolanda Spera, Alessio Menga, Vittoria Infantino, Vito Porcelli, Vito Iacobazzi, Ciro L. Pierri, Douglas C. Hooper, Ferdinando Palmieri, Alessandra Castegna

Research output: Contribution to journalArticle

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Abstract

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.

Original languageEnglish
Pages (from-to)729-738
Number of pages10
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1847
Issue number8
DOIs
Publication statusPublished - Apr 24 2015

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Acetylation
Macrophage Activation
Macrophages
NADP
Citric Acid
Ion exchange
Thermodynamic properties
Chemical activation
Glucose
Mitochondria
Isocitrate Dehydrogenase
Cytosol
Cells
malic acid
citrate-binding transport protein
Pentoses
Pentose Phosphate Pathway
U937 Cells
Ion exchangers
Enzymes

Keywords

  • Acetylation
  • Citrate
  • Inflammation
  • Macrophage
  • Mitochondrial citrate carrier
  • Post-translational modification

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology
  • Medicine(all)

Cite this

Acetylation of human mitochondrial citrate carrier modulates mitochondrial citrate/malate exchange activity to sustain NADPH production during macrophage activation. / Palmieri, Erika M.; Spera, Iolanda; Menga, Alessio; Infantino, Vittoria; Porcelli, Vito; Iacobazzi, Vito; Pierri, Ciro L.; Hooper, Douglas C.; Palmieri, Ferdinando; Castegna, Alessandra.

In: Biochimica et Biophysica Acta - Bioenergetics, Vol. 1847, No. 8, 24.04.2015, p. 729-738.

Research output: Contribution to journalArticle

Palmieri, Erika M. ; Spera, Iolanda ; Menga, Alessio ; Infantino, Vittoria ; Porcelli, Vito ; Iacobazzi, Vito ; Pierri, Ciro L. ; Hooper, Douglas C. ; Palmieri, Ferdinando ; Castegna, Alessandra. / Acetylation of human mitochondrial citrate carrier modulates mitochondrial citrate/malate exchange activity to sustain NADPH production during macrophage activation. In: Biochimica et Biophysica Acta - Bioenergetics. 2015 ; Vol. 1847, No. 8. pp. 729-738.
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AU - Palmieri, Erika M.

AU - Spera, Iolanda

AU - Menga, Alessio

AU - Infantino, Vittoria

AU - Porcelli, Vito

AU - Iacobazzi, Vito

AU - Pierri, Ciro L.

AU - Hooper, Douglas C.

AU - Palmieri, Ferdinando

AU - Castegna, Alessandra

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N2 - 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.

AB - 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.

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