Iron depletion suppresses mTORC1-directed signalling in intestinal Caco-2 cells via induction of REDD

Ailsa Watson, Christopher Lipina, Harry J. McArdle, Peter M. Taylor, Harinder Hundal (Lead / Corresponding author)

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Abstract

Iron is an indispensable micronutrient that regulates many aspects of cell function, including growth and proliferation. These processes are critically dependent upon signalling via the mammalian or mechanistic target of rapamycin complex 1 (mTORC1). Herein, we test whether iron depletion induced by cell incubation with the iron chelator, deferoxamine (DFO), mediates its effects on cell growth through mTORC1-directed signalling and protein synthesis. We have used Caco-2 cells, a well-established in vitro model of human intestinal epithelia. Iron dpeletion increased expression of iron-regulated proteins (TfR, transferrin receptor and DMT1, divalent metal transporter, as predicted, but it also promoted a marked reduction in growth and proliferation of Caco-2 cells. This was strongly associated with suppressed mTORC1 signalling, as judged by reduced phosphorylation of mTOR substrates, S6K1 and 4E-BP1, and diminished protein synthesis. The reduction in mTORC1 signalling was tightly coupled with increased expression and accumulation of REDD1 (regulated in DNA damage and development 1) and reduced phosphorylation of Akt and TSC2. The increase in REDD1 abundance was rapidly reversed upon iron repletion of cells but was also attenuated by inhibitors of gene transcription, protein phosphatase 2 A (PP2A) and by REDD1 siRNA – strategies that also antagonised the loss in mTORC1 signalling associated with iron depletion. Our findings implicate REDD1 and PP2A as crucial regulators of mTORC1 activity in iron-depleted cells and indicate that their modulation may help mitigate atrophy of the intestinal mucosa that may occur in response to iron deficiency.
Original languageEnglish
Pages (from-to)412-424
JournalCellular Signalling
Volume28
Issue number5
Early online date29 Jan 2016
DOIs
Publication statusPublished - May 2016

Fingerprint

Caco-2 Cells
Iron
DNA Damage
Protein Phosphatase 2
Intestinal Mucosa
Proteins
Growth
Phosphorylation
mechanistic target of rapamycin complex 1
Transferrin Receptors
Deferoxamine
Micronutrients
Chelating Agents
Small Interfering RNA
Atrophy
Metals

Keywords

  • S6K1
  • 4E-BP1
  • Akt
  • PP2A
  • TSC2
  • rheb
  • Deferoxamine

Cite this

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title = "Iron depletion suppresses mTORC1-directed signalling in intestinal Caco-2 cells via induction of REDD",
abstract = "Iron is an indispensable micronutrient that regulates many aspects of cell function, including growth and proliferation. These processes are critically dependent upon signalling via the mammalian or mechanistic target of rapamycin complex 1 (mTORC1). Herein, we test whether iron depletion induced by cell incubation with the iron chelator, deferoxamine (DFO), mediates its effects on cell growth through mTORC1-directed signalling and protein synthesis. We have used Caco-2 cells, a well-established in vitro model of human intestinal epithelia. Iron dpeletion increased expression of iron-regulated proteins (TfR, transferrin receptor and DMT1, divalent metal transporter, as predicted, but it also promoted a marked reduction in growth and proliferation of Caco-2 cells. This was strongly associated with suppressed mTORC1 signalling, as judged by reduced phosphorylation of mTOR substrates, S6K1 and 4E-BP1, and diminished protein synthesis. The reduction in mTORC1 signalling was tightly coupled with increased expression and accumulation of REDD1 (regulated in DNA damage and development 1) and reduced phosphorylation of Akt and TSC2. The increase in REDD1 abundance was rapidly reversed upon iron repletion of cells but was also attenuated by inhibitors of gene transcription, protein phosphatase 2 A (PP2A) and by REDD1 siRNA – strategies that also antagonised the loss in mTORC1 signalling associated with iron depletion. Our findings implicate REDD1 and PP2A as crucial regulators of mTORC1 activity in iron-depleted cells and indicate that their modulation may help mitigate atrophy of the intestinal mucosa that may occur in response to iron deficiency.",
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author = "Ailsa Watson and Christopher Lipina and McArdle, {Harry J.} and Taylor, {Peter M.} and Harinder Hundal",
note = "This work was supported by grants from the Biotechnology and Biological Science Research Council (BB/I007261/1 and BB/N002342/1) and The Scottish Government's Rural and Environment Science and Analytical Services Division (RESAS 854/11).",
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Iron depletion suppresses mTORC1-directed signalling in intestinal Caco-2 cells via induction of REDD. / Watson, Ailsa; Lipina, Christopher; McArdle, Harry J.; Taylor, Peter M.; Hundal, Harinder (Lead / Corresponding author).

In: Cellular Signalling, Vol. 28, No. 5, 05.2016, p. 412-424.

Research output: Contribution to journalArticle

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T1 - Iron depletion suppresses mTORC1-directed signalling in intestinal Caco-2 cells via induction of REDD

AU - Watson, Ailsa

AU - Lipina, Christopher

AU - McArdle, Harry J.

AU - Taylor, Peter M.

AU - Hundal, Harinder

N1 - This work was supported by grants from the Biotechnology and Biological Science Research Council (BB/I007261/1 and BB/N002342/1) and The Scottish Government's Rural and Environment Science and Analytical Services Division (RESAS 854/11).

PY - 2016/5

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N2 - Iron is an indispensable micronutrient that regulates many aspects of cell function, including growth and proliferation. These processes are critically dependent upon signalling via the mammalian or mechanistic target of rapamycin complex 1 (mTORC1). Herein, we test whether iron depletion induced by cell incubation with the iron chelator, deferoxamine (DFO), mediates its effects on cell growth through mTORC1-directed signalling and protein synthesis. We have used Caco-2 cells, a well-established in vitro model of human intestinal epithelia. Iron dpeletion increased expression of iron-regulated proteins (TfR, transferrin receptor and DMT1, divalent metal transporter, as predicted, but it also promoted a marked reduction in growth and proliferation of Caco-2 cells. This was strongly associated with suppressed mTORC1 signalling, as judged by reduced phosphorylation of mTOR substrates, S6K1 and 4E-BP1, and diminished protein synthesis. The reduction in mTORC1 signalling was tightly coupled with increased expression and accumulation of REDD1 (regulated in DNA damage and development 1) and reduced phosphorylation of Akt and TSC2. The increase in REDD1 abundance was rapidly reversed upon iron repletion of cells but was also attenuated by inhibitors of gene transcription, protein phosphatase 2 A (PP2A) and by REDD1 siRNA – strategies that also antagonised the loss in mTORC1 signalling associated with iron depletion. Our findings implicate REDD1 and PP2A as crucial regulators of mTORC1 activity in iron-depleted cells and indicate that their modulation may help mitigate atrophy of the intestinal mucosa that may occur in response to iron deficiency.

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KW - PP2A

KW - TSC2

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KW - Deferoxamine

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DO - 10.1016/j.cellsig.2016.01.014

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VL - 28

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SN - 0898-6568

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