Evidence for Pipecolate Oxidase in Mediating Protection Against Hydrogen Peroxide Stress

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Abstract

Pipecolate, an intermediate of the lysine catabolic pathway, is oxidized to Δ1-piperideine-6-carboxylate (P6C) by the flavoenzyme l-pipecolate oxidase (PIPOX). P6C spontaneously hydrolyzes to generate α-aminoadipate semialdehyde, which is then converted into α-aminoadipate acid by α-aminoadipatesemialdehyde dehydrogenase. l-pipecolate was previously reported to protect mammalian cells against oxidative stress. Here, we examined whether PIPOX is involved in the mechanism of pipecolate stress protection. Knockdown of PIPOX by small interference RNA abolished pipecolate protection against hydrogen peroxide-induced cell death in HEK293 cells suggesting a critical role for PIPOX. Subcellular fractionation analysis showed that PIPOX is localized in the mitochondria of HEK293 cells consistent with its role in lysine catabolism. Signaling pathways potentially involved in pipecolate protection were explored by treating cells with small molecule inhibitors. Inhibition of both mTORC1 and mTORC2 kinase complexes or inhibition of Akt kinase alone blocked pipecolate protection suggesting the involvement of these signaling pathways. Phosphorylation of the Akt downstream target, forkhead transcription factor O3 (FoxO3), was also significantly increased in cells treated with pipecolate, further implicating Akt in the protective mechanism and revealing FoxO3 inhibition as a potentially key step. The results presented here demonstrate that pipecolate metabolism can influence cell signaling during oxidative stress to promote cell survival and suggest that the mechanism of pipecolate protection parallels that of proline, which is also metabolized in the mitochondria. J. Cell. Biochem. 118: 1678–1688, 2017.

Original languageEnglish (US)
Pages (from-to)1678-1688
Number of pages11
JournalJournal of Cellular Biochemistry
Volume118
Issue number7
DOIs
StatePublished - Jul 2017

Fingerprint

Hydrogen Peroxide
Mitochondria
Oxidative stress
HEK293 Cells
Lysine
Oxidative Stress
Phosphotransferases
Cells
Cell signaling
Forkhead Transcription Factors
Phosphorylation
Cell death
Fractionation
RNA Interference
Proline
Metabolism
Cell Survival
Oxidoreductases
Cell Death
L-pipecolate dehydrogenase

Keywords

  • AMINO ACID METABOLISM
  • MITOCHONDRIA
  • OXIDATIVE STRESS
  • PIPECOLATE
  • PIPECOLATE OXIDASE

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

@article{88507bbbd4254d848b23db9016a1a7ce,
title = "Evidence for Pipecolate Oxidase in Mediating Protection Against Hydrogen Peroxide Stress",
abstract = "Pipecolate, an intermediate of the lysine catabolic pathway, is oxidized to Δ1-piperideine-6-carboxylate (P6C) by the flavoenzyme l-pipecolate oxidase (PIPOX). P6C spontaneously hydrolyzes to generate α-aminoadipate semialdehyde, which is then converted into α-aminoadipate acid by α-aminoadipatesemialdehyde dehydrogenase. l-pipecolate was previously reported to protect mammalian cells against oxidative stress. Here, we examined whether PIPOX is involved in the mechanism of pipecolate stress protection. Knockdown of PIPOX by small interference RNA abolished pipecolate protection against hydrogen peroxide-induced cell death in HEK293 cells suggesting a critical role for PIPOX. Subcellular fractionation analysis showed that PIPOX is localized in the mitochondria of HEK293 cells consistent with its role in lysine catabolism. Signaling pathways potentially involved in pipecolate protection were explored by treating cells with small molecule inhibitors. Inhibition of both mTORC1 and mTORC2 kinase complexes or inhibition of Akt kinase alone blocked pipecolate protection suggesting the involvement of these signaling pathways. Phosphorylation of the Akt downstream target, forkhead transcription factor O3 (FoxO3), was also significantly increased in cells treated with pipecolate, further implicating Akt in the protective mechanism and revealing FoxO3 inhibition as a potentially key step. The results presented here demonstrate that pipecolate metabolism can influence cell signaling during oxidative stress to promote cell survival and suggest that the mechanism of pipecolate protection parallels that of proline, which is also metabolized in the mitochondria. J. Cell. Biochem. 118: 1678–1688, 2017.",
keywords = "AMINO ACID METABOLISM, MITOCHONDRIA, OXIDATIVE STRESS, PIPECOLATE, PIPECOLATE OXIDASE",
author = "Natarajan, {Sathish K} and Ezhumalai Muthukrishnan and Oleh Khalimonchuk and Mott, {Justin L} and Becker, {Donald F}",
year = "2017",
month = "7",
doi = "10.1002/jcb.25825",
language = "English (US)",
volume = "118",
pages = "1678--1688",
journal = "Journal of Cellular Biochemistry",
issn = "0730-2312",
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number = "7",

}

TY - JOUR

T1 - Evidence for Pipecolate Oxidase in Mediating Protection Against Hydrogen Peroxide Stress

AU - Natarajan, Sathish K

AU - Muthukrishnan, Ezhumalai

AU - Khalimonchuk, Oleh

AU - Mott, Justin L

AU - Becker, Donald F

PY - 2017/7

Y1 - 2017/7

N2 - Pipecolate, an intermediate of the lysine catabolic pathway, is oxidized to Δ1-piperideine-6-carboxylate (P6C) by the flavoenzyme l-pipecolate oxidase (PIPOX). P6C spontaneously hydrolyzes to generate α-aminoadipate semialdehyde, which is then converted into α-aminoadipate acid by α-aminoadipatesemialdehyde dehydrogenase. l-pipecolate was previously reported to protect mammalian cells against oxidative stress. Here, we examined whether PIPOX is involved in the mechanism of pipecolate stress protection. Knockdown of PIPOX by small interference RNA abolished pipecolate protection against hydrogen peroxide-induced cell death in HEK293 cells suggesting a critical role for PIPOX. Subcellular fractionation analysis showed that PIPOX is localized in the mitochondria of HEK293 cells consistent with its role in lysine catabolism. Signaling pathways potentially involved in pipecolate protection were explored by treating cells with small molecule inhibitors. Inhibition of both mTORC1 and mTORC2 kinase complexes or inhibition of Akt kinase alone blocked pipecolate protection suggesting the involvement of these signaling pathways. Phosphorylation of the Akt downstream target, forkhead transcription factor O3 (FoxO3), was also significantly increased in cells treated with pipecolate, further implicating Akt in the protective mechanism and revealing FoxO3 inhibition as a potentially key step. The results presented here demonstrate that pipecolate metabolism can influence cell signaling during oxidative stress to promote cell survival and suggest that the mechanism of pipecolate protection parallels that of proline, which is also metabolized in the mitochondria. J. Cell. Biochem. 118: 1678–1688, 2017.

AB - Pipecolate, an intermediate of the lysine catabolic pathway, is oxidized to Δ1-piperideine-6-carboxylate (P6C) by the flavoenzyme l-pipecolate oxidase (PIPOX). P6C spontaneously hydrolyzes to generate α-aminoadipate semialdehyde, which is then converted into α-aminoadipate acid by α-aminoadipatesemialdehyde dehydrogenase. l-pipecolate was previously reported to protect mammalian cells against oxidative stress. Here, we examined whether PIPOX is involved in the mechanism of pipecolate stress protection. Knockdown of PIPOX by small interference RNA abolished pipecolate protection against hydrogen peroxide-induced cell death in HEK293 cells suggesting a critical role for PIPOX. Subcellular fractionation analysis showed that PIPOX is localized in the mitochondria of HEK293 cells consistent with its role in lysine catabolism. Signaling pathways potentially involved in pipecolate protection were explored by treating cells with small molecule inhibitors. Inhibition of both mTORC1 and mTORC2 kinase complexes or inhibition of Akt kinase alone blocked pipecolate protection suggesting the involvement of these signaling pathways. Phosphorylation of the Akt downstream target, forkhead transcription factor O3 (FoxO3), was also significantly increased in cells treated with pipecolate, further implicating Akt in the protective mechanism and revealing FoxO3 inhibition as a potentially key step. The results presented here demonstrate that pipecolate metabolism can influence cell signaling during oxidative stress to promote cell survival and suggest that the mechanism of pipecolate protection parallels that of proline, which is also metabolized in the mitochondria. J. Cell. Biochem. 118: 1678–1688, 2017.

KW - AMINO ACID METABOLISM

KW - MITOCHONDRIA

KW - OXIDATIVE STRESS

KW - PIPECOLATE

KW - PIPECOLATE OXIDASE

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DO - 10.1002/jcb.25825

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C2 - 27922192

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VL - 118

SP - 1678

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JO - Journal of Cellular Biochemistry

JF - Journal of Cellular Biochemistry

SN - 0730-2312

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