Transforming growth factor β1-induced apoptosis in podocytes via the extracellular signal-regulated kinase- mammalian target of rapamycin complex 1-nadph oxidase 4 axis

Ranjan Das, Shanhua Xu, Tuyet Thi Nguyen, Xianglan Quan, Seong Kyung Choi, Soo Jin Kim, Eun Young Lee, Seungkuy Cha, Kyusang Park

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

TGF-β is a pleiotropic cytokine that accumulates during kidney injuries, resulting in various renal diseases. We have reported previously that TGF-β1 induces the selective up-regulation of mitochondrial Nox4, playing critical roles in podocyte apoptosis. Here we investigated the regulatory mechanism of Nox4 up-regulation by mTORC1 activation on TGF-β1-induced apoptosis in immortalized podocytes. TGF-β1 treatment markedly increased the phosphorylation of mammalian target of rapamycin (mTOR) and its downstream targets p70S6K and 4EBP1. Blocking TGF-β receptor I with SB431542 completely blunted the phosphorylation of mTOR, p70S6K, and 4EBP1. Transient adenoviral overexpression of mTOR-WT and constitutively active mTORΔ augmented TGF-β1-treated Nox4 expression, reactive oxygen species (ROS) generation, and apoptosis, whereas mTOR kinase-dead suppressed the above changes. In addition, knockdown of mTOR mimicked the effect of mTOR-KD. Inhibition ofmTORC1by low-dose rapamycin or knockdown of p70S6K protected podocytes through attenuation of Nox4 expression and subsequent oxidative stress-induced apoptosis by TGF-β1. Pharmacological inhibition of the MEK-ERK cascade, but not the PI3K-Akt-TSC2 pathway, abolished TGF-β1-induced mTOR activation. Inhibition of either ERK1/2 or mTORC1 did not reduce the TGF-β1-stimulated increase in Nox4 mRNA level but significantly inhibited total Nox4 expression, ROS generation, and apoptosis induced by TGF-β1. Moreover, double knockdown of Smad2 and 3 or only Smad4 completely suppressed TGF-β1-induced ERK1/2-mTOR activation. Our data suggest that TGF-β1 increases translation ofNox4throughtheSmad-ERK1/2-mTORC1axis,whichisindependent of transcriptional regulation. Activation of this pathway plays a crucial role in ROS generation and mitochondrial dysfunction, leading to podocyte apoptosis. Therefore, inhibition of the ERK1/2-mTORC1 pathway could be a potential therapeutic and preventive target in proteinuric and chronic kidney diseases.

Original languageEnglish
Pages (from-to)30830-30842
Number of pages13
JournalJournal of Biological Chemistry
Volume290
Issue number52
DOIs
Publication statusPublished - 2015 Dec 25

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Podocytes
Extracellular Signal-Regulated MAP Kinases
Transforming Growth Factors
Sirolimus
Oxidoreductases
Apoptosis
70-kDa Ribosomal Protein S6 Kinases
Chemical activation
Reactive Oxygen Species
Phosphorylation
Up-Regulation
mechanistic target of rapamycin complex 1
Kidney
Oxidative stress
MAP Kinase Signaling System
Mitogen-Activated Protein Kinase Kinases
Phosphatidylinositol 3-Kinases
Chronic Renal Insufficiency
Oxidative Stress
Phosphotransferases

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Das, Ranjan ; Xu, Shanhua ; Nguyen, Tuyet Thi ; Quan, Xianglan ; Choi, Seong Kyung ; Kim, Soo Jin ; Lee, Eun Young ; Cha, Seungkuy ; Park, Kyusang. / Transforming growth factor β1-induced apoptosis in podocytes via the extracellular signal-regulated kinase- mammalian target of rapamycin complex 1-nadph oxidase 4 axis. In: Journal of Biological Chemistry. 2015 ; Vol. 290, No. 52. pp. 30830-30842.
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Transforming growth factor β1-induced apoptosis in podocytes via the extracellular signal-regulated kinase- mammalian target of rapamycin complex 1-nadph oxidase 4 axis. / Das, Ranjan; Xu, Shanhua; Nguyen, Tuyet Thi; Quan, Xianglan; Choi, Seong Kyung; Kim, Soo Jin; Lee, Eun Young; Cha, Seungkuy; Park, Kyusang.

In: Journal of Biological Chemistry, Vol. 290, No. 52, 25.12.2015, p. 30830-30842.

Research output: Contribution to journalArticle

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T1 - Transforming growth factor β1-induced apoptosis in podocytes via the extracellular signal-regulated kinase- mammalian target of rapamycin complex 1-nadph oxidase 4 axis

AU - Das, Ranjan

AU - Xu, Shanhua

AU - Nguyen, Tuyet Thi

AU - Quan, Xianglan

AU - Choi, Seong Kyung

AU - Kim, Soo Jin

AU - Lee, Eun Young

AU - Cha, Seungkuy

AU - Park, Kyusang

PY - 2015/12/25

Y1 - 2015/12/25

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AB - TGF-β is a pleiotropic cytokine that accumulates during kidney injuries, resulting in various renal diseases. We have reported previously that TGF-β1 induces the selective up-regulation of mitochondrial Nox4, playing critical roles in podocyte apoptosis. Here we investigated the regulatory mechanism of Nox4 up-regulation by mTORC1 activation on TGF-β1-induced apoptosis in immortalized podocytes. TGF-β1 treatment markedly increased the phosphorylation of mammalian target of rapamycin (mTOR) and its downstream targets p70S6K and 4EBP1. Blocking TGF-β receptor I with SB431542 completely blunted the phosphorylation of mTOR, p70S6K, and 4EBP1. Transient adenoviral overexpression of mTOR-WT and constitutively active mTORΔ augmented TGF-β1-treated Nox4 expression, reactive oxygen species (ROS) generation, and apoptosis, whereas mTOR kinase-dead suppressed the above changes. In addition, knockdown of mTOR mimicked the effect of mTOR-KD. Inhibition ofmTORC1by low-dose rapamycin or knockdown of p70S6K protected podocytes through attenuation of Nox4 expression and subsequent oxidative stress-induced apoptosis by TGF-β1. Pharmacological inhibition of the MEK-ERK cascade, but not the PI3K-Akt-TSC2 pathway, abolished TGF-β1-induced mTOR activation. Inhibition of either ERK1/2 or mTORC1 did not reduce the TGF-β1-stimulated increase in Nox4 mRNA level but significantly inhibited total Nox4 expression, ROS generation, and apoptosis induced by TGF-β1. Moreover, double knockdown of Smad2 and 3 or only Smad4 completely suppressed TGF-β1-induced ERK1/2-mTOR activation. Our data suggest that TGF-β1 increases translation ofNox4throughtheSmad-ERK1/2-mTORC1axis,whichisindependent of transcriptional regulation. Activation of this pathway plays a crucial role in ROS generation and mitochondrial dysfunction, leading to podocyte apoptosis. Therefore, inhibition of the ERK1/2-mTORC1 pathway could be a potential therapeutic and preventive target in proteinuric and chronic kidney diseases.

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