title: Transforming Growth Factor β1-induced Apoptosis in Podocytes via the Extracellular Signal-regulated Kinase-Mammalian Target of Rapamycin Complex 1-NADPH Oxidase 4 Axis.
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 of mTORC1 by 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-mTORactivation. Our data suggest that TGF-β1 increases translation of Nox4 through the Smad-ERK1/2-mTORC1 axis, which is independent 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.
authors.affiliation: From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and ranjan@yonsei.ac.kr.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Das
authors.affiliation: From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and.
authors.forename: Shanhua
authors.initials: S
authors.lastname: Xu
authors.affiliation: From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and.
authors.forename: Tuyet Thi
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and.
authors.forename: Xianglan
authors.initials: X
authors.lastname: Quan
authors.affiliation: From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and.
authors.forename: Seong-Kyung
authors.initials: SK
authors.lastname: Choi
authors.affiliation: From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and.
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: the Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Cheonan 330-721, Republic of Korea.
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Lee
authors.affiliation: From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and.
authors.forename: Seung-Kuy
authors.initials: SK
authors.lastname: Cha
authors.affiliation: From the Department of Physiology, Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon-Do 220-701, Republic of Korea and qsang@yonsei.ac.kr.
authors.forename: Kyu-Sang
authors.initials: KS
authors.lastname: Park
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins; D039642:Eukaryotic Initiation Factors; D020935:MAP Kinase Signaling System; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D050199:Podocytes / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C499527:Eif4ebp1 protein, mouse; D039642:Eukaryotic Initiation Factors; D010750:Phosphoproteins; D017382:Reactive Oxygen Species; D018125:Receptors, Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C422943:Nox4 protein, mouse; C546843:mTOR protein, mouse; D017346:Protein Serine-Threonine Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; C535148:Mapk1 protein, mouse; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000077293:Receptor, Transforming Growth Factor-beta Type I
keywords: ERK; NADPH oxidase; SMAD transcription factor; TGF-β; apoptosis; mammalian target of rapamycin (mTOR); podocyte; reactive oxygen species (ROS)