Nox4 mediates TGF-beta1-induced retinoblastoma protein phosphorylation, proliferation, and hypertrophy in human airway smooth muscle cells.
Transforming growth factor-beta1 (TGF-beta1) plays a pivotal role in increasing airway smooth muscle mass in severe asthma by inducing proliferation and hypertrophy of human airway smooth muscle. The mechanism(s) for these effects of TGF-beta1 have not been fully elucidated. In this study, we demonstrate that TGF-beta1 is a potent inducer of expression of the nonphagocyte NAD(P)H oxidase catalytic homolog Nox4, diphenylene iodonium-inhibitable reactive oxygen species production, proliferation, and hypertrophy in cultured human airway smooth muscle cells. By confocal microscopy, TGF-beta1-induced Nox4 was localized with the endoplasmic reticulum and the nucleus, implying a role for Nox4 in regulation of both the cell cycle and protein synthesis. Consistent with this hypothesis, TGF-beta1 increased retinoblastoma protein phosphorylation at both Ser807/811 and Ser780. Silencing Nox4 prevented TGF-beta1-mediated retinoblastoma protein phosphorylation, proliferation, and cell hypertrophy. TGF-beta1 also increased phosphorylation of eukaryotic translation initiation factor 4E binding protein-1 at Thr37/46, and this was likewise blocked by silencing Nox4. This is the first report to suggest a functional role for Nox4 in cell cycle transition and to demonstrate that Nox4 influences the pathobiochemistry of asthma by generating reactive oxygen species that promote TGF-beta1-induced proliferation and hypertrophy of human airway smooth muscle.
Sturrock
Anne
A
Division of Respiratory, Critical Care and Occupational Pulmonary Medicine, University of Utah Health Sciences Center and Veterans Administration Medical Center, Salt Lake City, Utah 84132, USA.
Huecksteadt
Thomas P
TP
Norman
Kimberly
K
Sanders
Karl
K
Murphy
Thomas M
TM
Chitano
Pasquale
P
Wilson
Kimberly
K
Hoidal
John R
JR
Kennedy
Thomas P
TP
D028341:Activins / Q000378:metabolism / Q000494:pharmacology; D001249:Asthma / Q000378:metabolism* / Q000473:pathology; D001980:Bronchi / Q000166:cytology*; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002467:Cell Nucleus / Q000201:enzymology; D002478:Cells, Cultured; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D006801:Humans; D006984:Hypertrophy; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000502:physiology; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D051900:Smad3 Protein / Q000378:metabolism; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000378:metabolism* / Q000494:pharmacology
D039561:Eukaryotic Initiation Factor-4E; D016271:Proto-Oncogene Proteins c-myc; D017382:Reactive Oxygen Species; D016160:Retinoblastoma Protein; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; C422405:activin A; D028341:Activins; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; D019869:Phosphatidylinositol 3-Kinases; D016203:CDC2 Protein Kinase