title: Hypothyroid phenotype is contributed by mitochondrial complex I inactivation due to translocated neuronal nitric-oxide synthase.
abstract: Although transcriptional effects of thyroid hormones have substantial influence on oxidative metabolism, how thyroid sets basal metabolic rate remains obscure. Compartmental localization of nitric-oxide synthases is important for nitric oxide signaling. We therefore examined liver neuronal nitric-oxide synthase-alpha (nNOS) subcellular distribution as a putative mechanism for thyroid effects on rat metabolic rate. At low 3,3',5-triiodo-L-thyronine levels, nNOS mRNA increased by 3-fold, protein expression by one-fold, and nNOS was selectively translocated to mitochondria without changes in other isoforms. In contrast, under thyroid hormone administration, mRNA level did not change and nNOS remained predominantly localized in cytosol. In hypothyroidism, nNOS translocation resulted in enhanced mitochondrial nitric-oxide synthase activity with low O2 uptake. In this context, NO utilization increased active O2 species and peroxynitrite yields and tyrosine nitration of complex I proteins that reduced complex activity. Hypothyroidism was also associated to high phospho-p38 mitogen-activated protein kinase and decreased phospho-extracellular signal-regulated kinase 1/2 and cyclin D1 levels. Similarly to thyroid hormones, but without changing thyroid status, nitric-oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester increased basal metabolic rate, prevented mitochondrial nitration and complex I derangement, and turned mitogen-activated protein kinase signaling and cyclin D1 expression back to control pattern. We surmise that nNOS spatial confinement in mitochondria is a significant downstream effector of thyroid hormone and hypothyroid phenotype.
authors.affiliation: Laboratory of Oxygen Metabolism, University Hospital, Facultad de Medicina, University of Buenos Aires, 1120-Buenos Aires, Argentina.
authors.forename: María C
authors.initials: MC
authors.lastname: Franco
authors.forename: Valeria G
authors.initials: VG
authors.lastname: Antico Arciuch
authors.forename: Jorge G
authors.initials: JG
authors.lastname: Peralta
authors.forename: Soledad
authors.initials: S
authors.lastname: Galli
authors.forename: Damián
authors.initials: D
authors.lastname: Levisman
authors.forename: Lidia M
authors.initials: LM
authors.lastname: López
authors.forename: Leonardo
authors.initials: L
authors.lastname: Romorini
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Poderoso
authors.forename: María C
authors.initials: MC
authors.lastname: Carreras
mesh_terms: D000818:Animals; D019938:Cyclin D1 / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D042967:Electron Transport Complex I / Q000378:metabolism*; D004583:Electrons; D004591:Electrophoresis, Polyacrylamide Gel; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D007037:Hypothyroidism / Q000378:metabolism / Q000473:pathology*; D015151:Immunoblotting; D047468:Immunoprecipitation; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008297:Male; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D008956:Models, Chemical; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D016877:Oxidants / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000737:chemistry; D010641:Phenotype; D020033:Protein Isoforms; D021381:Protein Transport; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000378:metabolism; D013963:Thyroid Hormones / Q000378:metabolism; D014158:Transcription, Genetic; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D018841:HSP90 Heat-Shock Proteins; D016877:Oxidants; D020033:Protein Isoforms; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D013963:Thyroid Hormones; D019938:Cyclin D1; D030421:Peroxynitrous Acid; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D048051:p38 Mitogen-Activated Protein Kinases; D042967:Electron Transport Complex I; D010100:Oxygen; D019331:NG-Nitroarginine Methyl Ester