title: Overexpression of human selenoprotein H in neuronal cells enhances mitochondrial biogenesis and function through activation of protein kinase A, protein kinase B, and cyclic adenosine monophosphate response element-binding protein pathway.
abstract: Mitochondrial biogenesis is activated by nuclear encoded transcription co-activator peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), which is regulated by several upstream factors including protein kinase A and Akt/protein kinase B. We have previously shown that selenoprotein H enhances the levels of nuclear regulators for mitochondrial biogenesis, increases mitochondrial mass and improves mitochondrial respiratory rate, under physiological condition. Furthermore, overexpression of selenoprotein H protects neuronal HT22 cells from ultraviolet B irradiation-induced cell damage by lowering reactive oxygen species production, and inhibiting activation of caspase-3 and -9, as well as p53. The objective of this study is to identify the cell signaling pathways by which selenoprotein H initiates mitochondrial biogenesis. We first confirmed our previous observation that selenoprotein H transfected HT22 cells increased the protein levels of nuclear-encoded mitochondrial biogenesis factors, peroxisome proliferator-activated receptor γ coactivator-1α, nuclear respiratory factor 1 and mitochondrial transcription factor A. We then observed that total and phosphorylation of protein kinase A, Akt/protein kinase B and cyclic adenosine monophosphate response element-binding protein (CREB) were significantly increased in selenoprotein H transfected cells compared to vector transfected HT22 cells. To verify whether the observed stimulating effects on mitochondrial biogenesis pathways are caused by selenoprotein H and mediated through CREB, we knocked down selenoprotein H mRNA level using siRNA and inhibited CREB with napthol AS-E phosphate in selenoprotein H transfected cells and repeated the measurements of the aforementioned biomarkers. Our results revealed that silencing of selenoprotein H not only decreased the protein levels of PGC-1α, nuclear respiratory factor 1 and mitochondrial transcription factor A, but also decreased the total and phosphorylation levels of protein kinase A, protein kinase B, and CREB. Similarly, CREB inhibition reduced CREB activation and PGC-1α protein levels in selenoprotein H transfected cells. Moreover, selenoprotein H transfection increased the activity of mitochondrial complexes and prevented the ultraviolet B induced fall of mitochondrial membrane potential. We conclude that the effects of selenoprotein H on mitochondrial biogenesis and mitochondrial function are probably mediated through protein kinase A-CREB-PGC-1α and Akt/protein kinase B-CREB-PGC-1α pathways.
authors.affiliation: Department of Pharmaceutical Sciences, Biomanufacturing Research Institute and Technological Enterprise (BRITE), College of Art and Sciences, North Carolina Central University, Durham, NC 27707, USA.
authors.forename: Suresh L
authors.initials: SL
authors.lastname: Mehta
authors.forename: Natalia
authors.initials: N
authors.lastname: Mendelev
authors.forename: Santosh
authors.initials: S
authors.lastname: Kumari
authors.forename: P
authors.initials: P
authors.lastname: Andy Li
mesh_terms: D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000528:radiation effects; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D024101:Mitochondrial Proteins / Q000378:metabolism; D063269:Mitochondrial Turnover / Q000235:genetics / Q000528:radiation effects; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D051266:Nuclear Respiratory Factor 1 / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species; D051140:Selenoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics; D014466:Ultraviolet Rays
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D024101:Mitochondrial Proteins; D051266:Nuclear Respiratory Factor 1; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D017382:Reactive Oxygen Species; D051140:Selenoproteins; D014157:Transcription Factors; C422562:mitochondrial transcription factor A; C519118:selenoprotein H, human; D000242:Cyclic AMP; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases