Transient expression of Nxf, a bHLH-PAS transactivator induced by neuronal preconditioning, confers neuroprotection in cultured cells.
Cortical spreading depression (CSD) induces waves of neuronal depolarization that confer neuroprotection to subsequent ischemic events in the rat brain. To gain insights into the molecular mechanisms elicited by CSD, we used representational difference analysis (RDA) to identify mRNAs induced by potassium depolarization in vivo. Using this approach, we have isolated a cDNA encoding the SIM2-related bHLH-PAS protein Nxf. Our results confirm that Nxf mRNA and protein are rapidly and transiently expressed in cortical neurons following CSD. Reporter assays show that Nxf is a transcriptional activator that associates with the bHLH-PAS sub-class co-factor ARNT2. Adenovirus-mediated expression of epitope-tagged Nxf results in cell death and the direct activation of the Bax gene in cultured cells. However, RNA interference studies show that endogenous Nxf is required for optimal neuroprotection by preconditioning in cultured F-11 cells. Together, our data indicate that Nxf is a novel bHLH-PAS transactivator transiently induced by preconditioning and that its sustained expression is detrimental. The identification of Nxf may represent an important step in our understanding of the molecular mechanisms of brain preconditioning and injury.
Hester
Ian
I
University of Ottawa, Department of Cellular and Molecular Medicine, Ottawa, ON, Canada.
McKee
Sarah
S
Pelletier
Phillip
P
Thompson
Charles
C
Storbeck
Christopher
C
Mears
Alan
A
Schulz
Jörg B
JB
Hakim
Antoine A
AA
Sabourin
Luc A
LA
D000818:Animals; D000831:Animals, Newborn; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000187:drug effects; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D013181:Cortical Spreading Depression / Q000187:drug effects / Q000502:physiology*; D005727:Ganglia, Spinal / Q000166:cytology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D051379:Mice; D009447:Neuroblastoma; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D013997:Time Factors; D015534:Trans-Activators / Q000502:physiology; D014162:Transfection / Q000379:methods; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D051792:Basic Helix-Loop-Helix Proteins; D010751:Phosphopyruvate Hydratase; D011188:Potassium; D015534:Trans-Activators; D051028:bcl-2-Associated X Protein; C490991:Arnt2 protein, rat; C516513:Npas4 protein, rat