title: Differences in NGFI-B, Nurr1, and NOR-1 expression and nucleocytoplasmic translocation in glutamate-treated neurons.
abstract: NGFI-B (NR4A1, Nur77 or TR3) together with Nurr1 (NR4A2) and NOR-1 (NR4A3) constitute the NR4A subgroup of orphan nuclear receptors. They play critical roles in proliferation, differentiation, survival and apoptosis in different cell types, including neurons, immature T-cells, and different cancer cells. As ligand-independent and constitutively active receptors, the diverse biological activities of NGFI-B, Nurr1 and NOR-1 depend on their levels of expression, post-translational modifications and subcellular localization. Nuclear localization of the NR4A proteins leads to transcriptional activity, whereas NGFI-B and recently also NOR-1 have been shown to induce apoptosis by a more direct mechanism when localized at mitochondria. In the present study we investigated mRNA expression and subcellular translocation of the NR4A proteins during glutamate excitotoxicity in rat cerebellar granule neurons. NGFI-B and Nurr1 mRNA, but not NOR-1 mRNA, were induced by treatments associated with calcium influx, although their regulation seemed to be different. NR4A(gfp) fusion proteins showed a predominant nuclear localization in untreated cells. After glutamate treatment NGFI-B(gfp) translocated to cytosol and mitochondria within a few hours, whereas Nurr1(gfp) translocation was delayed, and NOR-1(gfp) mainly stayed in the nucleus. Subcellular targeting of NGFI-B seems to be tightly regulated, as a single mutation of threonine 142 altered NGFI-B(gfp) localization. Differences in expression and subcellular translocation of NGFI-B, Nurr1, and NOR-1 may reflect different functions in neurons in glutamate excitotoxicity.
authors.affiliation: Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway. k.b.debernard@farmasi.uio.no
authors.forename: Karen A
authors.initials: KA
authors.lastname: Boldingh Debernard
authors.forename: Gro H
authors.initials: GH
authors.lastname: Mathisen
authors.forename: Ragnhild E
authors.initials: RE
authors.lastname: Paulsen
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000494:pharmacology*; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1 / Q000235:genetics / Q000378:metabolism*; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; C539820:Nr4a1 protein, rat; C539884:Nr4a2 protein, rat; C091333:Nr4a3 protein, rat; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D012333:RNA, Messenger; D018698:Glutamic Acid; D002118:Calcium