title: Expression of poly(C)-binding proteins is differentially regulated by hypoxia and ischemia in cortical neurons.
abstract: Hypoxia and ischemia regulate the expression of several important genes at the level of transcription and of mRNA stability. Two isoforms of a 40-kDa poly(C)-binding protein, previously identified as RNA-binding proteins, bind to a hypoxia-inducible protein-binding site in the 3'-untranslated region of erythropoietin and tyrosine hydroxylase mRNAs and regulate mRNA stability. To determine if poly(C)-binding proteins show changes in expression -- which might regulate mRNA stability -- in hypoxic or ischemic neuronal cells, we examined poly(C)-binding protein 1 and poly(C)-binding protein 2 expression in hypoxic cortical neuron cultures and in rat cerebral cortex after focal ischemia. Reverse transcription-polymerase chain reaction and western blotting showed hypoxic up-regulation of poly(C)-binding protein 1, and down-regulation of poly(C)-binding protein 2, mRNA and protein expression. Hypoxia-inducible expression of poly(C)-binding protein 1 was mediated by p38 mitogen-activated protein kinase, while hypoxia-reducible expression of poly(C)-binding protein 2 was mediated by protein kinase C. Immunostaining showed that poly(C)-binding protein 1, but not poly(C)-binding protein 2, expression was increased in the ischemic boundary zone (penumbra) of the frontal cortex after 90 min of ischemia, and persisted for at least 72 h after reperfusion. These results demonstrate that poly(C)-binding protein 1 and poly(C)-binding protein 2 in cortical neurons are differentially affected by hypoxic/ischemic insults, suggesting that there are functional differences between poly(C)-binding protein isoforms. Since we observed no poly(C)-binding protein expression in astroglia, alternative mRNA stability mechanisms may exist in these cells.
authors.affiliation: Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, CA 94945-0638, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhu
authors.forename: Y
authors.initials: Y
authors.lastname: Sun
authors.forename: X O
authors.initials: XO
authors.lastname: Mao
authors.forename: K L
authors.initials: KL
authors.lastname: Jin
authors.forename: D A
authors.initials: DA
authors.lastname: Greenberg
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism* / Q000503:physiopathology; D004268:DNA-Binding Proteins; D015536:Down-Regulation / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D016716:PC12 Cells; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014157:Transcription Factors; D015854:Up-Regulation / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C094604:PCBP1 protein, human; C501903:PCBP2 protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases