title: Continuous expression of HIF-1α in neural stem/progenitor cells.
abstract: Hypoxia-inducible factor-1 alpha subunit (HIF-1α) is a transcriptional activator mediating adaptive cellular response to hypoxia. Normally degraded in most cell types and tissues, HIF-1α becomes stable and transcriptionally active under conditions of hypoxia. In contrast, we found that HIF-1α is continuously expressed in adult brain neurogenic zones, as well as in neural stem/progenitor cells (NSPCs) from the embryonic and post-natal mouse brain. Our in vitro studies suggest that HIF-1α does not undergo typical hydroxylation, ubiquitination, and degradation within NSPCs under normoxic conditions. Based on immunofluorescence and cell fractionation, HIF-1α is primarily sequestered in membranous cytoplasmic structures, identified by immuno-electron microscopy as HIF-1α-bearing vesicles (HBV), which may prevent HIF-1α from degradation within the cytoplasm. HIF-1α shRNAi-mediated knockdown reduced the resistance of NSPCs to hypoxia, and markedly altered the expression levels of Notch-1 and β-catenin, which influence NSPC differentiation. These findings indicate a unique regulation of HIF-1α protein stability in NSPCs, which may have importance in NSPCs properties and function.
authors.affiliation: Department of Neurosurgery, University of New Mexico Health Sciences Center, Albuquerque, 87131-0001, USA. troitbak@salud.unm.edu
authors.forename: Tamara
authors.initials: T
authors.lastname: Roitbak
authors.forename: Zurab
authors.initials: Z
authors.lastname: Surviladze
authors.forename: Lee Anna
authors.initials: LA
authors.lastname: Cunningham
mesh_terms: D000375:Aging / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D055785:Gene Knockdown Techniques; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D058953:Neural Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D055550:Protein Stability / Q000187:drug effects; D034741:RNA, Small Interfering / Q000494:pharmacology
chemical_list: C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering