title: Mutant HFE H63D protein is associated with prolonged endoplasmic reticulum stress and increased neuronal vulnerability.
abstract: A specific polymorphism in the hemochromatosis (HFE) gene, H63D, is over-represented in neurodegenerative disorders such as amyotrophic lateral sclerosis and Alzheimer disease. Mutations of HFE are best known as being associated with cellular iron overload, but the mechanism by which HFE H63D might increase the risk of neuron degeneration is unclear. Here, using an inducible expression cell model developed from a human neuronal cell line SH-SY5Y, we reported that the presence of the HFE H63D protein activated the unfolded protein response (UPR). This response was followed by a persistent endoplasmic reticulum (ER) stress, as the signals of UPR sensors attenuated and followed by up-regulation of caspase-3 cleavage and activity. Our in vitro findings were recapitulated in a transgenic mouse model carrying Hfe H67D, the mouse equivalent of the human H63D mutation. In this model, UPR activation was detected in the lumbar spinal cord at 6 months then declined at 12 months in association with increased caspase-3 cleavage. Moreover, upon the prolonged ER stress, the number of cells expressing HFE H63D in early apoptosis was increased moderately. Cell proliferation was decreased without increased cell death. Additionally, despite increased iron level in cells carrying HFE H63D, it appeared that ER stress was not responsive to the change of cellular iron status. Overall, our studies indicate that the HFE H63D mutant protein is associated with prolonged ER stress and chronically increased neuronal vulnerability.
authors.affiliation: Department of Neurosurgery, Pennsylvania State University, Milton S. Hershey Medical Center, Hershey, Pennsylvania 17033, USA. yliu2@hmc.psu.edu
authors.forename: Yiting
authors.initials: Y
authors.lastname: Liu
authors.forename: Sang Y
authors.initials: SY
authors.lastname: Lee
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Neely
authors.forename: Wint
authors.initials: W
authors.lastname: Nandar
authors.forename: Mthabisi
authors.initials: M
authors.lastname: Moyo
authors.forename: Zachary
authors.initials: Z
authors.lastname: Simmons
authors.forename: James R
authors.initials: JR
authors.lastname: Connor
mesh_terms: D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D020125:Mutation, Missense; D009474:Neurons / Q000378:metabolism*; D056811:Unfolded Protein Response
chemical_list: C103673:HFE protein, human; D000071020:Hemochromatosis Protein; C499535:Hfe protein, mouse; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D007501:Iron