Biomaterial Database

Alterations in the interaction between iron regulatory proteins and their iron responsive element in normal and Alzheimer's diseased brains. 2000

D J Piñero, and J Hu, and J R Connor

Department of Neuroscience and Anatomy, Penn State University College of Medicine, M.S. Hershey Medical Center, PA 17033, USA.

Iron regulatory proteins (IRPs) are cytoplasmic mRNA binding proteins involved in intracellular regulation of iron homeostasis. IRPs regulate expression of ferritin and transferrin receptor at the mRNA level by interacting with a conserved RNA structure termed the iron-responsive element (IRE). This concordant regulation of transferrin receptors and ferritin is designed so a cell can obtain iron when it is needed, and sequester iron when it is in excess. However, we have reported that iron accumulates in the brain in Alzheimer's disease without a concomitant increase in ferritin. An increase in iron without proper sequestration can increase the vulnerability of cells to oxidative stress. Oxidative stress is a component of many neurological diseases including Alzheimer's. We hypothesized that alterations in the IRP/IRE interaction could be the site at which iron mismanagement occurs in the Alzheimer's brains. In this report we demonstrate that in normal human brain extracts, the IRP is detected as a double IRE/IRP complex by RNA band shift assay, but in 2 of 6 Alzheimer's brain (AD) extracts examined a single IRE/IRP complex was obtained. Furthermore, the mobility of the single IRE/IRP complex in Alzheimer's brain extracts is decreased relative to the double IRE/IRP complex. Western blot and RNA band super shift assay demonstrate that IRP1 is involved in the formation of the single IRE/IRP complex. In vitro analyses suggest that the stability of the doublet complex and single AD complex are different. The single complex from the AD brain are more stable. A more stable IRE/IRP complex in the AD brain could increase stability of the transferrin receptor mRNA and inhibit ferritin synthesis. At the cellular level, the outcome of this alteration in the molecular regulatory mechanism would be increased iron accumulation without an increase in ferritin; identical to the observation we reported in AD brains. The appearance of the single IRE/IRP complex in Alzheimer's brain extracts is associated with relatively high endogenous ribonuclease activity. We propose that elevated RNase activity is one mechanism by which the iron regulatory system becomes dysfunctional.

UI	MeSH Term	Description	Entries
D007506	Iron-Sulfur Proteins	A group of proteins possessing only the iron-sulfur complex as the prosthetic group. These proteins participate in all major pathways of electron transport: photosynthesis, respiration, hydroxylation and bacterial hydrogen and nitrogen fixation.	Iron-Sulfur Protein,Iron Sulfur Proteins,Iron Sulfur Protein,Protein, Iron-Sulfur,Proteins, Iron Sulfur,Proteins, Iron-Sulfur,Sulfur Proteins, Iron
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D011990	Receptors, Transferrin	Membrane glycoproteins found in high concentrations on iron-utilizing cells. They specifically bind iron-bearing transferrin, are endocytosed with its ligand and then returned to the cell surface where transferrin without its iron is released.	Transferrin Receptors,Transferrin Receptor,Receptor, Transferrin
D001921	Brain	The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.	Encephalon
D001932	Brain Neoplasms	Neoplasms of the intracranial components of the central nervous system, including the cerebral hemispheres, basal ganglia, hypothalamus, thalamus, brain stem, and cerebellum. Brain neoplasms are subdivided into primary (originating from brain tissue) and secondary (i.e., metastatic) forms. Primary neoplasms are subdivided into benign and malignant forms. In general, brain tumors may also be classified by age of onset, histologic type, or presenting location in the brain.	Brain Cancer,Brain Metastases,Brain Tumors,Cancer of Brain,Malignant Primary Brain Tumors,Neoplasms, Intracranial,Benign Neoplasms, Brain,Brain Neoplasm, Primary,Brain Neoplasms, Benign,Brain Neoplasms, Malignant,Brain Neoplasms, Malignant, Primary,Brain Neoplasms, Primary Malignant,Brain Tumor, Primary,Brain Tumor, Recurrent,Cancer of the Brain,Intracranial Neoplasms,Malignant Neoplasms, Brain,Malignant Primary Brain Neoplasms,Neoplasms, Brain,Neoplasms, Brain, Benign,Neoplasms, Brain, Malignant,Neoplasms, Brain, Primary,Primary Brain Neoplasms,Primary Malignant Brain Neoplasms,Primary Malignant Brain Tumors,Benign Brain Neoplasm,Benign Brain Neoplasms,Benign Neoplasm, Brain,Brain Benign Neoplasm,Brain Benign Neoplasms,Brain Cancers,Brain Malignant Neoplasm,Brain Malignant Neoplasms,Brain Metastase,Brain Neoplasm,Brain Neoplasm, Benign,Brain Neoplasm, Malignant,Brain Neoplasms, Primary,Brain Tumor,Brain Tumors, Recurrent,Cancer, Brain,Intracranial Neoplasm,Malignant Brain Neoplasm,Malignant Brain Neoplasms,Malignant Neoplasm, Brain,Neoplasm, Brain,Neoplasm, Intracranial,Primary Brain Neoplasm,Primary Brain Tumor,Primary Brain Tumors,Recurrent Brain Tumor,Recurrent Brain Tumors,Tumor, Brain
D003593	Cytoplasm	The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)	Protoplasm,Cytoplasms,Protoplasms
D003958	Diamide	A sulfhydryl reagent which oxidizes sulfhydryl groups to the disulfide form. It is a radiation-sensitizing agent of anoxic bacterial and mammalian cells.	Diazodicarboxylic Acid Bis(N,N-dimethyl)amide,Diazodicarboxylic Acid Bisdimethylamide,Dizene Dicarboxylic Acid Bis(N,N-dimethylamide),Dizenedicarboxylic Acid Bis(N,N-dimethylamide),Tetramethylazoformamide,Acid Bisdimethylamide, Diazodicarboxylic,Bisdimethylamide, Diazodicarboxylic Acid
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D005033	Ethylmaleimide	A sulfhydryl reagent that is widely used in experimental biochemical studies.	N-Ethylmaleimide,N Ethylmaleimide
D005293	Ferritins	Iron-containing proteins that are widely distributed in animals, plants, and microorganisms. Their major function is to store IRON in a nontoxic bioavailable form. Each ferritin molecule consists of ferric iron in a hollow protein shell (APOFERRITINS) made of 24 subunits of various sequences depending on the species and tissue types.	Basic Isoferritin,Ferritin,Isoferritin,Isoferritin, Basic